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Aim, Performing and observing the actions of1., 2., 3., 4., , Water on quicklime, Heat on ferrous sulphate crystals, Iron nails dipped in copper sulphate solution, Reaction between sodium sulphate and barium chloride solution, , On the following reactions1., 2., 3., 4., , Combination reaction, Decomposition reaction, Displacement reaction, Double displacement reaction, , EXPERIMENT 3(a) - COMBINATION REACTION, Materials Required, 1., 2., 3., 4., 5., 6., 7., , Quick lime (Calcium oxide), Borosil beaker, Glass rod, Distilled water, Dropper, Test tube, Litmus paper strips, , Theory, , When calcium oxide (quicklime) is dissolved in water, it forms calcium hydroxide, (slaked lime). The reaction is highly exothermic, i.e. a lot of heat is produced during the, reaction., This reaction may be represented in the form of a chemical reaction as follows:, , Note: Calcium hydroxide is basic in nature., Therefore, it turns moist red litmus paper blue. If we pass CO2 through clear calcium, hydroxide solution (lime water), it turns milky due to the formation of a white

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precipitate (insoluble calcium carbonate)., , In reaction (i), two compounds-quicklime and water combine to give a single product, slaked lime. So, this is an example of combination reaction. Hence, it may be stated that, when two or more substances react together to form a single product, is called a, combination reaction., Also, it has been observed that a large amount of heat is evolved along with the, formation of products. Such type of reactions which are accompanied by the evolution, of heat, are called exothermic reactions., Procedure, 1. Take a small amount of quicklime in a borosil beaker or hard glass beaker. Slowly, add water to it as shown in Fig. 1 (a)., 2. Stir it well with a clean glass rod as shown in Fig. 1(b)., , 3. Observe what happens. Touch the beaker carefully., 4. Classify the reaction., 5. Using a clean dropper, take a few drops of the solution formed in the beaker and, place them on red and blue litmus paper strip (as shown in Fig. 2). Make your

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observation., , Observation, The hissing sound is produced and solution becomes hot. The heat is evolved during the, reaction which raises the temperature of the reaction mixture. On putting a few drops of, the solution on red and blue litmus paper, it is observed that only red litmus paper turns, blue, no changes occur in blue litmus paper., Conclusion, In this reaction, quicklime (CaO) and water (H2O) combine to give a single product, slaked lime [Ca(OH)2 ]., CaO(s) + H2O (l) ——–> Ca(OH)2 (aq) + Heat, It is a combination reaction and calcium hydroxide [Ca(OH)2 ] is basic in nature., As heat is evolved, the reaction is exothermic., , Precautions to be taken during the Experiment, ●, , Take a small amount of compound such as quick lime to perform the experiment., , Since the reaction is exothermic avoid touching the mixture directly., ● Carefully pour water to the borosil beaker containing calcium oxide (quick lime)., ● Calcium oxide causes severe burns and therefore it should be handled with a, spatula., ● Use good quality glass beaker during the experiment because if the beaker is of poor, quality then there are chances of crack on the beaker due to the exothermic reaction., ●, , ********************************************, EXPERIMENT 3(b)-DECOMPOSITION REACTION

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Materials Required, Ferrous sulphate crystals (2g), boiling tube, test tube holder, safety glass (goggle),, Bunsen burner, blue and red litmus paper strips., Theory, The ferrous sulphate crystals are actually ferrous sulphate heptahydrate (FeSO4.7H2O)., They contain seven molecules of water of crystallisation. These crystals are green in, colour., Heating of Ferrous Sulphate Crystals, When the green coloured ferrous sulphate heptahydrate crystals (FeSO4.7H2O) are, heated, they first lose seven molecules of water of crystallisation to form anhydrous, ferrous sulphate (FeSO4 ) which is white in colour., When this anhydrous ferrous sulphate is heated, it decomposes to give ferric oxide,, sulphur dioxide and sulphur trioxide., The reactions may be represented as:, , In this reaction, one substance FeSO4(s) is splitting up into three substances Fe2O3(s),, SO2(g), SO3(g) because it takes place due to heat., So, this is a decomposition reaction. It is actually a thermal decomposition reaction., On combining Eqs. (i) and (ii), we can write the reaction as:, , Procedure, 1. Take about 2g ferrous sulphate crystals in a boiling tube., 2. Note the colour of ferrous sulphate crystals., 3. Hold the boiling tube in a test tube holder.

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4. Heat the boiling tube (as shown in Fig. 1) and observe the odour of gases evolved, and colour of residue formed., , 5. Steamy fumes are given out which condense to form tiny droplets of a colourless, liquid at the neck of boiling tube. Test the nature of these droplets with the help of, blue and red litmus paper., 6. Smell if any gas evolved by turning it gently towards your nose with a blow of, your hand (as shown in Fig. 2).

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7. Bring a wet blue and red litmus paper near the mouth of the boiling tube (as, shown in Fig. 3) and observe the change., , 8. Classify the reaction., Observation, 1. The green colour of ferrous sulphate crystals first changes to white and then a, brown solid is formed (which is ferric oxide, Fe2O3)., 2. Both red and blue litmus paper do not show any change in colour with tiny, droplets, formed at the neck of boiling tube., 3. Gas having the smell of burning sulphur comes out of the boiling tube., 4. Moist blue litmus paper turns red when it comes in contact with evolved gas., Conclusion, When ferrous sulphate is heated strongly, it decomposes to form ferric oxide,, sulphur dioxide and sulphur trioxide, so this is a decomposition reaction., ● The tiny droplets, formed near the cooler parts of the boiling test tube are of, water. That’s why, it is neutral to red and blue litmus paper., ● Oxides of sulphur (SO2 and SO3) turns blue litmus paper red. Therefore, gases have, acidic nature., ● The decomposition of ferrous sulphate is carried out by heating, so it is, called thermal decomposition reaction., ●, , Result, Heating of ferrous sulphate crystals is a decomposition reaction and it decomposes to, give ferric oxide (Fe2O3), sulphur dioxide (SO2) and sulphur trioxide (SO3).

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Precautions, ●, ●, ●, ●, ●, , Keep the mouth of the boiling tube away from yourself and your neighbour., Smell the gas by turning it gently towards your nose with a blow of your hand and, not by bringing the mount of boiling tube under your nose., Wear the safety glass while performing this experiment., While heating FeSO4.7H2O crystals, use a hard glass test tube (boiling tube) which, is perfectly dry., Keep the fumes of SO2 and SO3 gases away from your eyes as this may cause, irritation to the eyes., ****************************************************************************, EXPERIMENT 3(c) – Displacement Reaction, , Materials Required, Two test tubes, two iron nails, beaker, measuring cylinder, a piece of sand paper,, distilled water, copper sulphate solution, thread, laboratory stand with clamp, test tube, stand., Theory, According to the reactivity series, a more reactive metal displaces a less reactive metal, from its salt solution. Iron is placed above copper in the activity series. Elements placed, above in this series are more reactive than those placed below them., Thus, iron is more reactive than copper. When iron nails are placed in blue coloured, copper sulphate solution, iron displaces copper from CuSO4 solution to form ferrous, sulphate FeSO4, while the grey coloured iron nails gets covered by a brownish-red, deposit of copper metal., , In this reaction, since the metallic iron has displaced copper ion (Cu2+ )from its salt, solution, it is an example of a chemical displacement reaction. In this reaction, metallic, iron is converted into ferrous iron (Fe2+) and cupric ion (Cu2+) is converted into metallic, copper., , Procedure

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1. Take two iron nails and clean them with a sand paper., 2. Take 20 ml of distilled water in a clean test tube and dissolve copper sulphate, crystals in it. Label this test tube as A., 3. Transfer about 10 mL of copper sulphate solution from test tube A to another, clean test tube. Label this test tube as B., 4. Take one iron nail tied with a thread and immerse it carefully in copper sulphate, solution in test tube A for about 15 min [as shown in Fig. 1]. Keep the another iron, nail separately for comparison afterwards., 5. After 15 minutes, take out the iron nail from the copper sulphate solution., , 6. Compare the intensity of blue colour of copper sulphate solution before and after, the experiments in test tubes A and B and also compare the colour of iron nail, dipped in copper sulphate solution with the one kept separately [Fig. 2], Record, your observations., , S. No., , Property, , Before experiment, , After experiment

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1., , Colour of copper sulphate solution, , Blue, , Green, , 2., , Colour of iron nail, , Silvery grey, , Brownish red coating, , Observation Table, , Result, The initial colour of copper sulphate solution in the test tube is blue and iron nails are, silvery grey. After being dipped in copper sulphate solution for about 15 min, the blue, colour of copper sulphate solution turns light green and the surface of iron nails get, covered with brownish red coating., It is a displacement reaction as iron displaces copper from the copper sulphate solution, to form copper and ferrous sulphate., Fe (s) + CuSO4 (aq) ———> FeSO4 (aq) + Cu (s), Precautions, The iron nails must be cleaned properly by using sand paper before dipping them, in copper sulphate solution., ● Prepare a dilute copper sulphate solution in distilled water. If it is a concentrated, solution, then it may not be possible to see the change in its colour after the, experiment., ● Use good quality of boiling tube., ●, , ********************************************************************************, EXPERIMENT 3(d) – Double displacement reaction, Materials Required, Two test tubes, test tube stand, a conical flask, a glass rod, sodium sulphate solution,, measuring cylinder and barium chloride solution., Theory, Those reactions in which two ionic compounds in the solution react by exchange of, their ions to form new compounds are called double displacement reactions., The ionic compounds taken as reactants are soluble in water. However, one of the

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products formed is either insoluble and separates out as a solid, called precipitate or it, is a gas and other product is soluble in the solution., When a solution of sodium sulphate is mixed with a solution of barium chloride, the, following double displacement reaction takes place:, , In this reaction, sulphate ions (SO4 ) from sodium sulphate are displaced by chloride, ions (Cl–) and chloride ions from barium chloride are displaced by sulphate ions., As a result, a white precipitate of barium sulphate is formed and sodium chloride, remains in the solution., Procedure, 1. Take two clean test tubes and label them as A and B., 2. In test tube A, take the solution of barium chloride (5 ml.) and observe the colour, of the solution., 3. In test tube B, take the solution of sodium sulphate (5 ml) and observe the colour, of the solution (as shown in Fig.1)., , 4. Transfer carefully the solutions of test tubes A and B in a conical flask (as shown, in Fig. 2)., 5. Stir the two solutions by using glass rod and leave it undisturbed for some time.

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6. Observe the change in colour of the solutions as per the steps given in observation, table ahead., , S.No., , Experiment, , Observations, , Observe the colours of both solutions in test tubes A and B before mixing, 1., , Colourless, them., , Mix both the solutions and leave the mixture undisturbed for some time. White colour, 2., Does anything precipitates in the test tube? if so, what is the colour of it? precipitate is forme, , Observation Table, , Result, Solutions of sodium sulphate and barium chloride both are colourless. On mixing the, solution of sodium sulphate and barium chloride, a white precipitate is formed. This, reaction is an example of a double displacement reaction, since two different salt, solutions have exchanged ions to form two new salts, i.e. barium sulphate (white ppt)

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and sodium chloride., , Precautions, ●, ●, ●, ●, ●, , Test tubes, beaker and glass rod should be cleaned., Equal volume of sodium sulphate and barium chloride should be used., Add barium chloride solution very slowly to the sodium sulphate solution and stir, with a glass rod., Do not touch or taste the chemicals., Do not fill more than one-third of the test tube with sodium sulphate solution., ***************************************************************************, , Experiment - 4, Aim, To show experimentally that carbon dioxide is given out during respiration., , Theory, All living things show respiration., ● It is a chemical process that occurs inside the cell, hence called cellular, respiration., ● It involves the breaking down of food to release energy and carbon dioxide., ● Its reaction is the reverse of photosynthesis., ●, , There are two types of respiration in animals: Aerobic and anaerobic respiration., ● Aerobic respiration needs oxygen and anaerobic respiration occurs in the absence, of oxygen., ●

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●, , There are three pathways of respiration as shown below:, , ●, , The energy released in cellular respiration is immediately used to synthesise a, molecule called ATP., Plants also release CO2 during respiration., The exchange of gases during respiration takes place through small pores on the, leaf called stomata., Carbon dioxide can be tested by lime water test., A freshly prepared lime water is Ca(OH)2 When CO2 is allowed to pass through it, an insoluble compound called CaCO3 is formed which makes the lime water milky., , ●, ●, ●, ●, , (A) Test for release of CO2 during respiration in animals., Materials Required, Two test tubes, a cork with two holes, two glass tubes, syringe, lime water., Procedure, 1., 2., 3., 4., 5., , Take some freshly prepared lime water in two test tubes., Fit cork with two holes in test tubes A and B., Fix two glass tubes in this cork of test tube A as shown in the figure., Exhale air into the tube and record your observations., In another test tube B, which has lime water, pass air through syringe and record, your observations., , Observation

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●, , In test tube A, the lime water turns milky sooner than in test tube B., , Conclusion, 1. The exhaled air contains lot of CO2 which turns lime water milky., 2. This proves that during respiration we exhale CO2 gas., Precautions, 1. The glass tube should be dipped in the lime water., 2. The lime water should be freshly prepared., (B) To test release of C02 by plants during respiration., Materials Required, A conical flask, small test tube, cork, thread, germinating seeds, a bent tube, a beaker,, water and freshly prepared lime water., , Procedure, 1. Take two conical flasks, add germinating seeds with little water sprinkled over it., 2. Fix the mouth of conical flasks with cork in which a bent tube is fixed., 3. Suspend a small test tube containing KOH solution in it with the help of a thread, in conical flask A., 4. Allow the mouth of the bent tube to be immersed in water in set-up A and in lime, water in set-up B as shown below., 5. Record your observations after few hours., , Observations, 1. In set-up A, the water level in the bent tube dipped in beaker increases after few, hours.

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This is because the oxygen present in the conical flask is taken up by germinating, seeds and CO2 released due to respiration is absorbed by KOH present in small, tube. Hence, the air pressure in the flask reduces and water level rises., 2. In set-up B, the freshly prepared lime water turns milky. This is due to excess, CO2 released into the test tube during respiration of germinating seeds., Conclusion, This shows that CO2 is given out during respiration., Precautions, 1. Lime water should be freshly prepared., 2. KOH solution should be freshly prepared., 3. Germinating seeds should have lot of moisture in them.