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Redox Reactions and Electro Chemistry, , 8, , Electrochemical cell (Galvanic cell) : An apparatus which converts chemical energy into, electrical energy is called electrochemical cell., Principle of electrochemical cell : Conversion of chemical energy into electrical energy., A redox reaction takes place in electro chemical cell. For example, following redox reaction, takes place when metallic strip of zinc is dipped in aqueous soluion of copper sulphate., Zn(s), reactions., , + Cu2+(aq), , Zn(s) U Zn2+(aq), Cu2+(aq), , + 2e-, , U Zn2+, , (aq), , + Cu(s) In reality this reaction is the sum of following two half, , + 2e- (oxidation), , U Cu, , (s), , (reduction), , Above both reactions occur in a same container. But these reactions can be made to occur in, two different containers as follows., -, , -, , e, , e, G, , +, , Zn anode, , Cu cathode, Salt bridge, soln of, NH4NO3 or, KNO 3, , aq. ZnSO4, , aq. CuSO4, Cotton, plugs, , Metallic strips dipped in solution are called electrodes., The strip on which oxidation takes place is called anode and that on which reduction takes place is, called cathode., On connecting both the electrodes by copper wire electrons flow from anode (Zn) to cathode (Cu), in external circuit., The conduction of electricity in solution is by ions and that in external circuit is by electrons., The flow of electric current in external circuit is from cathode (Cu) to anode (Zn)., Salt-bridge : The U shaped glass tube connecting two solutions of electrochemical cell and filled, with proper electrochemical cell and filled with proper electrolytic solution (NH4NO3) is called salt-bridge., Function of salt bridge : It connects two solutions of electrochemical cell and maintains its, electrical neutrality. Besides this, it completes the electrical circuit of the cell., 177

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Types of electrodes :, The three main types of electrodes are as follows :, (1) Active metal electrodes : eg. Zn, Ag, Cu, Al etc., (2) Inert electrodes of metal or non-metals eg. Pt (metal), steel (alloy), graphite (non-metal) etc., (3) Gas electrodes : eg. H2, Cl2 etc., Half-cell : An electrode and a solution in which it is dipped are collectively known as half-cell., Standard half-cell : If concentration of a solution of half cell is 1 M or the pressure of a gas, is 1 atmosphere and temperature is 25° C, then such a half-cell is termed as standard half cell., Standard cell : A standard cell is formed by connecting two standard half-cells., Symbolic representation of electrochemical cell : Anode is shown at left hand side and cathode, is shown at right hand side., For example, Zn | Zn2+(C ) || Cu2+(C ) | Cu For standard cell, Zn | Zn2+(1.0 M) || Cu2+(1.0M) | Cu 25o C, 2, , 1, , Similarly, symbollic representation involving gas electrode as one of the half-cell is :, Pt | H2(1, , atmosphere), , | H+(C ) || Cu2+(C ) | Cu., 1, , 2, , For the same cell under standard state,, Pt | H2(1 atmosphere) | H+(1.0 M) || Cu2+(1.0 M) | Cu 25o C, Cell potential : In electrochemical cell, when two electrodes are joined the electrons flow, from anode to cathode in external circuit due to electrical pressure produced from chemical reaction., This electrical pressure is called cell potential. (Ecell), If cell is in standard condition then it is called standard cell potential (E0cell)., Voltmeter does not measure the true potential of cell therefore potentiometer is used to, measure the true cell potential., In reality, the cell potential is a measure of difference of intensities of tendencies of two, electrodes to release (or gain) electrons., The absolute value of intensity of tendency of an electrode to release electrons cannot be measured., Because a single half-cell cannot produce electric current and it cannot complete a redox reaction., E.M.F. Series : A cell potential measured with respect to standard hydrogen electrode is, called electromotive force (E.M.F.) of the electrode joined with standard hydrogen electrode., When different electrodes are arranged in decreasing order of their standard reduction, potentials, the resulting series is called emf series., Following informations are obtained from emf series., (1) The tendency to undergo oxidation, to release electrons and strength to act as reducing, agent increases moving down the series., (2) The tendency to undergo reduction, to accept electrons and strength to act as oxidizing, agent decreases moving down the series., (3) The standard cell potential of a cell constructed by joining any two half cells can be, calculated from this series., (4) Which electrode would act as cathode and which would act as anode can be predicted., The cell potential of electrochemical cell depends on nature of electrode, temperature of cell, and concentration of solution., 178

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1., , 2., , When copper strip is dipped in aqueous solution of silver nitrate, ....., (A) solution becomes colourless., (B) intensity of blue colour increases., (C) intensity of blue colour decreases., (D) chemical reaction does not take place., What is observed when zinc strip is dipped in aq. solution of CuSO4 ?, (Atomic mass of Zn is more than that of Cu)., , 3., , (A) The intensity of blue colour of solution decreases., , (B) The mass of zinc strip increases., , (C) The intensity of blue colour of solution increases., , (D) None of the given., , What is not observed when zinc strip is placed in aq. solution of CuSO4 ?, (Atomic mass of Zn is more than Cu), (A) The colour of surface of zinc strip is changed., (B) The mass of zinc strip decreases., (C) The mass of zinc strip increases, (D) The intensity of blue colour of solution decreases, , 4., , What is the observation when Zn-rod is dipped in aq. CuSO4 ?, (Atomic mass of Zn is more than Cu), (A) The intensity of blue colour of solution decreases., (B) The mass of zinc rod increases., (C) The concentration of SO24- ions in solution increases., (D) The concentration of SO24- ions in solution decreases., , 5., , What is observed when copper rod is dipped in aq. AgNO3 ?, (Atomic mass of Ag is more than Cu) ?, (A) The mass of copper rod does not change., (B) The mass of copper rod decreases., (C) Solution becomes blue gradually., (D) The colour of surface of copper rod does not change., , 6., , 7., , 8., , What is not observed when Cu rod is dipped in aq. AgNO3 ?, (A) The mass of copper rod increases., , (B) The mass of copper rod decreases., , (C) Solution becomes blue gradually., , (D) Ag deposits on surface of Cu., , When Zn strip is dipped in Cu(NO3)2 ....., (A) Zn undergoes reduction., , (B) Zn undergoes oxidation., , (C) Cu undergoes reduction., , (D) Cu undergoes oxidation., , Zn rod is dipped in 1.5 L aqueous solution of 0.1M CuSO4. Choose correct option for following statements doing theoretical calculations., (Atomic mass : Zn = 65 gm mole–1 and Cu = 63.5 gm mole–1) T = True, F = False., (i), , 13 gram Zn dissolves when its mass decrease by 0.3 gram., , (ii) Concentration of Cu2+ becomes 0.08 M when 1.95 gram Zn dissolves., (iii) number of Zn 2+ ions is 4.5165 ´ 1024 when molarities of Cu2+ and Zn2+ are equal in solution., (iv) The molarity of Zn2+ is 0.04 M when 3.6132 ´ 1022 Cu atoms deposit., 179

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(A) TTTF, 9., , (B) FFFT, , (C) TTFT, , (D) FFTT, , Which observations are true when Zn strip is dissolved in aq. Cu(NO3)2 ?, (i) Blue colour of solution fades gradually., (ii) Concentration of NO3- ions in solution decrease gradually., (iii) Concentration of Zn2+ ions in solution increase gradually., (iv) Cu2+(aq) ions are displaced by Zn2+(aq) ions in solution., (A) (i), (ii), , 10., , (B) (ii), (iii), , (C) (i), (iii), (iv), , (D) (i), (iv), , Which option is incorrect for a stoichiometric reaction taking place according to following diagram ?, (Atomic mass : Al, , = 27 gm mole–1 and Ag = 108 gm mole–1), , Al strip, , (A) For reduction of all Ag+ ions in solution, 90, gram Al is required., (B) 648 gram Ag+ ions are reduced by 54 gram, Al, (C) If 81 gram Al is reduced, then 972 gram Ag+, , 5 litre, 2.0M, AgNO3, , ions will be left unreacted in solution., (D) During oxidation of 2 mol Al, 3.6132, , ´ 1024, , Ag+ ions will reduce., 11., , Zn strip is dipped in 1.5 L aqueous solution of 0.1 M CuSO4. Choose correct option with reference, to following statements. (Atomic mass : Zn = 65 gm mole–1 and Cu = 63.5 gm mole–1), (i) When 13 gram Zn dissolves 12.7 gram Cu deposits and there is increase of 0.3 gram in mass of, strip., (ii) When there is decrease of 0.02 M in concentration of Cu2+, 1.3 gram Zn dissolves., (iii) When molarities of Cu2+ and Zn2+ are equal, the number of Zn2+ ions is 3.011, , ´ 1022, , in solution., (iv) When 3.6132, (A) (iv), 12., , +3, , (C) (ii), (iv), , (D) (i), (iv), , (B), , -2, , (C), , +4, , (D), , -3, , In which of the following compound oxidation number of oxygen is zero ?, (A) HOCl, , 14., , (B) (ii), , Which carbon having following oxidation number is not there in methyl acetate (CH3COOCH3, OR C3H6O2) ?, (A), , 13., , ´ 1022 Cu atoms deposit, molarity of Zn2+ ions is 0.04 M., , (B) HOF, , (C) HOI, , (D) HOBr, , In a compound containing Xe and F, xenon is 53.85% by mass. State the oxidation number of Xe in, compound. (Atomic mass : Xe = 133, F = 19)., (A), , +2, , (B) 0, , (C), 180, , +4, , (D), , +6

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15., , How many moles of Ag2S would have been consumed theoretically when 1.93 ´ 106 coulomb of, electricity is associated with a redox reaction Ag2S + CN- + O2, Ag(CN)-2 + S in basic medium ?, -, , (1 mole e, , = 96500 coulomb), , (A) 10, 16., , ®, , (B) 2, , (C) 8, , (D) 4, , Choose correct option from following statements with reference to emf series., (A) electron accepting tendency increases moving down., (B) Strength to act as oxidizing agent decrease moving upward., (C) Tendency of undergoing oxidation increase moving down., (D) If rod of metal present downward is immersed in a solution of salt of metal present upward in, a series, then it does not dissolve., , 17., , Which electrolyte cannot be used in salt bridge of an electrochemical cell : Fe | Fe2+(1.0 M) || Ag+(1.0 M) | Ag ?, (B) NaCl, , (A) KNO3, 18., , (C) NH4NO3, , (D) NaNO3, , If standard reduction potentials of half cells : X2+ |X, Y2+|Y, Z2+| |Z and W2+|W are in increasing order then, select correct option from following statements. (T = true statement, F = False Statement), (i) rod of metal X dissolves in solution of Y2+., (ii) solution of X2+ cannot be filled in container of metal Z., (iii) reaction W(s), , + Y2+(aq 1.0 M), , U W2+, (aq 1.0 M), , + Y(s) is spontaneous in forward direction., , (iv) metal atoms Z cannot displace Y2+(aq) ions from solution of Y2+ ions., (A) TFFT, 19., , >Y>Z, , (B) X, , >Z>Y, , (C) Z, , >Y>X, , >B>C>D, , (B) D, , >B>C>A, , (C) D, , >C>A>B, , (D) Z, , >X>Y, , (D) B, , >A>C>D, , If standard oxidation potentials of M | M2+, N | N2+, Q | Q2+ and R | R2+ half cells are in increasing, order then which of the given statement is correct ?, (A) Solution of a salt of M2+ can be stored in vessel of metal N., (B) Solution of a salt of R2+ cannot be stored in vessel of metal Q., (C) Solution of a salt of R2+ can be stored in vessel of metal N., (D) All given three statements are wrong., , 22., , (D) TFTF, , At 25° C under standard state conditions, (i) On dipping metallic rod of A in B2+(aq) metal A does not, dissolve. (ii) aqueous solution (C2+(aq)) of metallic salt of C, cannot be filled up in a vessel of metal, A. (iii) on dipping a spoon of metal C in (D2+(aq)) metal deposits on spoon. (iv) Give correct order of, metals as reducing agents., (A) A, , 21., , (C) FTFT, , Aq. solution of a salt of metal Y can be filled up in a vessel of a metal X and aq. solution of a salt, of metal Z can be filled up in a vessel of a metal Y. Which of the given decreasing order of X, Y, and Z as reducing agent is correct ?, (A) X, , 20., , (B) FTTF, , On what does cell potential of electrochemical cell not depend ?, (A) Concentration of solution associated with cell reaction., (B) Substance present in salt bridge., (C) temperature, (D) nature of electrode, 181

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23., , When electrochemical cell Fe | Fe2+(C ) || Cu2+(C ) | Cu is operating, then ......., 2, , 1, , (A) oxidation potentials of half cells at L.H.S. and R.H.S. increases gradually., (B) oxidation potential of half cells at L.H.S. and R.H.S. decreases gradually., (C) oxidation potential of half cell at L.H.S. decrease while that of at RHS increase gradually., (D) reduction potential of half cell at L.H.S. and oxidation potential of half cell at RHS decrease, gradually., 24., , Which instrument measures cell potential accurately ?, (A) ameter, , 25., , 26., , (B) voltmeter, , (C) galvanometer, , (D) potentiometer, , The potential of a cell constructed by joining a std. half-cell with S.H.E. by salt bridge is measured, using potentiometer. If S.H.E. is cathode, then measured potential is equal to ......, (A) E0red of another electrode, , (B) E0ox of another electrode, , (C) Eox of another electrode, , (D) Ered of another electrode, , Select true and false statements with respect to electrochemical cell., Where, T, , True Statement and F, , =, , =, , False statement, , (i) electricity is conducted from anode to cathode in external circuit., (ii) electricity is conducted by ions in solution., (iii) negative ions at anode move towards solution at cathode through salt bridge., (iv) electrons flow from cathode to anode in external circuit., (A) FFFT, , (B) FTFF, , (C) TFTF, , (D) FTTF, , Answers : 1. (B), 2. (A), 3. (C), 4. (A), 5. (C), 6. (B), 7. (B), 8. (C), 9. (C), 10. (C),, 11. (A), 12. (C), 13. (B), 14. (D), 15. (A), 16. (C), 17. (B), 18. (A), 19. (C),, 20. (D), 21. (C), 22. (B), 23. (C), 24. (D), 25. (B), 26. (B), Nernst equation : An equation showing relation between cell potential of non standard, electrochemical cell and concentration of solution associated with cell reaction at definite, temperature is called Nernst equation., This equation can be derived on the basis of principles of thermodynamics., D, , -, , G, , G0 + RTlnQc But, , = D, , nFEcell, , G, , nFE0cell + RTlnQ, , = -, , At 298 K, the value of, \, , D, , = -, , nFEcell and, , So, Ecell = E0cell -, , =, , nFE0cell Substituting these values in equation,, , = -, , RT, lnQc, nF, , 2.303RT 2.303 × 8.314 × 298, ,, F, 96500, , Nernst equation at 298 K Ecell = E0cell -, , cell reaction, Qc, , G0, , D, , =, , 0.059, logQc. Where, n, n, , eg. For a cell, Zn | Zn2+(C ) || Ag+(C ) | Ag, cell reaction is :, 2, , 182, , =, , E0cell, , -, , 2.303RT, logQc, nF, , 0.059 V., , Product of concentration of products, Product of concentration of reactants, 1, , Therefore Ecell, , =, , change in oxidation number in

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Zn(s), , + 2Ag2+(aq), , U Zn2+, (aq), , +, , 2Ag(s), , Nernst equation for above cell reaction is as follows :, 0, , Ecell = E cell -, , 2.303RT, nF, , ., , log, , [Zn, , 2+, , 2+, , ], , 0, , Therefore at 298K temprature Ecell = E cell -, , [Ag + ]2, , [Zn ], 0.0592 ., log, n, [Ag + ]2, , where n = Change in oxidation numbner of rejaction in balanced equation of cell reaction or number of moles of, , = 2. \ At 298 K temperature Ecell =, , electrons associated with reaction. Here n, , 2+, , E0cell -, , [Zn ], 0.0592 ., log, 2, [Ag + ]2, , With the help of Nernst equation half cell potential of non standard half cell also can be calculated., eg., oxidation potential of Ni | Ni2+ half cell is given by writing oxidation reaction., Ni(s) U Ni2+(aq), , + 2e-., , n, , =2, , \ ENi | Ni2 = E0Ni | Ni2, +, , +, , -, , 0.0592 ., log[Ni2+], 2, , In order to determine reduction potential of Ni/Ni2+ half cell reduction half reaction is written as :, Ni2+(aq), , + 2e, , -, , U Ni, , n, , (s), , =2, , ENi2, , +, , = E0Ni2, | Ni, , +, , | Ni, , -, , 1, 0.0592 ., log [N 2+ ], 2, i, , Concentration cell : An electrochemical cell made up of two same electrodes but having different, concentrations of electrolytic solutions is called concentration cell., eg. Ag | Ag+(C ) || Ag+(C ) | Ag (C1 < C2) In this cell, ions move from a solution containing higher, 2, 1, concentration to a solution having lower concentration., anode : Ag(s) U Ag+(aq)(C1), , + e-, , cathode : Ag+(aq)(C2), , +e, , Cell reaction : Ag, , (C2) U Ag, , -, , +, , U Ag, (s), , (aq), , +, , (C1), , (aq), , For this cell, n = 1 and E°cell = 0.0V, C1, 0.059 ., log C, n, 2, , \, , Ecell = E0cell -, , \, , Ecell = 0 -, , \, , Ecell = 0.059.log C, , C1, 0.059 ., log C, 1, 2, C1, 2, , The potential of concentration cells are relatively low. Because E0cell = 0.0 V. When the cell is, operating, ions of a concentrated solution move towards dilute solution and when concentrations of both the, solution is equal Ecell = 0.0 V., The equilibrium constant for concentration cell is “1”., 183

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27., , (A) 0.007 V, 28., , (B) 0.01587 V, , (B) volt, , (C) faraday, , (D) has no unit, , = E0red(anode) + E0red(cathode), , (B) E0cell, , = E0oxi(cathode) + E0oxi(anode), , (C) E0cell = E0oxi(cathode) - E0oxi(anode), , (D) E0cell, , = E0red(anode) + E0oxi(cathode), , What is the value of Q if n = 3 taken for the cell : Al | Al3+(0.02M) || Pb2+(0.2M) | Pb ?, (A) 0.05 M–1, , 31., , (D) 0.07 V, , Which equation is appropriate to find E0cell ?, (A) E0cell, , 30., , (C) 0.01857 V, , Give the unit of a value 0.059 obtained in Nernst equation at 25o C., (A) coulomb, , 29., , 2.303RT, in Nernst equation at 80° C ?, F, , What is the value of a term, , (B) 0.2236 M, , −1, 2, , (D) 0.05 M, , (C) 0.01 M, , Which Nernst equation is correct for a cell : Co | Co2+(C ) || Ag1+(C ) | Ag ?, 1, , + 2, , [Ag ], , (A) E0cell = Ecell +, , RT ., ln, 2F, [Co 2 + ], , (C) E0cell = Ecell -, , RT . [Co ], ln, 2F, [Ag + ]2, , 2, , 2+, , (B) E0cell = Ecell +, , RT ., ln, +, F, [Ag ], , (D) E0cell = Ecell +, , RT . [Co ], ln, F, [Ag + ]2, , 2+, , Which Nernst equation is correct for finding oxidation potential of Ni|Ni2+ half cell ?, , -, , RT ., ln[Ni2+], 2F, , (B) ENi|Ni2+ = E0Ni|Ni2+, , (C) E0Ni|Ni2+ = ENi|Ni2+ +, , RT ., ln[Ni2+], 2F, , (D) E0Ni|Ni2+, , (A) E0Ni|Ni2+ = ENi|Ni2+, , 33., , 1, , [Co ] 2, , 2+, , 32., , −1, 2, , +, , RT ., ln[Ni2+], 2F, , - ENi|Ni2+ =, , 1, RT ., l 2+, 2F [Ni ], , Which option is proper for the value of Q for given value of n for the cell :, Zn | Zn2+(0.005M) || Ag+(0.04M) | Ag ?, , 34., , (A) n, , = 1, Q = 3.125, , (C) n, , = 3, Q = 5.5243 M, , M, , −1, 2, , −3, 2, , (B) n, , = 2, Q = 1.7677 M, , (D) n, , = 4, Q = 0.156 M–2, , Which option is true for the values of n and Q for the cell : Pt | Br2(l ) | Br-(C ) || Au3(C+ ) | Au ?, 1, , (A) n, , =, , (C) n, , =, , 3, Q, 6, Q, , =, , =, , 3+, , -, , 3, , 3+ 2, , -, , 6, , [Au ][Br ], , (B) n, , =, , 6, Q, , =, , [Au ] [Br ], , [Au 3+ ]2 [Br − ]6, 1, , (D) n, , =, , 3, Q, , =, , 1, [Au 3+ ][Br − ]3, , 184, , 2

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35., , 36., , 20 M-4 for the cell; Pt | Cl2(g.1.0bar) | Cl-(0.5M) || Au3+(0.4M) | Au then .......... ., , If Qc, , =, , (A) n, , =6, , (B) n, , (B) 0.0282 V, , =3, , (D) n, , =4, , (C) 0.616 V, , (D) 0.649 V, , If EZn2+(XM)|Zn < EoZn2+|Zn what is the possible value of x ?, (A) 1.2 M, , 38., , (C) n, , Give the oxidation potential of a half cell : Pt | H2(g.1.0bar) | H+(pOH = 11) at 25°C., (A) 0.177 V, , 37., , =2, , (B) 0.2 M, , (C) 1.0 M, , (D) cannot be determined, , The actual potential of a cell Fe | Fe2+(xM) || Ag+(yM) | Ag is 1.295 V at 25o C. If potential of, , Fe2+(XM) | Fe is 0.455 V at 25°C, what will be the potential of Ag+(yM) | Ag half cell at the same, temperature ?, (B) -2.135 V, , (A) 0.84 V, 39., , For a reaction Co(s), , + 2Ag+(aq), , (C) 3.125 V, , U Co2+, (aq), , (D), , -0.84 V, , + 2Ag(s), E0cell = 1.08 V. What will be the change in, , E0cell if concentration of Co2+(aq) is doubled ?, (A) doubles, , 40., , (B) halves, , (C) no change, , (D) increase less than half, , When will the cell potential of electrochemical cell be zero ?, (A) When EOX(anode) = Ered(Cathode), (B) When E0red(anode) = E0red(cathode), (C) When EOX(anode) = EOX(cathode), (D) When concentration of solution of both half cells are equal., , 41., , 42., , For given options when will Ecell = E0cell in electrochemical cell ?, , =1, , (A) Only when concentrations of both half-cells are same, , (B) If K, , (C) When cell reaction reaches equilibrium, , (D) None of the given, , If Ecell = E0cell for a cell Zn | Zn2+(0.04M) || Ag+(C ) | Ag, then what is the value of C2 ?, 2, , (A) 0.04M, 43., , (B) 0.02M, , (C) 0.2M, , (D) 0.0016M, , What will be the change in cell potential when concentration of cathode solution is increased in a, cell Fe | Fe3+(C ) || Cl-(C ) | Cl2(g) | Pt at definite temperature ?, 1, , (A) increase, 44., , 2, , (B) decrease, , (C) no change, , (D) Ecell, , = E0cell., , When identical decrease of 0.1 M is done in concentration of both the solution in a cell, Mg | Mg2+(C ) || Fe2+(0.5M) | Fe at definite temperature then what will be the value of C1 ?, 1, , (A) 0.7 M, 45., , (B) 0.5 M, , (C) 0.4 M, , (D) none of the given, , What will be the change in cell potential if concentration of both half cell solutions is decreased by, 0.1 M in a cell : Co | Co2+(C ) || Sn2+(C ) | Sn ; C2 > C1 ?, 1, , (A) increase, 46., , 2, , (B) decrease, , (C) No change, , (D) Ecell, , = E0cell, , What will be the value of C1 if cell potential is increases on increasing concentration of both solutions, by 0.1M in a cell Ni | Ni2+(C ) || Cu2+(0.4M) | Cu at definite temperature ?, 1, , (A) 0.8 M, , (B) 0.1 M, , (C) 0.4 M, 185, , (D) none of the given

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47., , What will be the change in cell potential if concentration of both half cell solutions is decreased by, 0.1 M in a cell : Cd | Cd2+(C ) || Cu2+(C ) | Cu ? (C1 and C2 > 0.1 M), 2, , 1, , (A) increase, 48., , 49., , (B) 2OH-(aq) U H2(g) + O2(g) + 2e-, , (C) 2H2O(1) + 2OH-(aq) U 3H2(g) + 2e-, , (D) H2(g) + 2OH-(aq) U 2H2O(1) + O2(g) + 2e-, , Which cell representation is not proper according to the actual cell reaction occuring in the cell at, 25o C ?, = -, , 0.13V, E0Sn2+ | Sn, , (C) Pb | Pb2+(0.01M) || Sn2+(0.1M) | Sn, , (D) Sn | Sn2+(0.05M) || Pb2+(0.5M) | Pb, , The cell potential of a cell constructed by joining Ag | Ag+(0.4M) and Al | Al3+(0.1M) half cells at, 25° C, is 2.456 V then what will be standard cell potential ?, (B) 2.46 V, , (B) decrease, , (C) no change, , (D) cannot be said, , (B) decrease, , (C) no change, , (D) cannot be said, , On decreasing the temperature of a cell : Mg | Mg2+(c M) || Fe2+(0.08M) | Fe the cell potential, increases theoretically, then what is the possible value of C ?, , = 0.5, , (B) C, , = 0.02, , (C) C, , = 0.05, , (D) C, , On decreasing the temperature of a cell : Zn | Zn2+(C ) || Sn2+(C ) | Sn (C1, 2, 1, theoretical change in cell potential ?, (B) decrease, , (C) no change, , The values of Ecell and E0cell at 25o C are 2.3629 V and 2.36 V, Mg | Mg, , 2+, , (0.2M), , (A) 0.4 M, 56., , (D) 2.76 V, , What will be the theoretical change in cell potential of a cell Zn | Zn2+(0.05M) || Co2+(0.08M) | Co when, its temperature is increased ?, , (A) increase, 55., , (C) 2.64 V, , What will be the theoretical change in cell potential of a cell Ni | Ni2+(0.001M) || Ag1+(0.01M) | Ag when, its temperature is increased ?, , (A) C, 54., , 0.14V), (B) Sn | Sn2+(0.02M) || Pb2+(0.2M) | Pb, , (A) increase, 53., , = -, , (A) Sn | Sn2+(0.1M) || Pb2+(0.01M) | Pb, , (A) increase, 52., , (D) cannot be said, , (A) H2(g) + 2OH-(aq) U 2H2O(1) + 2e-, , (A) 1.46 V, 51., , (C) no change, , Give oxidation reaction of Pt | H2(g.1.0bar) | OH-(aq) half cell., , (E0Pb2+ | Pb, , 50., , (B) decrease, , || H, , +, , (XM), , | H2(g.1.0 bar) | Pt, then X, (B) 0.5 M, , =, , = 0.04, , < C2), what will be, , (D) cannot be said, respectively for a cell :, , .........., , (C) 0.1 M, , If standard cell potential of a reaction 2H2O(l) U O2(g.1.0 bar), , (D) 0.25 M, , + 4H+(aq) + 4e- is -1.23V at 25o C, , and [H+] = 10–7 M, then what will be the potential of this cell ? or what will be the oxidation, potential of pure water at 25°C ?, (A) -0.41 V, , (B) -2.62 V, , (C) -0.817 V, 186, , (D) 0.41 V

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57., , At 25o C, for a reaction 2H2O(l) + 2e U H2(g.1.0 bar) + 2OH-(aq.10–7M) E, -, , 0.417 V or If reduction, , = -, , potential of pure water is -0.417 V then what will be the E° of this reaction ?, (A), 58., , -, , 0.83 V, , -, , 2.62 V, , (C), , What are Ecell and K eq respectively of Fe(s), (E0Fe2+|Fe = 0.44 V, E0Ag+|Ag = 0.80 V), (A) 1.25V, 1.04, (C) 1.23V, 1.264, , 59., , (B), , E0Cr3+/Cr, , = -, , ´, ´, , +, , -, , 2Ag, , 0.817 V, , +, , (aq.0.5M), , (D) 0.41 V, , U Fe 2+, (aq.0.1M), , +, , 1021 M–1, , (B) 1.23V, 1.507, , ´, , 1012 M–1, , 106 M–1, , (D) 1.25V, 1.081, , ´, , 1042 M–1, , 0.74 V, E0MnO –/Mn3+, , =, , 4, , 1.51 V, E0Cr O2–/Cr3+, , =, , 2 7, , 1.33 V and E0Cl/Cl–, , =, , 2Ag (s) at 25°C ?, , 1.36 V, which of the, , following is strongest oxidizing agent according to given data ?, (A) Cr3+, ˆ, , (B) Mn2+, , (C) MnO4–, , (D) Cl, , –, , Applications of cell potential., (1) Keq can be calculated., (2) KSP (solubility product of sparingly soluble salts), pH of acids and ionic product of water (KW), can be calculated., (3) Certain titrations can be carried out using cell potential., (4) Spontainity of a reaction can be determined using cell potential., , 60., , What is the E° cell of reaction if equilibrium constant K, Cd(s) + Sn2+(aq) U Cd2+(aq) + Sn(s) at 298 K temperature ?, (R, , = 8.314 J mol–1 K–1, F = 96500 couloub mol–1), , (A) 0.52 V, 61., , (C) 0.32 V, , (D) 3.16 V, , (B) 1.66 V, , (C) 2.71 V, , 8, , (D) 3.16 V, , (B) 2, , (C) 3, , =, , (D) 4, , What will be the oxidation potential of Pt | H2(g.1.0 bar) | H+(aq. pH = 4) at 25o C ?, (B) 0.649 V, , (C) 0.236 V, , (D), , -0.118 V, , The oxidation potenital of hydrogen half cell at 25o C temperature and 1.0 bar pressure is 0.118 V., What will be the pOH of its solution ?, (A) 2, , 66., , (B) 0.1186 V, , = 1.3141 ´ 10107 M–1 and n = 2, , The E° cell of an electrochemical cell is 3.16 V at 25 o C and value of Kc, 1.727 ´ 10214 M–2 then give value of ‘n’ for cell reaction., , (A) 0.118 V, 65., , (D) 0.48 V, , For a reaction occuring in an electrochemical cell Kc = 1.3141 ´ 10 M and n = 6. If standard reduction, potential of cathode is 1.36 V, then what will be the standard oxidation potential of anode ?, , (A) 1, 64., , (C) 0.13 V, , 307, , (A) 6.32 V, 63., , (B) 0.26 V, , For a reaction occuring in an electrochemical cell at 25o C, Kc, then E0cell for cell will be ?, (A) 6.32 V, , 62., , = e 20.2537 (n = 2) of a reaction,, , (B) 3, , (C) 5, , (D) 12, , 2, The Ecell of Pt | H2(g.1.0 bar) | HCl(XM) || Cu+(0.01, | Cu is 0.635 V at 25°C. What will be the pH of, M), , HCl ? (E0Cu+2|Cu, (A) 2.0, , = 0.34 V), , (B) 5.0, , (C) 6.0, 187, , (D) 4

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67., , The Ecell of Mg | Mg2+(0.01 M) || HCl(XM) | H2(g.1.0 bar) | Pt is 2.09V at 25°C. What will be the pH of, HCl ? (E0Mg2+|Mg, (A) 6.58, , 68., , (B) 5.58, , (B) 4.17, , (C) 5.5, , (D) 4.83, , What is the potential of a cell : Pt | H2(g.1.0 bar) | OH-(aq.pH = 4.5) || H+(aq.pH = 2.5) | H2(g.1.0 bar) | Pt at 298 K ?, (A) 0.118 V, , (B) 0.205 V, , (C) 0.08 V, , (D) 0.124 V, , What is the potential of a cell : Pt | H2(g.1.0 bar) | OH-(aq.pOH = 10.5) || H+(aq.pH = 2.0) | H2(g.1.0 bar) | Pt at 298 K?, (A) 0.5015 V, , 71., , (D)4.58, , = 1.40 V), , (A) 3.5, , 70., , (C) 3.58, , The Ecell of Pt | H2(g.1.0 bar) | HCl(XM) || Au3+(0.001 M) | Au is 1.6655 V. What will be the pH of HCl ?, (E0Au3+|Au, , 69., , 2.36 V), , = -, , (B) 0.0885 V, , (C) 0.0452 V, , (D) 0.05015 V, , Which reaction will be spontaneous in forward direction at 25o C ? The standard oxidation potentials, of Pt | I2(s) | I-, Cu | Cu2+, Cr | Cr3+, Zn | Zn2+, Sn | Sn2+, Pb | Pb2+, Ag | Ag+ and Fe | Fe3+ are, , -0.54 V, -0.34 V, 0.74 V, 0.76 V, 0.14 V, 0.13 V, -0.80 V and 0.037 V respectively., (A) 2I-(aq. 0.1 M) + Cu2+(aq. 0.05 M) U I2(s) + Cu(s), (B) 2Cr3+(aq. 0.001 M) + 3Zn(s) U 2Cr(s) + 3Zn2+(aq. 0.1 M), (C) Pb2+(aq. 0.02 M) + Sn(s) U Pb(s) + Sn2+(aq. 0.2 M), (D) 3Ag(s) + Fe3+(aq. 0.01 M) U 3Ag+(aq. 0.1 M) + Fe(s), 72., , +, , +, , E0red of Fe | Fe2 and Fe | Fe3 are, , -0.44 V and +0.77 V respectively. What is the E0OX value of, , +, , Fe | Fe3 ?, (A) 0.037 V, 73., , If E0Cu|Cu2+ =, (A), , 74., , -, , (B) 0.33 V, 0.34 V and E0Cu2+|Cu+ =, , -, , 0.12 V, , (B), , -, , (C), , -, , 0.33 V, , (D), , -, , 0.11 V, , 0.16 V then what is the value of E0Cu|Cu+ ?, , +, , 0.48 V, , (C), , +, , 0.48 V, , (D), , -, , 0.52 V, , Standard oxidation potential of Co | Co3+, Co2+ | Co3+, Fe | Fe3+ and Fe2+ | Fe3+ are -0.4167 V, -1.81 V,, +, , +, , 0.0367 V and -0.77 V respectively. What will be the standard cell potential of Fe | Fe2 || Co2 | Co?, (A) 0.72 V, 75., , (B), , -0.11 V, , (C) 1.0 V, , (D) 0.16 V, , The value of E0OX of Pt | H2(g.1.0 bar) | OH-(aq) half cell at 50° C temperature is, , +0.83 V, then what, , will be the value of ionic product (KW) of water at 50° C ?, (A) 1.12, 76., , ´ 10-13, , (B) 1.102, , ´ 10-12, , (C) 1.105, , ´ 10-12, , (D) 1.0, , ´ 10-14, , What will be the oxidation potential of half cell at L.H.S. in a cell Sn | Sn2+(0.1 M) || Pb2+(0.5 M) | Pb at, 25°C when equilibrium is established ? (E0Sn2, (A) 0.128 V, , +, , | Sn, , (B) 0.0 V, , = -, , 0.14V, E0Pb2, , (C) 0.114 V, 188, , +, , | Pb, , = -, , 0.13 V), , (D) 0.151 V

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77., , What, , will, , be, , the, , (E0Co2, , +, , | Co, , 0.28 V and, , = -, , (A) 97.82 %, 78., , decrease, , U Co2+, (aq 0.01 M), , + Ni2+(aq 0.1 M), , Co(s), , %, , -, , in, , concentration, , Ni 2 + (aq), , of, , when, , a, , reaction, , + Ni(s) at 25° C comes to an equilibrium ?, , 0.23 V), , (B) 8.74 %, , (C) 95.4 %, , An excess of liquid mercury is added into a solution of 1.0, , ´, , (D) 92.5 %, 10-3 M Fe3+. At 25°C temperature 5%, , Fe3+ is left at equilibrium. If only following reaction is possible, then what will be the value of, E0Hg2, , +, , | Hg, , ? (E0Fe3, , +, , + 2Fe3+(aq), , 2Hg(l), , | Fe2+, , = 0.77 V), , U Hg 2+, 2, , (A) 0.793 V, 79., , (aq), , + 2Fe2+(aq), , (B) 0.643 V, , (C), , -0.793 V, , What will be the values of reduction potentials of anode and cathode when equilibrium is established, in electro chemical cell : Fe | Fe2+(0.1 M) || Cd2+(0.5 M) | Cd at 25°C ? (n, E0Cd2+| Cd, (A), , 80., , -0.643 V, , (D), , = -, , = 2). E0Fe2+| Fe, , 0.44 V,, , = -, , 0.40 V., , 0.477 V, , (B) +0.477 V, , -, , (C), , -, , 0.447 V, , (D), , -, , 0.575 V, , The reaction occuring in a following cell is in equilibrium at 298 K, then which option is appropriate ?, Zn | Zn2+(XM) || Cu2+(yM) | Cu, (A) EZn | Zn2+, , =, , (C) EZn | Zn2+, , =, , (XM), , (XM), , 81., , ECu2+, , -, , (yM) | Cu, , (B) EZn | Zn2+, , = -, , (D) EZn | Zn2+, , +, , ECu | Cu2+, , (XM), , ECu2+, , (yM) | Cu, , (yM), , ECu2+, , (yM) | Cu, , (XM), , =, , 0.0 V, , The reaction occuring in a cell Co | Co2+(1.0 M) || Ni2+(XM) | Ni at 298 K is in equilibrium, then x, .........., E0Co2+| Co, , = -, , 0.28 V and E0Ni2+| Ni, , (A) 1.0 M, 82., , 0.23 V. (n, , = -, , (B) 1.02 M, , =, , 2), , (C) 0.02 M, , (D) 0.5 M, , The following half-cell reactions are given :, Mn2+, , + 2e- ® Mn; E0 = -1.18V, 2(Mn3+ + e- ® Mn2+); E0, , then what is E° of 3Mn2+, , ® Mn + 2Mn, , 3+, , = +, , 1.51 V, , ? (and decide the spontaneity of a reaction), , (A) -0.33 V; reaction spontaneous, , (B) -2.69 V; non spontaneous reaction, , (C) -2.69 V; reaction spontaneous., , (D), , -0.33 V; non spontaneous reaction, , 31., 40., 49., 58., 67., 76., , (B),, (C),, (A),, (D),, (B),, (D),, , Answsers : 27., 36., 45., 54., 63., 72., 81., , (D),, (A),, (B),, (B),, (D),, (A),, (C),, , 28., 37., 46., 55., 64., 73., 82., , (B),, (B),, (A),, (B),, (C),, (D),, (B), , 29., 38., 47., 56., 65., 74., , (D),, (D),, (A),, (C),, (D),, (D),, , 30., 39., 48., 57., 66., 75., , (B),, (C),, (A),, (A),, (C), (A), 189, , 32., 41., 50., 59., 68., 77., , (C),, (D),, (A),, (C),, (C),, (A),, , 33., 42., 51., 60., 69., 78., , (C),, (C),, (B),, (B),, (A),, (A),, , 34., 43., 52., 61., 70., 79., , (D),, (B),, (B),, (D),, (B),, (C),, , 35., 44., 53., 62., 71., 80., , (C),, (C),, (C),, (B),, (A),, (A),, , =

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Electrolysis : When electric current is passed into electrolytic cell containing aqueous solution of, electrolyte or molten electrolyte with proper electrodes dipped in to it. Redox reaction takes place and, products are obtained at electrodes. This reaction is called electrolysis., Principle of electrolysis : Conversion of electrical energy into chemical energy., ˆ Faraday’s Laws of electrolysis :, (1) First law : The amount of products liberated at electrodes during electrolysis is directly proportional to the quantity of electricity passed through electrolytic cell., m, , µ Q. Therefore m = z.Q, z = electro chemical equivalent, , (2) Second law : When different electrolytic cells containing different electrolytes are connected in, a series and same quantity of electricity is passed through them, the amount of products liberated at, different electrodes is directly proportional to their equivalent weights., m, , µ Eeq. Therefore m = Eeq.Q, Eeq = equivalent weight, Q = quantity of electricity passed., , Modern interpretation of Faraday’s laws :, “The number of moles of products obtained at electrodes by oxidation and reduction half reactions, are stoichiometricelly related to the quantity of electricity passed through electrolytic cell.”, The quantity of electric charge carried by 1 mole electrons is called 1 Faraday. Its symbol is ‘F’., 1 (F), , = 1 mol ´ electronic charge, = (6.022 ´ 1023) ´ (1.602 ´ 1019 coulomb), = 96487 colulomb » 96500 colulomb, , F, , =, , I×t, Faraday, where 1, 96500, , = electric current (ampere), t = time (second), , The products obtained by electrolysis of aq. solution of electrolytes depend on following three, factors., (1) nature of electrodes used (2) concentration of solution (3) emf (electrical pressure), , ˆ Electrolysis of molten NaCl, Electrolysis of molten NaCl using graphite anode and steel cathode gives (Cl2(g)) gas at anode and, (Na(s)) metal at cathode. Reactions are as follows :, Reaction : NaCl(l), , ® Na, , +, (l), , + Cl-(l), , Anode (graphite) : Cl-(l) ®, Cathode (Steel) : Na+(l) + e, , 1, Cl, 2 2(g), -, , ®, , + e-, , Na(s), , ˆ Electrolysis of dilute aqueous NaCl, Electrolysis of dilute aqueous NaCl using inert electrodes like graphite or platinum is in reality, electrolysis of water. As explained below electrolysis of diulte aq. NaCl using inert electrodes gives (O2(g)), gas at anode and (H2(g)) gas at cathode., 190

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At anode : In dilute aq. NaCl, concentration of Cl- is low and hence its oxidation is difficult., Compared to it oxidation of water is easier therefore instead of Cl2 gas, oxygen gas is obtained., (Q Cl-(aq) ®, , 1, Cl + e- E0 =, 2 2(g), , 1.36 V; H2O(l), , -, , ®, , 1, O, 2 2(g), , +, , 2H+(aq), , + 2e- E0 = -1.23 V), , At cathode : Reduction of Na+ is difficult and compared to it reduction of water is easier therefore, instead of Na+, water is reduced and H2 gas is obtained., (Q, E0 =, , Na + (aq), , e, , +, , ®, , -, , Na (s) E 0, , =, , -, , 2.70 V; 2H 2 O (l), , +, , 2e, , -, , ®, , H 2(g), , + 2OH - (aq), , 0.83 V), , -, , Anode : H2O(l), , +, , Cathode : 2H2O(l), , 1, O, 2 2(g), , 2H+(aq) + 2e-, , +, , 2e- + H2(g) + 2OH-(aq), , +, , Cell reaction : 2H+(aq), Net reaction : H2O(l), , 2OH-(aq), , +, , ®, , 1, O, 2 2(g), , ® 2H2O(l), , + H2(g), , Thus electrolysis of dilute aq. NaCl using inert electrodes is in reality electrolysis of water. (The pH, of solution does not change during electrolysis of dil. aq. NaCl using inert electrodes. Phenolphthalin will, not give any colour change and solution will remain colourless during electrolysis. Similarly, methyl orange, will also not show any colour change and as solution is neutral it will remain orange in colour. As amount, of water decreases, concentration of NaCl increases in solution.), ˆ Electrolysis of concentrated aqueous NaCl :, Electrolysis of conc. aq. NaCl using inert electrodes like graphite or platinum gives Cl2(g) gas at, anode and H2(g) gas at cathode as follows., At anode : Concentration of Cl- is higher in conc. aq. NaCl compared to that of H2O and hence, , Cl- is oxidized easily and Cl2(g) gas produce at anode., At cathode : Reduction of Na+ is difficult and that of H2O is comparatively easier and hence at cathode, , water is reduced and H2 gas is obtained. (Q Na+(aq) + e, (aq), , -, , ® Na, , (s), , E0 = -2.70 V; 2H2O(l) + 2e, , -, , ®, , H2(g) + 2OH-, , E0 = -0.83 V), anode : Cl-(aq), , ®, , cathode : 2H2O(l), , 1, Cl + e2 2(g), +, , 2e, , -, , ®, , H2(g) + 2OH-(aq), , In solution Cl-(aq) ions are displaced by OH-(aq) ions., , Thus electrolysis of concentrated aq. NaCl using inert electrodes gives Cl2(g) gas at anode, H2(g) gas, at cathode and NaOH is produced in solution. Thus electrolysis of conc. aq. NaCl is in reality industrial, production of NaOH., (As solution becomes basic by electrolysis of conc. aq. NaCl using inert electrodes the pH of solution, increases. If electrolysis is carried out adding phenolphthalein, solution turns pink from colourless and if, done adding methyl orange it turns yellow from orange.), ˆ Electrolysis of aqueous solution of copper sulphate (CuSO4) using active electrodes of copper (Cu), If electrolysis of aq. solution of CuSO4 is carried out using active electrodes of copper (Cu) then by, overall reaction copper of anode deposits at cathode., 191

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As copper electrode is active electrode it undergo reaction during electrolysis., During electrolysis as the time elapse Cu(s) atoms of copper anode undergo oxidation and produce, Cu2+ ions and goes into the solution. Hence the mass of copper anode decrease as the time elapse. Cu2+, ions present in solution undergo reduction at the surface of cathode and converts into Cu(s) atoms and, deposits at copper cathode. Hence the mass of copper cathode increases., anode (Copper) : Cu(s), , = Cu2+(aq) + 2e-, , Cathode (Copper) : Cu2+(aq), , +, , 2e-, , Overall reaction : Cu(s) (anode), , =, , =, , Cu(s), , Cu(s) (cathode), , In the metallurgy of copper during electrochemical refining impure copper is taken as anode and, when electrolysis is done at proper electrical pressure, impurities of inert metals like Au, Pt present in, anode do not undergo oxidation and they collect at the bottom of the cell. This is called anode-mud., Thus during electrolysis of aq. CuSO4 using active electrodes of copper, no products are obtained, at anode but at the bottom of the cell inert and precious metals like Ag, Au, Pt are obtained in anode mud, and Cu(s) deposits at cathode., When electrolysis of aq. CuSO4 is done using active electrodes of Cu, there is no chage in conc. of, Cu2+ ions and therefore there is no change in blue colour and pH of solution., If electrolysis of aq. CuSO4 is carried out using inert electrodes like graphite or platinum then at, anode O2(g) gas by oxidation of water and copper is obtained at cathode as explained below., At anode : Oxidation of SO24- ions is difficult compared to that of water and hence water is, oxidized and produce H+ ions and O2 gas., At cathode : Reduction of Cu2+ ions present in solution takes place and copper metal is produced., The Cu2+ ions in solution are replaced by H+ ions. Therfore H2SO4 is produced in solution., Thus electrolysis of aq. (CuSO4) using inert electrodes like graphite or platinum gives O2(g) gas at, anode, Cu metal deposits at cathode and H2SO4 is produced in solution., When electrolysis of aq. (CuSO4) is carried out using inert electrodes like graphite or platinum,, acidity of solution increase because H2SO4 is produced in solution and hence pH decreases., (Cu2+ ions present in solution are reduced to Cu(s) and therefore the blue colour of solution fades.), , ˆ Application of electrolysis (OR Importance), (1) It is used in production of metals like Na, Mg, Al production of gases like Cl2, F2 and, production of chemicals like NaOH, KOH etc., (2) Refining of metals like Au, Cu, Pt, Ag is done by electrolysis., (3) Electrolysis is useful in electroplating., 192

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No., , Electrolysis, , Product at anode, , Product at cathode, , 1., , molten NaCl, , Cl2(g), , Na metal, , 2., , Con. aq. NaCl, , Cl2(g), , H2(g) and NaOH, in solution, , 3., , dil. aq. NaCl, , O 2(g), , H 2(g), , 4., , Al2O3 (Na3AlF6) graphite electrodes, , O2(g), F2(g), CO2(g), , Al metal, , 5., , KHF2 in anhydrous HF, , F 2(g), , H 2(g), , ˆ Difference between electrochemical cell and electrolytic cell, Electrochemical cell, , Electrolytic cell, , (1), , Chemical Energy is converted into, electrical energy in this cell., , (1), , Electrical energy is converted into chemi cal energy in this cell., , (2), , Redox reaction is spontaneous and, (DG < 0), , (2), , Readox reaction is not spontaneous and, (DG > 0), , (3), , Generally the two electrodes are in, , (3), , Both the electrodes are dipped in electro, , different containers, , lytic solution or molten electrolyte., , (4), , Anode is (-) and cathode is (+), , (4), , Anode is (+) and cathode is (–). i.e. an, electrode joined with positive terminal of, battery is anode and that joined with negative terminal is cathode, , (5), , Generally salt bridge is required in its, , (5), , Generally salt bridge is not required in its, , construction., (6), , 83., , eg. Daniel cell, , eg. Electrolytic cells used, production of Na, Al, Cl2 etc., , for, , (B) 104600 coulomb, , (C) 25000 coulomb, , (D) 0.26 coulomb, , How many moles of O2(g) and H2(g) would obtain on passing 10 F electricity in electrolysis of water, theoretically ?, (A) 5 mol and 10 mol, , 85., , (6), , The potential of a cell is 2.0 V. If DG for cell reaction is -50 Kcal, then how many coulombs of, electric charge would have been drawn ? (1 cal = 4.184 J), (A) 1.08 coulomb, , 84., , construction., , (B) 10 mol and 5 mol, , (C) 5 mol and 2.5 mol (D) 2.5 mol and 5 mol, , How many grams of Ag would obtain at cathode on passing 5F of electricity from aq. AgNO3, theoretically ? (Ag = 108 gram.mol–1), (A) 270 gram, , (B) 540 gram, , (C) 180 gram, 193, , (D) 135 gram

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86., , How many grams of Al will obtain at cathode experimentally on passing 15.0 F of electricity from Al3+(l)?, (efficiency of cell = 80 %.) (Atomic mass Al, (A) 135 gram, , 87., , (B) 448 litre, , (C) 112 litre, , (D) 62 litre, , (B) 75 %, , (C) 50 %, , (D) 90 %, , (B) pH decrease, , (C) No change in pH, , (D) Cannot be said, , The standard potential of an oxidation of sulphur dioxide into sulphur trioxide in closed container at, 298 K is 0.182 V. The DG0 = -3512.6 J for this reaction. If standard free energy of formation of, SO2(g) is -300.37 KJ mol–1 , then what will be the same for SO3(g)?, (R, , 91., , (D) 94.5 gram, , What will be the change in pH of a solution when aq. CuSO4 is electrolysed using inert electrodes ?, (A) pH increase, , 90., , (C) 108 gram, , At STP, 84 L of Cl2(g) is obtained experimetally on passing 10 F electrical charge in electrolysis of, molten NaCl, then what is the efficinecy of the cell ?, (A) 80 %, , 89., , (B) 121.5 gram, , 27 gram mol–1), , How much litres of O2(g) would obtain theoretically on passing 20 F electricity in electrolysis of water ?, (A) 224 litre, , 88., , =, , =, , 8.314 Jmol–1 K–1, F, , =, , 96500 F mol electron–1), , (A) -313.933 kg joule mol–1, , (B) -235.335 kg joule mol–1, , (C) -296.854 kg joule mol–1, , (D) -335.496 kg joule mol–1, , Reduction of H2O takes place instead of that of Na+(aq) in electrolysis of dil. solution of NaCl using, inert electrodes. Because, ...., (A) Standard reduction potential of Na+(aq) is more than that of H2O., (B) Standard oxidation potential of H2O is very large., (C) inert electrodes are there., (D) Standard potenital of reduction reaction of Na+(aq) is very small., , 92., , What is the proportion of moles at cathodes when same quantity of electricity is passed through, electrolytic cells containing molten NaCl, CaCl2 and AlCl3 joined in a series ?, (A) 1 : 2 : 3, , 93., , (B) 3 : 2 : 1, , (C) 6 : 2 : 3, , (D) 6 : 3 : 2, , Choose correct option for given statements. (T = True statement, F = False statement), (i) The blue colour of solution fades on electrolysis of aq. CuSO4 using active electrodes of Cu., (ii) The pOH of solution increase on electrolysing aq. CuSO4 using inert electrodes., (iii) The solution becomes basic on electrolysing aq. CuSO4 using active electrodes of Cu., (iv) The mass of cathode increase on electrolysing aq. CuSO4 using inert electrodes., (A) FTFT, , 94., , (B) TFFT, , (C) FFTT, , (D) FTTF, , What are the products obtained at cathode and anode respectively on electrolysing a mixture of, KHF2 in anhydrous HF ?, (A) K and F2, , (B) K and H2, , (C) O2 and F2, 194, , (D) H2 and F2

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95., , How many moles of Ca will be obtained at cathode experimentally on passing 5 F electrical charge, through molten CaCl2 ?, (A) 2.5 mol, , 96., , (B) less than 2.5 mol, , What is the ratio of number of moles of metals obtained at different cathodes on passing same, quantity of electricity through electrolytic cells containing CuSO4, AgNO3 and NiSO4 joined in a, series ?, (A) 2 : 1 : 2, , 97., , (B) 2 : 2 : 1, , (C) 1 : 1 : 2, , (D) 1 : 2 : 1, , In an experiment of electroplating ‘m’ gram Ag deposits at cathode on passing 4 ampere electric, current for 2 minutes. How many grams of Ag will deposit if 6 ampere electric current is passed for, 40 seconds ?, (A) 2 m, , 98., , (C) more than 2.5 mol (D) 5 mol, , (B) 4 m, , (C), , m, 2, , (D), , m, 4, , How many faradays of electric charge are required theoretically in order to reduce 1 mole, Cr2O2-7 into Cr3+ ions ?, (A) 6, , 99., , (B) 3, , (C) 1, , (D) 4, , Which relation is true for Faraday’s second law of electrolysis ? Where m1 and m2 are amount of, substances and E1 and E2 are their equivalent weights respectively., (A) m1E2 = m2E1, , (B) m1E1 = m2E2, , (C) m1 + m2 = E2 + E1 (D) E1E2 = m1m2, , 100. Electrolysis of CrCl3 in order to do chromium plating was carried out using 220.0 gram iron plate as, negative electrode by passing 10 ampere electric current for 1221 seconds. The mass of plate increased and became 221.84 gram. What will be the efficiency of this cell ? (At mass : Cr = 52), (A) 90.2 %, , (B) 83.90 %, , (C) 95 %, , (D) 63.89 %, , 101. How much quanitity of electricity in coulombs is required theoretically to reduce 1 mol MnO4- into Mn2+ ?, (A) 96500 C, , (B) 1.93, , ´ 105 C, , (C) 5.62, , ´ 105 C, , (D) 4.83, , ´ 105 C, , 102. How much quantity of electricity is required theoretically in order to reduce all Ag+ in 250 ml of 1.0, M AgNO3 ?, (A) 2412.5 C, , (B) 24125 C, , (C) 4825 C, , (D) 25250 C, , 3+, , 4.5 gram of Al is deposited at cathode, 103. On passing required quantity of electricity through Al(l), experimentally. If same quantity of electricity is passed through solution containing enough concen-, , tration of H+(aq) what volume of hydrogen will be produced at STP ?, (At wt : Al, , = 27 g mol–1), , (A) 44.4 Litre, , (B) 222.4 Litre, , (C) 11.2 Litre, , (D) 5.6 Litre, , 104. By electrolysing CdCl2 using 2g Hg cathode, Cd-Hg amalgam is obtained. How many amperes of, electric current should be passed theoretically for 100 seconds in order to obtain Cd-Hg amalgam, containing 20 % Cd at cathode ? (At mass Cd = 112.5 gmol–1), (A) 34.32 A, , (B) 17.16 A, , (C) 4.29 A, 195, , (D) 8.58 A

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105. On electrolysing unknown salt solution of Pd by passing 5A electric current for 2.15 hours, 10.64, gram Pd is deposited at cathode theoretically. What will be the oxidation state of Pd in that salt ?, (Atomic mass Pd = 106.4 gm mol–1), (A), , +2, , (B), , +3, , (C), , +4, , (D), , +1, , 106. Preparation of MnO2 by electrolysis of aq. solution of MnSO4 is done according to following equation. If 1.0 kg MnO2 is obtained by passing 25A electric current for 30 hours, then what is the, current efficiency ?, (molecular mass MnO2, Mn2+(aq), , = 87 gmol–1), , + H2O(l) ® MnO2(s) + 2H+(aq) + H2(g), , (A) 82.16 %, , (B) 20.54 %, , (C) 25 %, , (D) 49.2 %, , 107. Calculate the experimental mass of metal depositing on cathode when 15 ampere electric current is, passed for 2 hours through electrolytic cell having efficiency 75 %. Electrochemical equivalent of, metal is 4.0 ´ 10–4 gram coulomb–1., (A) 32.4 gram, , (B) 43.2 gram, , (C) 57.6 gram, , (D) 16.2 gram, , 108. The concentration of AgNO3 decrease from 4M to 3M when aq. solution of AgNO3 is electrolysed, using platinum electrodes. If the same solution is electrolysed using Ag electrodes, what result is, obtained ?, (A) the result is same, , (B) concentration of solution increase, , (C) decrease in concentration is less, , (D) no change in concentration of solution, , 109. What will be the theoretical concentration of Ni(NO3)2 solution if 0.5 L of 2.0 M Ni(NO3)2 is electrolysed, by passing 9.65 A electric current for 3 hours using graphite anode and nickel cathode ?, (A) 0.46 M, , (B) 1.46 M, , (C) 0.92 M, , (D) 0.36 M, , 110. What will be the decrease in concentration of Ag+(aq) when 4L of 0.8 M AgNO3 is electrolysed by, passing 5 ampere electric current for 10 hours using inert electrodes ?, (Current efficiency = 80 %), (A) 0.466 M, , (B) 1.865 M, , (C) 1.492 M, , (D) 0.373 M, , 111. How much amperes of electric current should be passed through water in order to produce 100 ml, O 2 per minute at 25°C temperature and 1 bar pressure ? Current efficiency = 90%., R = 0.08314, (A) 23.16 A, , L bar, ), mol K, , (B) 14.35 A, , (C) 28.85 A, , (D) 31.88 M, , 112. In order to obtain 36.47 gram sodium at cathode by electrolysis of molten NaCl for how much time, 10 A electric current should be passed ? Current-efficiency = 85% (At mass Na = 23 gmol–1), (A) 4.25 hr, , (B) 3.6 hr, , (C) 5 hr, , (D) 4 hr, , 113. When 5 L aq. solution of CuSO4 is electrolysed using inert electrodes by passing 25A electric current, the molarity of CuSO4 becomes 1.2 M from 0.7 M, then for how much time electric current, would have been passed theoretically ?, (A) 1.716 hr, , (B) 8.58 hr, , (C) 17.16 hr, 196, , (D) 4.29 hr

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114. When 10 L aq. solution of CuSO4 is electrolysed using inert electrodes by passing electric current for, 20 hours, the molarity of CuSO4 becomes 0.2 M from 0.7 M, then how many amperes of electric, current would have been passed theoretically ?, (A) 13.4 A, , (B) 1.34 A, , (C) 6.7 A, , (D) 26.8 A, , 115. By electrolysing CdCl2using 2 gram Hg cathode, Cd-Hg amalgam is obtained. How many amperes, of electric current should be passed theoretically for 1000 seconds to obtain Cd-Hg amalgam containing 20% Hg ? (At mass : Cd = 112.5 gmol–1), (A) 34.32 A, , (B) 17.16 A, , (C) 4.29 A, , (D) 13.72 A, , 116. To what is Faraday’s law of electrolysis related ?, (A) With atomic number of positive ion, , (B) With atomic number of negative ion, , (C) With speed of positive ion, , (D) With equivalent of electrolyte, , 117. What is the mass deposited at electrode when 1 coulomb electric charge is passed through solution, of electrolyte ?, (A) equal to 1 Chemical equivalent, , (B) equal to 1 atomic mass, , (C) equal to 1 gram, , (D) equal to 1 electro chemical equivalent, , 118. What electric charge will be required in order to deposit 1 equivalent of mass at electrode ?, (A) 1 coulomb, , (B) electric charge on 1 mol e–, , (C) 96500 faraday, , (D) None of the given, , 119. The electrochemical equivalent of a substance is 0.0006735 gram, what will be its chemical equivalent ?, (A) 65 g, , (B) 0.0007635 g, , (C) 34.5 g, , (D) 130 g, , 120. On electrolysing aq. solution of acid 44800 ml O2 is produced at anode, then what will be the volume, of H2 gas produced at cathode during this ?, (A) 11200 ml, , (B) 44800 ml, , (C) 22400 ml, , (D) 89600 ml, , 121. On passing 2A electric current for 2 hours from aq. CuSO4 ‘W’ gram copper deposits at cathode. If, 4A electric current is passed for 4 hours in the same cell what will be the mass of copper deposit at, the cathode ?, (A) 2W gram, , (B), , W, gram, 2, , (C) 4W gram, , (D), , W, gram, 4, , 122. When 9650 electrons are associated with electrolysis, the mass of metal deposited at cathode is 1.2, gram, then what will be the chemical equivalent of metal ?, (A) 24 gm/eq, , (B) 0.12 gm/eq, , (C) 12 gm/eq, , (D) 2.4 gm/eq, , 123. How many amperes of electric current should be passed theoretically in order to collect 112 mL H2, gas at cathode at STP from acidified water in 965 seconds ?, (A) 0.1 A, , (B) 1.0 A, , (C) 0.5 A, , (D) 2.0 A, , 124. In a galvanic cell, in a 1 L of 1.0 M CuSO4 aqueous solution Zn electrode having mass 100 gram is, dipped. If this cell gives 1.0 A electric current continuously, then how long this cell will last ?, (A) 26.8 hr, , (B) 53.61 hr, , (C) 82.48 hr, 197, , (D) 33.78 hr

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125. The surface area of a metalic state is 150 cm2. How long 15 ampere electric current should be, passed from aq. solution of Ag+ in order to coat its surface with 0.01 nm thick layer of Ag ?, (Current efficiency = 90 % ) density of Ag = 10.5 gram cm–3 Atomic mass Ag, (A) 227.979 second, , (B) 205.1811 second, , (C) 253.31 second, , gm, , = 108 mol, , (D) 233.45 second, , 126. For how much time 10 ampere electric current should be passed from aq. solution of Au3+ to coat, metallic bars having dimensions 5 cm ´ 10 cm ´ 2 cm with 0.01 nm thick gold layer ? (Current, efficiency = 80%), density of Au = 19.3 gram cm–3 Atomic mass of Au, (A) 45393.63 second, , (B) 45034.94 second, , = 197, , gram, mol, , (C) 52572.23 second, , (D) 56748.51 second, , 127. For plating on a spoon 0.01 gram silver is consumed. How many spoons will be plated if 0.1A, electric current is passed for 27 hours if electrolyte is aq. solution of AgNO3 ?, (Atomic mass Ag, , = 108 gram mol–1), , (A) 100, , (B) 1088, , (C) 108, , (D) 80, , 128. For how much time 10 ampere electric current should be passed through aq. AgNO3 in order to plate, silver on 1080 spoons ? 0.02 gram silver is being plated on each spoon. (Current efficiency = 90%), (Atomic mass of Ag, (A) 2144 second, , = 108 gram mol–1), (B) 1544 second, , (C) 1930 second, , (D) 2130 second, , 129. When 19,3000 coulomb of electrical charge is passed through electrolytic cell 1 gram atomic weight, of metal deposits on cathode theoretically. What will be the relation between molar mass (M) and, equivalent weight (Eq) of that metal ?, (A) M, , = 2Eq, , (B) M, , = 4Eq, , (C) M, , = Eq, , (D) M, , = 3Eq, , 130. 3.0 mole Ag deposits at cathode theoretically when ‘x’ coulombs of electricity is passed through aq., solution of AgNO3 . How many moles of Al will deposit at cathode theoretically if ‘x’ coulombs of, electricity is passed through aq. solution of Al(NO3)3 ?, (A) 1 mole, , (B) 2 mole, , (C) 9 mole, , (D) 3 mole, , 131. ‘x’ coulombs of electrical charge is passed through aq. solution of Al(NO3)3 . When current efficiency, is 90%, 3 mol Al deposits at cathode experimentally. If ‘x’ coulombs of electrical charge is passed, through aq. solution of AgNO3 and current efficiency is 80%, then how many moles of Ag will, deposit at cathode experimentally ?, (A) 7.2 mol, , (B) 10 mol, , (C) 8 mol, , (D) 8.5 mol, , Answers : 83. (B) 84. (D) 85. (B) 86. (C) 87. (C) 88. (B) 89. (B), 90. (D), 91., 92. (D), 93. (A), 94. (D), 95. (B), 96. (D), 97. (C), 98. (A), 99. (A), 100., 101. (D), 102. (B), 103. (D), 104. (D), 105. (C), 106. (A), 107. (A), 108., 109. (C), 110. (D), 111. (C), 112. (C), 113. (B), 114. (A), 115. (D), 116., 117. (D), 118. (B), 119. (A), 120. (D) 121. (A), 122. (C), 123. (A), 124., 125. (C), 126. (D), 127. (B), 128. (A), 129. (A), 130. (A), 131. (C), 198, , (D),, (B),, (D),, (D),, (B),

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ˆ Electrical resistance, The resistance of a uniform conductor is directly proportional to its lenght (l) and inverssely, proportional to its area of cross section (A)., Electric resistance is expressed by R. Its unit is ohm (W). It is measured by wheatstone bridge., l, where, R, A, , \, , R, , µ, , \, , R, , = r, , =, , ( Al ) where,, , resistance, l, , r =, , =, , length, A, , =, , area of cross section, , resistivity (specific resistance) and its SI unit is (Wm). Generally it is, , expressed by (Wcm)., Resistivity (Specific resistance) : The resistance of a conductor having 1 m length and 1m2 cross, section of area is called resistivity or specific resistance., SI unit of resistivity is ohm metre (Wm). It is generally expressed ohm cm (Wcm)., 1, , m, , W, , =, , 100, , cm, , W, , Conductivity : The inverse of resistance is called conductivity., G=, , \, , 1, R, , G, , =, , \, , K, , (l), , A, , G = . (QR = r A ), ρl, ., , A, where K, l, , =, , 1, ρ, , =, , specific conductivity, , The SI unit of conductance is Siemens (S). It is generally expressed as ohm–1 or ohm W–1 or mho, , )., , Specific conductivity (k) : The conductance of a conductor having length equal to 1m and area, of cross section equal to 1m2 is called its specific conductivity or simply conductivity. It is the inverse of, resistivity (r)., \, , K, , =, , 1, and, ρ, , r =, , R .A, l, , Unit of K : mho.cm–1 (, , \, , K, , =, , 1, R .A, , cm–1) SI unit = Sm–1., , Cell constant (G*) : The term, , l, in the formula of specific conductivity is known as cell constant, A, , G*. Unit of cell constant (G*) : cm–1, SI unit is m–1., The conduction of electricity in metallic conductors is done by electrons present in outermost shell or, conduction band of metal atoms., The conduction of electricity in electrolytic solutions is by ions., In metals there is no chemical change during the conduction of electricity., The temperature of metals increase during conduction of electricity., Molar conductivity ( / m) : The conductance of a solution kept between two electrodes at a distance, of unit length with unit area of cross section containing 1 mole of electrolyte is called molar conductivity., Suppose V litre of solution placed between two electrodes contain 1 mole electrolyte, therefore, molarity of solution M, , =, , 1, therefore V, V, , =, , 1, M, , ., , 199

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G, \, , Λm = k, , l, , =, , 1 cm and A, , =, , V and G, , =, , k, , ., , V, where according to definition, G, , =, , Λm, , V, , Λm =, , \, , 1 mol, , ., , A, , where, l, , ., , k, , =, , k, (If molarity of solution is M, then M mol, M, , =, , 1 L solution. Therefore solution will be, , 1, litre.), M, , M, , =, , Λm =, , mol, L, k, M, , M mol, =, , =, , dm, , M mol, =, , 3, , k, M mol, 1000 cm, , 1 Sm2 mol–1, , =, , 1000 cm, , 3, , 1 0 0 0 cm, , =, , × k mho cm −1, M mo l, 3, , =, , 1000 × k, mho.(cm)2 mol–1 or S(cm)2 mol–1, M, , 3, , 104 S cm2 mol–1, , Equivalent conductivity ( Λ ), , =, , 1000 × k, 2, –1, 2, –1, Normality (N) Unit : mho (cm) eq , SI unit : S (cm) eq, , When aq. solution of any electrolyte is diluted by adding water into it the number of ions conducting, electric current per unit volume decrease and hence specific conductance decrease. But due to dilution,, dissociation of electrolyte increase and therefore the number of ions conducting electric current per mole, increase and hence molar conductivity increases., Super Conductors : The substances having zero resistivity or infinite conductivity are called super, conductors., Earlier metals and alloys at a temperature (0 to 15 K) were known to behave as super conductors,, but now a days a number of ceramic materials and mixed oxides are also known to show super conductivity, at temperatures as high as 150 K., The conductivity of solutions is mainly due to the presence of ions in them. It is called ionic conductivity., Factors affecting ionic conductivity are :, (1) Nature of electrolyte added (2) Concentration of electrolyte (3) temperature (4) viscosity, (5) Nature of solvent (6) size of the ions produced and their solvation., 132. Which is the correct order of specific conductance of the metals given ?, (A) Cu, , >, , Ag, , >, , Au, , >, , Na, , >, , (C) Ag, , >, , Cu, , >, , Au, , >, , Na, , >, , Fe, , (B) Ag, , >, , Cu, , >, , Au, , >, , Fe, , >, , Na, , Fe, , (D) Ag, , >, , Au, , >, , Cu, , >, , Fe, , >, , Na, , 133. The resistance of aq. solution of KCl having conductivity “x” mho cm–1 at definite temperature is, y, , W, , . If resistance of aq. solution of NaCl measured with the same instrument is “z”, , W, , then what, , is the conductivity of this solution ?, (A), , yz, mho (cm)–1, x, , (B), , xz, , xy, mho (cm)–1, z, , (C) y mho (cm)–1, 200, , x, , (D) yz mho (cm)–1

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134. The electrical resistance and conductivity (k) of 0.2 M aq. solution of an electrolyte are 50 W and, 1.3 Sm–1 respectively. If electrical resistance of 0.4 M aq solution of same electrolyte is 260 W, then, what will be its molar conductivity ?, (A) 6.25, , ´, , 10–4 Sm2 mol–1, , (B) 625 Sm2 mol–1 (C) 62.5 Sm2 mol–1, , 135. The electrical resistance and specific conductivity of a cell containing, , (D) 6.25, , ´, , 10–2 Sm2 mol–1, , N, KCl solution are 400, 50, , W, , and 0.002765 S cm–1, then what will be the value of its cell constant ?, (A) 6.91 cm–1, , (B) 1.106 cm–1, , (C) 14.46 cm–1, , 136. If conductivity and electrical resistance of a conductivity cell containing, 1.12, , (D) 2.212 cm–1, N, KCl solution at 18°C are, 10, , ´ 10–2 S cm–1 and 65 W respectively then what will be the value of cell constant of this cell ?, , (A) 0.728 cm–1, , (B) 0.580 cm–1, , (C) 0.172 cm–1, , (D) 0.0172 cm–1, , 137. What will be the quantity of electricity passed when a potential difference of 20 V is applied to a, wire having resistance 10 W for 2 minutes ?, (A) 120 C, , (B) 240 C, , (C) 20 C, , (D) 4 C, , (C) 0.025, , (D) 0.25, , 138. 2.5 Sm–1 = .......... Scm–1, (A) 250, , (B) 25, , 139. According to conventional symbol system, , (A), , r, , l, AR, , = .......... ., , (B) K.G, , (C) G, , 1, , (D) ρ, , 140. At what temperature metals and alloys were termed as super conductors earlier ?, (A) 150 K, , (B), , -273o C to -288o C, , (C) 0o C to15o C, , (D) 0 K to 15 K, , 141. Which substances are known as super conductors at 150 K temperature ?, (A) metals, , (B) alloys, , (C) ceramic materials and mixed oxides, , (D) plastic, , 142. Whose conductivity is most at room temperature ?, (A) 0.1M HCl, , (B) 0.1M NaCl, , (C) Teflon, , (D) glass, , (C) Glass, , (D) Cu2O, , 143. Which substance is semi conductor ?, (A) Teflon, , (B) CuO, , Answers : 132. (C) 133. (B) 134. (A) 135. (B) 136. (B) 137. (B), 138. (C), 139. (D),, 140. (D), 141. (C), 142. (A), 143. (B), Kohlrausch law of independent migration of ions : The molar conductivity (/ 0) of an elec-, , trolyte at infinite dilution is equal to the sum of molar conductivities of its cation and anion (l0+, and l0-) at infinite dilution., 201

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ˆ Debye Huckel and Onsager equation for molar conductivity of aqueous solution of electrolyte, Λ m = Λ 0m - A . C where, Λ m = molar conductivity of given solution, Λ 0m = Limiting molar conductivity, , For aq. solution of strong electrolytes the graph of Λ m ®, , C is straight line. The value of slope is, , equal to -A and the intercept of Y-axis is equal to Λ 0m., The value of A depends on type of electrolyte, solvent and temperature., The value of A for same type of electrolytes is same (when solvent and temperature are same), For aq. solutions of weak electrolytes the graph of Λ m ®, , C is not a straight line but curve., , C , molar conductivity ( Λ 0m) at infinite dilution of aqueous solutions, , Therefore, from the graph of Λ m ®, , of strong electrolytes can be determined but the same for aqueous solutions of weak electrolytes cannot be, determined., KCl, NaCl, CsCl ... etc are 1 : 1 type of, CuSO4, ZnSO4, FeSO4 ..... etc. are 1:2 type of, electrolytes., , graph of weak, electrolyte, eg. CH3COOH, , 300, , CaCl2, MgBr2, .........etc. are 2 : 1 type of, electrolytes. (Based an valency), , graph of strong, electrolyte eg. KCl), , 200, , Ostwald’s law of dilution : The increase in, molar conductivity of aq. solution of weak, , 100, , electrolytes is specifically more when diluted by, , mol-1), , molar conductivity mho cm2, , electrolytes., , adding water compared to that for strong, 0.1, , 0.2, , 0.3, , electrolytes. Because, the increase in dissociation is, , 0.4, , specifically more in aq. solution of weak electrolytes, , CM1/2, , when diluted by water than that in strong, electrolytes., , Application of Kohlrausch law : Molar conductivity ( Λ 0) of weak electrolytes can be, obtained from molar conductivities of strong electrolytes at infinite dilution by doing algebraic addition., For example, molar conductivity of weak electrolyte like CH3COOH can be obtained from molar, conductivities at infinite dilution of strong electrolytes like CH3COONa, HCl and NaCl., Λ 0CH, , 3COOH, , Λ 0CH COONa, 3, , =, , +, , Λ 0CH, , 3COONa, , Λ 0HCl, , -, , +, , Λ 0HCl - Λ 0NaCl because according to the kohlraush law,, , Λ 0NaCl, , =, , (l0CH, , = l, , 0, , =, , 0, , l, , 3COO, , CH3COO, , +, , +, , CH3COO, , +, , +, , +, , +, , 202, , l, , l, , 0, Na, , 0, , l, , Na, 0, H, , +, , +, , +, , ), , +, , ( l 0H, 0, , +, , l, , =, , Λ 0CH, , H, , +, , +, , +, , +, , l, , 3COOH, , l, , 0, Cl, , 0, Cl, , -, , -, , ), , -, , -, , l, , (l0Na, , +, , 0, Na, , +, , +, , + l, , 0, Cl, , l, , -, , 0, Cl, , -, , )

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= 106 S cm 2mol –1, Λ 0m C a2 = 119 S cm 2mol –1, Λ 0mCl = 76.3 S cm 2mol –1,, Λ 0mSO42– = 160 S cm2mol–1 Choose correct option for compound given in group-I and molar con-, , 144. Λ 0 m M g 2, , +, , +, , -, , ductivity at infinite dilution in Group II., Group-I compound Group-2 / 0m S cm2 mol–1, (i) MgSO4, , (A) 195.3, , (E) 182.3, , (A) (i)-(C), (ii)-(D), (iii)-(H), (iv)-(B), , (ii) CaCl2, , (B) 279, , (F) 266, , (B) (i)-(F), (ii)-(A), (iii)-(E), (iv)-(G), , (iii) MgCl2, , (C) 186, , (G) 219.5, , (C) (i)-(F), (ii)-(D), (iii)-(H), (iv)-(B), , (iv) CaSO4, , (D) 271.6, , (H) 258.6, , (D) (i)-(C), (ii)-(G), (iii)-(A), (iv)-(E), , 145. 1 Λ 0 m A 1 3, 3, , +, , = 63 S cm 2mol –1,, , 1 0, Λ mMg2+, 2, , = 53 S cm 2mol –1, Λ 0m OH = 199.1 S cm 2mol –1,, -, , 1 0, Λ SO 3– = 80 S cm2mol–1 Choose correct option for compound given in Group-I and molar conduc2 m 4, , tivity at infinite dilution in Group-II., Group-2 / 0m S cm2 mol–1, , Group-1 Compound, (i) MgSO4, , (A) 504.2, , (E) 786.3, , (A) (i)-(C), (ii)-(D), (iii)-(H), (iv)-(B), , (ii) Al2(SO4)3, , (B) 133, , (F) 451.2, , (B) (i)-(F), (ii)-(A), (iii)-(E), (iv)-(G), , (iii) Mg(OH)2, , (C) 266, , (G) 858, , (C) (i)-(F), (ii)-(D), (iii)-(H), (iv)-(B), , (iv) Al(HO)3, , (D) 660.3, , (H) 366, , (D) (i)-(C), (ii)-(G), (iii)-(A), (iv)-(E), 1, , 146. For which of the given compound the graph of molar conductivity and (molarity) 2 is straight line ?, (A) CsCl, , (B) NH4OH, , (C) HCOOH, , (D) All three given, , 1, , 147. To which compound Λ m = Λ 0m - A.C 2 is applicable ?, (A) NaCl, , (B) NH4OH, , (C) HCOOH, , (D) HCN, , 148. Whose equivalent conductivity at infinite dilution is most ?, (A) K+(aq), , (B) Na+(aq), , (C) Cs+(aq), , (D) Rb+(aq), , 149. For a strong electrolyte when C = 0.04 M, Λ m = 250 S cm2mol–1 and when C = 0.09 M then, Λ m = 200 S cm2mol–1 then what will be Λ and Λ m0 respectively for this electrolyte ?, (A) 550, 265 S cm2mol–1, , (B) 450, 365 S cm2mol–1, , (C) 500, 350 S cm2mol–1, , (D) 340, 450 S cm2mol–1, 203

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158. The molar conductivity at infinite dilution of a weak acid having concentration 0.01 M is 100 times, the molar conductivity. What will be the degree of dissociation (a) of this acid ?, (A) 0.1, , (B) 0.001, , 159. If Λ 0m of Ag, , +, , (C) 10, , = 5.0 ´ 10–3 S cm2 mol–1 then what will be the ionic mobility of Ag at infinite dilution ?, +, , −1, , (A) 5.2, , (D) 0.01, , −1, , ´ 10–8 cm.sec− 1, , (B) 2.4, , V.cm, , ´ 10–8 cm.sec− 1, V.cm, , −1, , −1, , ´ 10–8 cm.sec− 1, , (C) 1.52, , (D) 8.25, , V.cm, , 160. If Λ 0ClCH, , 2COONa, , ´ 10–8 cm.sec− 1, V.cm, , = 224 S cm2 mol–1, Λ 0NaCl = 38.2 S cm2 mol–1 and Λ 0HCl = 203 S cm2 mol–1 then, , what will be the value of Λ 0ClCH, , 2COOH, , ?, , (A) 288.5 S cm2 g eq–1, , (B) 289.5 S cm2 g eq–1, , (C) 388.8 S cm2 g eq–1, , (D) 59.5 S cm2 g eq–1, , 161. The ionization constant of a weak electrolyte is 2.5 ´ 10–5 at 298 K and molar conductivity of its, 0.01 M solution is 19.6 S cm2 mol–1. What will be its approximate molar conductivity at infinite, dilution ?, (A) 250 S cm2 mol–1, , (B) 196 S cm2 mol–1, , (C) 402 S cm2 mol–1, , (D) 384 S cm2 mol–1, , 162. Specific conductivity of 0.001028 M acetic acid at 300 K is 4.95 ´ 10 –5 S cm 2 mol –1, and its limiting molar conductivity is 390 S cm2 mol–1, then what will be its dissociation constant ?, (A) 1.75, , ´ 10–6 M, , (B) 1.78, , ´ 10–5 M, , (C) 3.5, , ´ 10–4 M, , 163. The equivalent condutivity at infinite dilution of aq HCl at 298 K is 425, tivity is 3.825, , (D) 3.5, Scm, Eq, , ´ 10–6 M, , 2, , and its specific conduc-, , S, . If HCl is 90% dissociated, then what will be the normality of HCl ?, cm, , (A) 10.0 N, , (B) 1.0 N, , (C) 1.2 N, , (D) 0.9 N, , 164. What is the change in specific conductivity and molar conductivity respectively of aq. solution of, electrolyte when diluted by water ?, (A) Both increase, , (B) Both decrease, , (C) decreases and increases., , (D) increases and decreases., , 165. The molar conductivity of aq. solution of electrolyte at definite temperature increases by increasing, its volume adding water. Because, ......, (A) number of ions decrease., , (B) degree of dissociation of electrolyte decrease., , (C) distance between the ions increase., , (D) number of ions conducting current increases., , 166. If molar conductivity of a given solution is 1.26, what will be its specific conductivity ?, , ´ 10–25 S cm2 mol–1, (C) 1.26 ´ 10–4 S cm2 mol–1, (A) 1.26, , ´ 10–4 S cm2 mol–1 and molarity is 0.01 M then, (B) 1.26, , ´ 10–5 S cm2 mol–1, , (D) 0.00063 S cm2 mol–1, 205

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167. If 0.1 M KCl solution is added into aqeous soltution of 0.1 M NaCl, then molar conductivity of, solution ......, (A) remains constant., , (B) increases., , (C) decreases., , (D) increases initially and then decreases., 2, , 168. If molar conductivity of aq. solution of sulphuric acid at definite temperature is 150, , Scm, mol, , then what, , will be its equivalent conductivity ?, Scm, Eq, , (A) 75, , 2, , (B) 150, , Scm, Eq, , 2, , (C) 300, , Scm, Eq, , 2, , (D) none of the given, , 169. Equivalent conductivity of NaCl at concentration ‘C’ and infinite dilution are, Which of the following relation for, , l, , C, , lC and l¥ respectively., , and l¥ is true ? (where constant B is positive), , lC = l¥ + (B)C (D) lC = l¥ - (B) C, 170. The resistance of a 0.2 M electrolytic solution is 50 W. The specific conductivity of solution is 1.4, (A), , lC = l¥ + (B), , C (B), , lC = l¥ + (B)C, , (C), , Sm–1. The resistance of the 0.5 M solution of same electrolyte is 280, molar conductivity of 0.5 M solution of that electrolyte ?, (A) 5, , ´ 10, , 2, , (B) 5, , ´ 10, , –4, , (C) 5, , ´ 10, , –3, , W. Then what will be the, (D) 5, , ´ 10, , 3, , 171. If molar conductivities of AgNO3, AgCl and NaCl at infinite dilution are 116.5, 121.6 and 110.3, 2, , Scm, mol, , then what will be the molar conductivity of NaNO3 at infinite dilution ?, , (A) 105.2, , Scm 2, mol, , (B) 130.6, , Scm 2, mol, , (C) 111.4, , 172. The molar conductivity of 0.1 N CH3COOH at 398 K is 80, infinite dilution is 400, (A) 0.1, Answers : 132., 140., 148., 156., 164., 172., , (D) 150.2, , Scm 2, mol, , Scm 2, . White its molar conductivity at, mol, , Scm 2, . Then what will be the degree of dissociation of solution of CH3COOH ?, mol, , (B) 0.5, (C), (D),, (C),, (D),, (C),, (C), , Scm 2, mol, , 133., 141., 149., 157., 165., , (B), (C),, (C),, (C),, (D),, , (C) 0.2, 134., 142., 150., 158., 166., , (A), (A),, (C),, (D),, (B),, , 135., 143., 151., 159., 167., , (B) 136., (B), 144., (A), 152., (A), 160., (B), 168., , (D) 0.4, (B) 137. (B),, (C), 145. (D),, (B), 153. (B),, (C), 161. (C),, (C), 169. (D),, , 138., 146., 154., 162., 170., , (C),, (A),, (B),, (D),, (B),, , 139., 147., 155., 163., 171., , (D),, (A),, (A),, (A),, (A),, , Primary cells : Those cells which become dead after a long use and cannot be recharged are, called primary cells. Eg. dry cell., Secondary cells : Those cells which become dead after a long use but can be recharged are called, secondary cells. eg. Lead storage cell, Ni-Cd storage cell., 206

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ˆ Dry cell (Lenclanche cell), anode : Zn(s), , = Zn2 + 2e-, , cathode : 2MnO2, , + 2NH4+ + 2e- = Mn2O3 + 2NH3 + H2O, , The manganesge containing product obtained at, cathode depends on the continuous use of cell and, Seal, , duration between two successive use of the cell., , Graphite Cathod, , Mn(III) cannot be oxidized into Mn(IV) by, reversing the direction of current and hence this cell, cannot be recharged once it becomes dead., , MnO2 + C, Paste of, , Dry cell is not dry in reality because it consists, , NN4Cl + ZnCl2, , of moist paste of NH4Cl and ZnCl2. If it is completely dry then it cannot conduct electric current., , Zinc anode, , The potential of this is 1.5 V., Uses : It is used in torch, transistor, radio and other small and large instruments., ˆ Lead storage cell, Anode, Pb, , Cathode, PbO 2, , When both the electrodes are connected with conducting wire, electric current is produced by following, reactions., (Discharging reactions), Anode : Pb(s) + SO24-(aq), , 30 % W/W, H2SO4, , Cathode : PbO2(s), PbSO4(s) + 2H2O(l), , = PbSO4(s) + 2e-, , + 4H+(aq) + SO24-(aq) + 2e- =, , The potential of this cell is 2.0 V., When this cell is working H2SO4 is consumed and water is produced therefore density of, H2SO4 decreases. Initial density is 1.25 - 1.30 gmL–1 and when the cell stops working it beocmes, 1.10 - 1.15 gmL–1., The charging reactions occuring at electrodes are as follows :, Anode : PbSO4(s) + 2H2O(l), Cathode : PbSO4(s) + 2e-, , = PbO2(s) + 4H+(aq) + SO24-(aq) + 2e-, , anode, , cathode, , = Pb(s) + SO24-(aq), , ˆ Mercury Cell, anode : Zinc-mercury (Zn-Hg) layer, cathode : Mercury oxide (HgO) and carbon, Electrolytes : KOH and ZnO paste, , gasket, 207, , separator cathode, , container

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ˆ Electrode reactions, anode : Zn(Hg) + 2OHcathode : HgO + H2O(l), , ®, , ZnO(s), , + 2e-, , ®, , overall reaction : Zn(Hg) + HgO, , + H2O(l) + 2eHg(l), , ®, , + 2OH-, , ZnO(s), , +, , Hg(l), , cell potential : 1.35 V, No ions are produced during overall reaction in this cell., ˆ Nickel-Cadmium (Ni-Cd) storage cell, The life of this cell is more than that of lead stroage cell but its production cost is high., Discharging reaction of the cell : Cd(s), , + 2Ni(OH)3(s) ® CdO(s) + 2Ni(OH)2(s) + H2O(l), , The potential of cell is 1.2 V., ˆ Hydrogen fuel cell, , water, , Hydrogen fuel cell : Hydrogen gas is used as, , anode, , cathode, , fuel in this cell., Concentrated aq., solution, of NaOH, , Construction : In a container between two, membranes of porous carbon containing catalyst concentrated aq. NaOH solution is filled., These membranes work as electrodes., , H2, , O2, , Platinum is used as catalyst in anode and, mixed powder of platinum and silver oxide is used as, catalyst in cathode., anode : 2H2(g), cathode : O2(g), , + 4OH-(aq) = 4H2O(l) + 4e+ 2H2O(l) + 4e- = 4OH-(aq), , The potential of cell is 1.23 V., Theoretically current efficiency of this cell is expected to be 100% but in reality it is 70-75%., Efficiency of fuel cell, , =, , ∆G, ∆H, , ´, , 100 %, , Advantages of fuel cell : Compared to other cells, fuel cell has many advantages., It does not create air pollution., It does not create noise pollution., Its current producing efficiency is very high compared to that of thermal power stations., American scientists used this type of cell in Apollo space programme. In addition, the, vapour of water produced during reaction was cooled and was used for drinking purpose., Limitation : It works at very high temperature., Corrosion : A salt is produced on the surface of metal by a redox reaction between metal and, oxygen present in air on the surface of metal. This reaction is called corrosion., 208

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The actual reactions of corrosion are complex. The rusting of iron can be explained as follows :, air rust, (Fe2O3), , O2, , cathode, O2, , Fe2+ water, e-, , + 4H+ + 4e- = 2H2O, , anode, Fe = Fe2+, , + 2e-, , Iron, The iron atoms present at the bent surface of metal undergo oxidation., anode : Fe(s) = Fe2+(aq), , + 2e- (oxidation), , The water required for this reaction is available from moist air., The oxygen present in air undergo reduction in presence of H+. This point acts as cathode., Cathode : O2(g), , + 4H+(aq) + 4e- = 2H2O(l)(reduction), , The H+ ions required for the reduction are obtained by decomposition of H2CO3 formed on, surface of metal by dissolution of CO2 in moisture., The Fe2+(aq) produced by oxidation are further oxidized into Fe3+ by oxygen of air and diffuse, towards cathode and eventually rust Fe2O3. xH2O is formed., If H+ are not available as cathode then oxygen gas dissolved in moisture is reduced, O2(aq), , + 2H2O(l) + 4e- = 4OH-(aq), , ˆ Methods of preventing corrosion, One of the methods to prevent iron from rusting is that moisture should not be allowed to, come in contact with it, so that oxidation reaction does not occur., The most easiest method for this is applying paint on the surface of iron. But it does not last, for long time and as the paint is removed rusting starts., Iron does not rust if a thin layer of Zn is applied on it. Such iron coated with layer of Zn is, called galvanised iron and this process is called galvanizing., If a little layer of Zn is peeled off even then iron does not get rusted. Because E0Zn/Zn2+ is, greater than E0Fe/Fe2+., If a layer of tin (Sn) is applied on iron and a little layer of tin is peeled off rusting of iron, takes place. Because E0Fe/Fe2+ is greater than E0Sn/Sn2+., In another method of preventing rusting of iron, it is connected with metals like Mg or Zn, having high E0OX and metal is burried under the earth., In order to prevent corrosion of the iron plates of steamer they are connected with large, blocks of Mg or Zn and kept in contact with water. By doing so, iron plates act as cathode and Mg, or Zn blocks act as anode. Thus blocks get corroded and hence to be replaced periodically., Therefore Mg and Zn blocks are called sacrificial anodes., In addition to this, some chemicals called inhibitors are used. By using them they combine with, metal surface by chemical bonds and prevents corrosion., 209

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173. Which of the following cell cannot be recharged once it is dead ?, (A) Lead storage cell, , (B) Ni-Cd storage cell (C) Leclanche cell, , (D) All three given, , 174. Which is the charging reaction occuring at anode in Lead storage cell ?, (A) PbSO4(s), , +, + 2H2O(l) ® PbO2(s) + SO24-(aq) + 4H(aq), + 2e-, , (B) PbSO4(s), , ® Pb(s) + SO24-(aq) 2e-, , (C) Pb(s), , + SO24-(aq), , (D) PbSO4(s), , ® PbSO, , 4(s), , + 2e-, , + 2H2O(l) ® Pb2(s) + SO24-(aq) + 4H+(aq) + 2e-, , 175. The reaction occuring in hydrogen fuel cell is 4H2(g), (A) 571.7 KJ, , (B) 1503.4 KJ, , + 2O2(g) ® 4H2O(l) . Give the value of DHrea., , (C) 157.5 KJ, , (D) 1143.4 KJ, , 176. Which catalysts are used in fuel cell at anode and cathode respectively ?, (A) Ag2O and Pt, , (B) Pt and Pt + Ag2O mixed powder, , (C) Pt and Ag2O mixed powder, , (D) graphite and Pt, , 177. From the options given below which cell has different principle ?, (A) Daniel cell, , (B) Lead storage cell, , (C) Leclanche cell, , (D) Electrolytic cell, , 178. From the research of which scientist on urea a separate branch of organic chemistry was evolved ?, (A) Wohler, , (B) Faraday, , (C) Nernst, , (D) Raoult, , 179. What is the change in E0cell on multiplying the electrode reactions occuring in electrochemical cell by n ?, (A) no change., , (B) becomes n times., , (C) becomes 1/n times. (D) becomes 2n times., , 180. In Group-1 cells and in Group-2 potentials are given. Choose the correct option for that :, Group-1, , Group-2, , (i) Leclanche cell, , (A) 1.23 V, , (E) 1.32 V, , (A) (i)-(C), (ii)-(D), (iii)-(F), (iv)-(A), , (ii) Lead storage cell, , (B) 2.35 V, , (F) 1.35 V, , (B) (i)-(H), (ii)-(D), (iii)-(B), (iv)-(G), , (iii) Mercury cell, , (C) 1.53 V, , (G) 1.75 V, , (C) (i)-(E), (ii)-(D), (iii)-(F), (iv)-(A), , (iv) Fuel cell, , (D) 2.0 V, , (H) 1.5 V, , (D) (i)-(H), (ii)-(D), (iii)-(F), (iv)-(A), , 181. What is present as electrolyte in mercury cell ?, (A) Paste of NH4Cl and ZnCl2, , (B) Paste of KOH and HgO, , (C) Paste of KOH and ZnO, , (D) HgO and graphite, , 182. The dissociation constant of a weak acid is 1.77 ´ 10–5. Its Λ 0m is 390.5 S cm2 mol–1, then what will, be the molar conductivity of its 0.01 M aqueous solution ?, (A) 4.53 S cm2 mol–1, , (B) 16.78 S cm2 mol–1 (C) 45.3 S cm2 mol–1, 210, , (D) 164.3 S cm2 mol–1

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183. What is the efficiency of hydrogen fuel cell ?, (A) 35 %, , (B) 100 %, , (C) 70 to 75 %, , (D) 50 to 60 %, , 184. The blocks of which metals are used as sacrificial anodes to prevent rusting of iron plates of steamer ?, (A) Sn and Mg, , (B) Zn and Co, , (C) Ni and Cu, , (D) Zn and Mg, , 185. Which of the given metal is beneficial for electroplating of iron in order to prevent it from rusting ?, (A) Sn, , (B) Ni, , (C) Cu, , (D) Zn, , 186. The Eox of Cr | Cr3+ and Zn | Zn2+ are 0.74 V and 0.76 V respectively. Which statements are true, for reaction given below ? 2Cr3+(aq.0.001M), , + 3Zn(s), , U 2Cr, (s), , + 3Zn2+(aq.0.1M) T = 298 K, , (1) The rate of forward reaction is more than that of reverse reaction., (2) Forward reaction takes place but reverse reaction does not take place., (3) Both forward and reverse reactions take place., (4) The rate of reverse reaction is more than that of forward reaction., (5) Both forward and reverse reaction occurs at same rate., (A) (1), (3), , (B) (2), , (C) (5), , (D) (3), (4), , 187. Standard reduction potentials at 25o C are given as follows :, E0Fe3+|Fe2+, E0Cr3+|Cr, O2(g), , +, , = 0.77 volt, E0Fe2+|Fe, , = -, , 0.74 volt, E0Cr2+|Cr, , = -, , = -, , + 2H2O, , +, , 4e, , -, , ® 4H, , -, , E0, , 0.44 volt, E0Cu2+|Cu, , = +, , 0.91 volt, O2(g), , 4H, , = +, , +, , +, , 0.34 volt, E0Cu+|Cu, , +, , +, , -, , 4e, , ®, , = +, , 2H2O E0, , 0.52 volt,, 1.23 volt,, , = +, , 0.40 volt., , For the redox couples given in column-I, potentials are given in column-II, if column-I is correctly, matched with column-II, then which option is true ?, Column-I, (P) E0Fe3+|Fe, (Q) 4H2O, (R) Cu2+, , ® 4H+ + 4OH-, , + Cu ® 2Cu+, , (S) E0Cr3+|Cr2+, , Column-II, , P, , Q, , R, , S, , (1) -0.18 volt, , (A), , 4, , 1, , 2, , 3, , (2) -0.40 volt, , (B), , 2, , 3, , 4, , 1, , (3) -0.04 volt, , (C), , 1, , 2, , 3, , 4, , (4) -0.83 volt, , (D), , 3, , 4, , 1, , 2, , 188. Choose correct option for given statements. (T = True statement, F = false statement), (i) Due to conduction of current the temperature of metal increases and the composition of aqueous solution of electrolyte does not change., (ii) Due to conduction of current metal undergo chemical reaction and the composition of aqueous, solution of electrolyte changes., (iii) Due to conduction of current there is no change in composition of metal and aqueous solution of, electrolyte., (iv) Due to conduction of current the temperature of metal increase and the composition of aqueous, solution of electrolyte changes., (A) FFFT, (B) TFTF, (C) TTFF, (D) FFTF, 211

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193. In column-I the substance electrolysed and in column-II and column-III the products obtained at, anode and cathode respectively are given, then match them properly :, Column-1, , Column-2, , Column-3, , (1) NaCl (molten), , (A) O2(g), , (P) Al metal, , (2) NaCl (Conc..aq.), , (B) O2(g), CO2(g), , (Q) Cl2, , (3) NaCl (dil. aq.), , (C) Cl2(g), , (R) Na metal, , (4) Al2O3 (Na3AlF6), , (D) F2(g), , (S) H2(g) and NaOH in solution, , (5) KHF2 anhyd HF, , (E) H2(g), , (T) H2(g), , (A) (1)-(C)-(R), (2)-(C)-(T), (3)-(A)-(T), (4)-(B)-(P), (5)-(D)-(T), (B) (1)-(C)-(R), (2)-(C)-(S), (3)-(A)-(T), (4)-(B)-(P), (5)-(D)-(T), (C) (1)-(C)-(R), (2)-(C)-(S), (3)-(A)-(Q), (4)-(B)-(P), (5)-(D)-(T), (D) (1)-(C)-(R), (2)-(C)-(S), (3)-(C)-(T), (4)-(B)-(P), (5)-(D)-(T), 194. The cell potential at 298 K temperature for Pt | H2(g.1.0 bar) | OH-(aq.0.02M) || H+(aq) | H2(g.1.0 bar) | Pt is, 0.61V, then what will be the pH of solution of half-cell at R.H.S. ? The ionic product of water, (KW) at 298K is 1.02, (A) 1.95, , ´ 10–14., (B) 12.05, , (C) 3.15, , (D) 2.5, , 195. Choose the correct option for given statements with reference to electrochemical cell :, Zn(s) | Zn2+(aq.0.02M) || Cu2+(aq.0.05M) | Cu(s)., Assertion(A) : Ecell increase on increasing concentration of Zn2+(aq), Reason, , (R) : EOX of anode increase on increasing concentration of Zn2+(aq)., , (A) Assertion (A) and reason (R) both are correct and (R) is reason of (A)., (B) Assertion (A) and reason (R) both are correct but (R) is not the reason of (A)., (C) Both assertion (A) and reason (R) are wrong., (D) Assertion (A) is wrong and reason (R) is correct., 196. Two statements are given in every question given below. One is assertion (A) and another is, reason (R). Study the statements carefully and choose proper option as per given instruction., Assertion (A) : The oxygen gas is libertated at anode on electrolysing aq. Na2SO4 using pt, electrodes., Reason (R), , : 2SO42-(aq) U S2O82-(aq), 2H2O(l) U O2(g), , + 2e-, , + 4H+(aq) + 4e-, , (i), (ii), , The standard potential of (ii) is more than that of (i), (A) Assertion (A) and reason (R) both are correct and R is the reason of (A), (B) Assertion (A) and reason (R) both are correct but (R) is not the reason of (A)., (C) Both assertion (A) and reason (R) are wrong., (D) Assertion (A) is wrong and reason (R) is correct., 213

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197. Choose correct option for given statements., Assertation (A) : The molar conductivity of aq. solution of electrolyte increase when diluted by, adding water., : The dissociation of electrolyte decrease on adding water to aq. solution of, electrolyte., , Reason (R), , (A) Assertion (A) and reason (R) both are correct and R is the reason of (A), (B) Assertion (A) and reason (R) both are correct but (R) is not the reason of (A)., (C) Both assertion (A) and reason (R) are wrong., (D) Assertion (A) is wrong and reason (R) is correct., 198. The cell reaction occuring in a cell : Cd | CdCl2(0.1 M) || AgCl(s) | Ag is Cd(s), Cd 2+(aq), , + 2AgCl(s) ® 2Ag(s) +, , + 2Cl-(aq). The voltage of this cell at 273 K and 298 K is 0.6915 V and 0.6753 V, , respectively, then what will be the change in enthalpy of this reaction at 298 K ?, (A), , -167.6 KJ, , (B), , -176 J, , (C), , -234 KJ, , (D) 123.5 KJ, , 199. For the cell representations given in column-I there may be one or more than one true statements, in column-II. Join the cell representations with 4×5 matrix given for column II properly., Column-I, , Column-II, , (A) Mg(s) | Mg2+(aq.0.02M) || Cl-(aq.0.05M) | Cl2(g.1 bar) | Pt, , (P) Ecell increase if conc. of half, cell at RHS is increased keep, ing conc of half cell at LHS, constant, , (B) Pt | Br2(l) | Br-(aq.0.02M) || Au3+(aq.0.05M) | Au, , (Q) Ecell increases if conc of half, cell at LHS is increased keep, ing conc of half cell at RHS, constant., , (C) Ni(s) | Ni2+(aq.0.02M) || Cu2+(aq.0.05M) | Cu(s), , (R) Ecell increase if conc of half, cells of LHS and RHS are in, creased by same xM., , (D) Pt | Br2(l) | Br-(aq.0.02M) || Cl-(aq.0.05M) | Cl2(g.1 bar) | Pt, , (S), , Ecell increase if conc of half, cells at LHS and RHS are de, creased by same xM, , (T) QC, , >1, , (A), , P, , Q, , R, , S, , T, , (A), , P, , Q, , R, , S, , T, , (B), , P, , Q, , R, , S, , T, , (B), , P, , Q, , R, , S, , T, , (C), , P, , Q, , R, , S, , T, , (C), , P, , Q, , R, , S, , T, , (D), , P, , Q, , R, , S, , T, , (D), , P, , Q, , R, , S, , T, , 214

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200. For the electrolyses given in Column-I there may be one or more true statements in column-II., Connect the electrolyses of Column-I properly with 4 × 5 martix given for column-II., Column-I, , Column-II, , (A) On electrolysis of dilute aq. NaCl using inert, , (P) O2 gas is obtained at anode, , electrodes., (B) On electrolysis of concentrated aq. NaCl, , (Q) H2 gas is obtained at cathode., , using inert electrodes., (C) On electrolysis of aq. CuSO4 using inert, , (R) pH of solution decreases., , electrodes., (D) On electrolysis of aq. Na2SO4 using inert, , (S) pH of solution increases., , electrodes., (T) No. of spectator ions increases., (A), , P, , Q, , R, , S, , T, , (A), , P, , Q, , R, , S, , T, , (B), , P, , Q, , R, , S, , T, , (B), , P, , Q, , R, , S, , T, , (C), , P, , Q, , R, , S, , T, , (C), , P, , Q, , R, , S, , T, , (D), , P, , Q, , R, , S, , T, , (D), , P, , Q, , R, , S, , T, , Answers : 173., 181., 189., 197., , (C), (C),, (D),, (C),, , 174., 182., 190., 198., , (A) 175. (D) 176. (B) 177. (D) 178. (A), 179. (A), 180. (D),, (B), 183. (C), 184. (D), 185. (D), 186. (D), 187. (D), 188. (A),, (D), 191. (B), 192. (C), 193. (B), 194. (A), 195. (D), 196. (A),, (A)., , ˆ, , 215