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360, Modern Physical Chemistry, Electrochemistry, 2. A half-cell reaction is one that, cC+dD is, 361, (a) occurs at one clectrode, (b) goes only half way to completion, (c) involves a half mole of the concentration of the solution, RT, (a) E= Eg+, nl, (ac (ap", RT cY (apt, (b) E+E=, In, nF, (d) always oxidises, 3. Which of the following statements is not correct regarding galvanic cells ?, nRT (ac) (ap)", (a) Oxidation occurs at the anode., (c) E=En-, RT (ac (apf, In, (d) E= Eg-, (b) lons carry current inside the cell, (c) Electrons flow around the external circuit, from cathode to anode., (d) When the E.M.F. of the cell is positive, cell reaction is positive., 4. What is the overall reaction for the cell Sn I Sn2+ |I Pb2 1 Pb ?, In, nF, E.M.F. of the cell Zn I Zn"(a) I Cu+ (a2)I Cu is, a, (a), Sn2+ + Sn Pb2+ + Pb, (a) E=E-0.059 log, (b) E=E°+0.059 log, aj, Sn2+ + Pb - Pb2+ + Pb, Pb2+ + Sn, Pb2+ + H2 2H +Pb, Sn+2H H + Sn2+, (b), Sn2 +Pb, 0.059, log, a2, (c), (c) E E°-, 2., 0.059, (d) E=E°+, log, 2., (d), (e), 11. For the galvanic cell, 5. What is the overall cell reaction for the cell Cr(s) ICr (1M)II Br (IM), AgBr (s)IAg ?, ZnlZn 2 (az Cu+ (aCu)Cu, Cr+3Ag+3Br, 3Ag+ +Cr, Cr+3AgBr-, 3Ag + Cr+, Cr+3Ag Cr +3Ag, 2Cr+3Bry, (a), where a zn, acu are the activities of Zn* and Cu ions, respectively., and, (b), The E.M.F. of the cell, (c), (d), - 2Cr+6Br, (a) increases with increase of, azn, when, "Cu = constant, 6. In the cell reaction, (b) increases with decrease of ac when, aZn, = constant, Cu(s) +2Ag* (aq), -Cu (aq) +2Ag(s), (c) increase when a, decreases and, aCu, increases, the reduction half-reaction is, (d) decreases when a decreases and au increases, Cu2+ (aq) + 2e Cu(s), 2Ag (s) 2Ag (aq) +2e, 2Ag (aq)+2e 2Ag(s), Cu(s)-2e Cu (aq), 7. Free energy change (AG) is related to the E.M.FE of a cell (E) as, (a), 12. The electrode Pt I Fe+ (c). Fe (c2) belongs to the type, (a) gas electrodes, (c) amalgam electrodes, 13. According to the latest convention, the E.M.F. of a cell may be expressed in, terms of reduction potentials of RHS clectrode (ER) and LHS clectrode (E) as, (a) Ecel =EL-ER, (c) Ecell=ER+EL, (b), (c), (b) intert metal electrodes, (d), (d) metal -metal insoluble salt electrodes, nFE, RT, (b) Ecel=ER-EL, (d) Ecell=ER/E, (a) AG =, (b) AG =-, InE, RT, nF, (c) E=-NFAG, (d) AG=-nFE, 14. The equilibrium constant (K) for a cell reaction can be calculated from lhe, 8. The entropy change (AS) for a reaction is given by, standard E.M.F. of the cell (E) by the relation, nFE, (b) log K =, 2.303RT, (b) nF E-T, log E, nF, (a) nF, (a) K =, 2.303RT, 2.303, logE, (d) K =, RT, 2.303RT, -RT, (c) K =, (c)-nl, (d), In, nFE, nF, 15. The for the Ag, Ag 0/H-0. OH at the anode is

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Electrochemistry, Modern Physical Chemistry, 2Ag + 20H Ag O + H20+ 2e, Ag Ag* + e, Ag20 + H2O+ 2e Ag20+OH-, 2Ag+ H20 → Ag20+H2, 16. Chlorine gas is bubbled into a solution containing I (aq). Which equation, 362, reactions are given :, 0 Cu> Cu2+ + 2e, (ii) Sn → Sn2+ +2e, (iii) Fe → Fe2+ + 2e, (iv) Zn→ Zn2+ + 2e, which one of the following is most easily reduced?, (a), 363, (b), :E =-0.34V, (c), E=+0.14V, (d), ;E =+0.44V, ;E=+0.76V, describes the reaction., (a), F (aq) + Cl (aq) = 1(s)+Cl(g), (b) Sn, (a) Cu, The standard electrode potentials of Zn, Ag and Cu are-0.76,0.80 and 0.34, (c) Fe, (d) Zn, (b), I (aq)+C(g) =, 12(s) + Cl (aq), volts, respectively. Then, (a) Ag can oxidise Zn and Cu, (c) Zn can reduce Ag+ and Cu2+, 23 Two half cells have potentials-0.44 and 0.799 volts, respectively. These two, are coupled to make a galvanic cell. Which of the following will be true?, (a) Electrode of half cell potential -0.44V will act as anode., (b) Electrode of half cell potential-0.44V will act as cathode, (c) Electrode of half cell potential 0.799V will act as anode, (d) Electrode of half cell potential will act as positive terminal, 24. After equilibrium is reached, the voltage reading is, (b) Ag can reduce Zn+ and Cu+, (d) Cu can oxidise Zn and Ag., (c), C2(g) =, 2, I(aq)+ Cl (aq), 21 (aq)+Cl2(g) = I(s)+Cl2(g), (d), 17. The cell reaction in the cell formed by coupling the two standard electrosles, PtIH2, H (E=0) and AgIAgCl, CF (E=0.2225V) is, H2(1 atm) +Ag+(a 1) Ag(s) +H* (a 1), 2., (a), (b), H2 (1 atm) + AgCl(s), 2., H*(a= 1) +Cl (a 1)+ Ag* (a= 1, (b) 1.14, 25. The voltage measured at the instant that the switch is closed as, (a) 1.00, (c) 0.00, (d) 0.46, (c), Ag(s) + H* (a 1)+ CF (a= 1) AgCl (s) +H2 (1 atm), 2., (a) 1.00, (b) 1.15, (c) 0.00, (d) 046, 1, H2 (1 atm) + A CI (s) H (a= 1)+ CF (a= 1) + Ag (s), 26. Copper is below iron and above silver in the electrochemical series. So it is, expected that, (d), (a) copper displaces silver from silver nitrate solution, (b) copper displaces iron from ferrous sulphate solution, (c) silver displaces copper from copper sulphate solution, (d) silver displaces iron from ferrous sulphate solution., 27. The standard oxidation potentials of the electrodes AglAg*, PblPb, SnISn-", and CalCa2+ are -0.80, 0.13, 0.14 and 2.87V, respectively. The most powerful, oxidising agent among these metals is, (a) Pb, 18. When the Zn - Cu cell is used to produce electrical energy, cations, (a) move towards the Zn electrode, anions to the Cu., (b) move towards Cu, anions toward Zn, (c) and anions move towards Zn, (d) and anions move towards Cu., 19. If the half cell-reaction X+eX-has a large negative reduction poten, it follows that, (b) Ca, (c) Sn, (d) Ag, (a) the oxidised state is favoured, 20. The standard reduction potential values of the elements Mj, M2 and M3 are, 0.34V, 3.05V and 1.66V, respectively. The order of their reducing power, will be, (b) there is great tendency for the substance to accept electrons, (c) the cell reaction will go on spontaneously in the direction indicate, (d) X is readily reduced, 20. Zn is coated over iron to prevent rusting of iron because, (b) M3 > M2 > M, (d) M2> M3> M, (a) M1 > M2> M3, (c) M1> M3> M2, (a) it is cheaper than iron, (Fe Fe), (c) E, 21 The values of the standard oxidation electrode potentials of the folloW:, -0.44V. Which of the following is correct?, (a) Zn will reduce Fe2+, (b) Zn will reduce Mg2+, (d) Zn oxidises Fe., (2n /n), (d) E, Zn Z, (Fe Fer, (c) Mg oxidises Fe, 30. For the in the 4G =-, 29. E° value of Mg2+ | Mg is- of Zn2+1 Zn is 0.76V and of Fe2 I Fe is

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Electrochemistry, (d) all the above., 364, Modern Physical Chemistry, 365, nFE° is, (a) NaCl, (b) KCI, (c) LiCI, (d) 12, (a) 1, 31. For a certain redox reaction. E is positive. It means that, (a) AG° is positive. K is greater than I, (b) AG° is positive, K is less than I, (c) AG is negative, K is greater than., (d) AG° is negative, K is less than 1, 32. What does a negative E.M.F. for a cell indicate ?, (a) Electrons flow through the external circuit in the reverse direction, (b) The opposite half-cell reactions take place spontantaneously, (c) The reactions as written are not spontaneous, (b) 2, (c) 3, (d) CSCI, RT, (a) E=-, In 2, nF, RT, (b) E=, log, 2.303RT, log, RT, (c) E=, (d) E=-, In, nF, nF, as, 10 The E.M.F. of a concentration cell without liquid junction potential is, RT, In, nF, E =-, (d) All of the above, where, 33. The calomel electrode is, (a) Ci<c2, (b) c1>c2, (a) a standard hydrogen electrode, (b) present in dry cell, (c) a reference electrode, (c) c1=C2, 41. In the fucl cell employing the reaction, (d) the equation is incorrect, (d) another name for mercury electrode, 34. The most commonly used reference electrode is, CH +202C0, +2H,0, (a) carbon is reduced, (c) CH4 and CO2 react at the same electrode, (d) chemical energy is converted directly to electrical energy, 42. Which of the following reactions could serve as a source of energy in a fuel, (b) hydrogen is oxidised, (a) the hydrogen electrode, (c) the glass electrode, 35. For the electrode Agl AgCl(s), HCI, the half-cell reaction is, (b) the calomel electrode, (d) all of these, (a), Ag Ag+ + e, Ag++Cl AGCI, cell?, (b), (a), H2O(1) →, H2(g) +,O2(g), 1, (c), H* + AgCl + e →, H2 + Ag + Cl2, 2, (b), Ag+ Cl → AgCl +e, 36. If 2.303 RT/F=0.059 and the standard potential of the reference electrode is, XV, the pH of the solution can be calculated from the E.M.F. (E) of the cell, Zn(s) + Cu2+ (aq) → Zn2* (aq)+Cu(s), CO2 (g) → C(s) +O2(g), C(s) +O2(g) CO2(g), (d), (c), (d), 43. A mixture of fuel gases is fed to anode. The gases are absorbed by catalyst,, activated and caused to react in the electrolyte. This reaction releases a, stream of electrons making direct current, Meanwhile at the cathode, oxygen, Is absorbed and reacts with incoming current to complete the chemical and, electrical circuit. The overall process yields water and CO2, plus ciecineny, The above is a description of, (a) regeneration, (c) a battery, Reference electrode IIH (a, ).H,(latm)l Pt, using equation, E+X, 0.059-X, (a) pH =, 0.059, (b) pH =, (b) reduction, E-X, (c) pH =-, E, (d) pH =0.059x, (d) a fuel cell, 0.059, 37. The function of a salt bridge in an clectrochemical cell is, Fet +3e Fets) is, (a) to prevent the mixing of the clectrolyte in the two half cells, (b) to complete the circuit, (c) to maintain clectrical neutrality of the two half cells., (a) 10.13KJ, (b) 5.12kJ, (e) 20.84 kJ, (d) 3.47KJ

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Electrochemistry, (d) all the above., 364, Modern Physical Chemistry, 365, nFE is, (a) NaCl, (b) KCI, (c) LCI, (b) 2, (c) 3, (d) 12, (d) CSC1, (a) 1, 31. For a certain redox reaction. E is positive. It means that, (a) AG is positive. K is greater than I, (b) AG° is positive, K is less than 1, (c) AG is negative, K is greater than., RT, In 2, RT, (b) E= -, log ", nF, (а) E3-, nF, (d) AG° is negative, K is less than 1, 2.303RT, log, nF, RT, 32. What does a negative E.M.F. for a cell indicate ?, (a) Electrons flow through the external circuit in the reverse direction, (b) The opposite half-cell reactions take place spontantaneously, (c) The reactions as written are not spontaneous, (c) E =, (d) E=, In, nF, 40. The E.M.F. of a concentration cell without liquid junction potential is, RT, In, nF, E = -, where, (d) All of the above, C2, 33. The calomel electrode is, (a) ci<c2, (a) a standard hydrogen electrode, (b) present in dry cell, (c) a reference electrode, (c) C1 = C2, 41. In the fuel cell employing the reaction, (b) C1>c2, (d) the equation is incorrect, CH +202- CO, +2H,0, (d) another name for mercury electrode, 34. The most commonly used reference electrode is, (a) the hydrogen electrode, (c) the glass electrode, 35. For the electrode Ag I AgCl(s), HCI, the half-cell reaction is, (a) carbon is reduced, (c) CH4 and CO2 react at the same electrode, (d) chemical energy is converted directly to electrical energy, 42. Which of the following reactions could serve as a source of energy in a fuel, (b) hydrogen is oxidised, (b) the calomel electrode, (d) all of these, Ag Ag+ +e, Ag+ + Cl → AgCl, (a), cell ?, (b), H2(e)+, 02(g), (a), H2O(1) →, (c), H + AgCl +e →, H2 + Ag +Cl2, Zn(s) +Cu2+ (aq) → Zn2+ (aq) + Cu(s), CO2 (g) → C(s)+O2(g), C(s) +O2(g) → CO2(g), (b), Ag+Cl → AgCl +e, (d), 36. If 2.303 RT/F=0.059 and the standard potential of the reference electrode is, XV, the pH of the solution can be calculated from the E.M.E (E) of the cell, (c), (d), 43. A mixture of fuel gases is fed to anode. The gases are absorbed by catalyst,, activated and caused to react in the electrolyte. This reaction releases a, stream of elcctrons making direct current. Meanwhile at the cathode, oxygen, Is absorbed and reacts with incoming current to complete the chemical ane, electrical circuit. The overall process vields water and CO2, plus clectricny., The above is a description of, (a) regeneration, (c) a battery, Reference electrode HH (a).H (latm)lPt, using equation, E+X, 0.059 -X, (a) pH =, (b) pH =, 0.059, (b) reduction, E- X, E, (d) pH=0,059x, (d) a fuel cell, (c) pH= -, 0.059, 37. The function of a salt bridge in an clectrochemical cell is, Fe+, +3c Fets) is, (a) to prevent the mixing of the electrolyte in the two half cells, (b) to complete the circuit, (c) to maintain electrical neutrality of the two half cells., (a) 10.13kJ, (b) 5.12KJ, (c) 20.84 kJ, (d) 3.47KJ

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Electrochemistry, through the cell., ) The Nernst equation gives the ....E.M.E of the cell, À In concentration cells, electrical energy arises from the transfer of a, from a solution of higher activity to one of lower activity., 367, 366, Modern Physical Chemistry, =(0,80V and E, = 0.34. The E.M.E of the cell, 45. Given E, (Cu Cu), (Ag Ag), CulCu2+(a 1)llAg (a 1)lAg is, (c) 0.80V, (d) -0.46V, 54. Write as True (T) or False (F):, (a) 046V, (b) 1.14V, o In an electrochemical cell, oxidation occurs at anode while reduction, 46. What is the standard E.M.F for the cell SnlSn2+ I| Pb2+ I Pb?, Sn2t +2eSn; E°=-0.14V, Pb2+ +2ePb; E° =-0.13V, occurs at cathode,, () For a cell reaction to occur spontaneously in a given direction, the E.M.E., of the cell should be + ve., GiD The equilibrium constant (K) for a cell reaction is related to the E.M.E., as log K=nFE/2.303 RT., (iv) The concentration dependence of the E.M.F. of acell is given by Gibb's-, Helmholtz equation., (v) The E.M.F. of the cell Znl Zn2 (a1) | Cu (az)|Cu at 298 K is given by, Given:, (a) -0.27V, (b) -0.01V, (c) +0.01V, (d) +0.27V, 47. The E.M.F. of the cell, Zn IZn2+ (a 0.1)| CF (a=0.1), Cl2 | Pt, (ZnZn)= -0.76V and E°, (b) 0.6V, 48. Calculate E for Zn electrode at 25°C in which [Zn2+] is 0.025M., E° for Zn Zn2+ +2e- is 0.763 volts, = 1.36V, (Cl, CI), (c) -0.6V, when E, (a) 2.12V, (d) -2.12V, E=E°-0.059 log (a/a), ANSWERS, (b) +0.405 V, (d) +0.810V, 2. (a);, 1. (b);, 7. (d);, 3. (a);, 4. (c);, 5. (a);, 11. (ct., 17. (d);, 6. (c);, 12 (b):, (a) -0.405V, 9. (d);, 8. (a);, 14. (b);, 20. (c);, (c) -0.810V, 10. (c);, 49. Using E° values calculate the value of the equilibrium constant for the follo-, wing reaction at 298K:, 13. (b);, 15. (а);, 16. (b):, 18. (b):, 19. (a);, 21. (a);, 22. (c);, 23. (a):, 24. (a);, 30. (d), E° =-0.14V, Sn2+ + 2e Sn, Zn2+ + 2e Zn, 25. (d);, 26. (a);, 27. (d);, 28. (d), 29. (a);, E° =-0.76V, 32. (b);, 35. (c):, 36. (c), 31. (c);, 37. (d);, 43. (d);, 33. (с);, 34. (d);, (c) 5.1x 1020, (d) 3.9x 1010, (а) 21.18, 50. The potential of a hydrogen electrode in an aqueous solution is 0.59V at 25°C., The pH of the solution is, (b) 9.6x 1020, 41. (d):, 42 (d):, 39. (а);, 45. (a);, 38. (b);, 40. (b):, 44. (a);, 46. (c);, 47. (a):, 48. (d):, 49. (b);, 50. (а);, 53. (1) opposite, (iv) negligible, (vi) substance;, (1) T;, 51. (d);, 52. (c);, (a) 10, (b) 1, (c) 5.9, (d) 4, (iii) spontaneous, (v) concentration dependence, (ii) low, 51. Hydrogen electrodes are placed in two solutions of pH= 5 and pH=8 at 25°C., A salt bridge links the solutions. What is the E.M.F. of the cell thus constr-, ucted ?, (d) 0.177V, 54,, (ii) T;, (ii) T;, (iv) F, (a) 0.327V, 52. A cell contains two hydrogen electrodes. The negative electrode is in cont-, act with a solution of 10-6 M hydrogen ions. The E.M.F. of the cell is 0.118V, at 25°C. The concentration of H+ ions at the positive electrode is, (b) 0.277V, (c) 0.227V, (v) F., (d) 10- M, (a) 10-M, 53. Fill in the blanks in the following:, (i) The potential for the same electrode, when acting as an anode is of the, (b) 10M, (c) 10 M, sign to its potential when it acts as a cathode., (ii) For pH determination, the quinhydrone electrode works satisfactorily only, al ..... pH value., (iii) A positive value for the E.M.F. of the cell indicates a . . process in, the given direction., (iv) In case of reversible electrode processes, amount of current flows