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(i) Put 25 mL 0.2 M copper sulphate solution in a 100 mL polythene fitted with a 1-hole
stopper and thermometer. Replace the stopper, invert the bottle and shake it gently.
Record the temperature of this solution. Turn the bottle the right way up, remove the
stopper and add 0.5 g of zinc dust. The quantity of zinc powder is in excess to ensure that
all the copper sulphate is used up in the reaction, so some zinc will remain when the reaction
stops. Replace the stopper, invert the bottle, and shake gently. Record the highest
temperature reached. Calculate the rise of temperature. This rise of temperature in not
affected by the volume of 0.2 M copper sulphate used for the experiment. For a 1 M
solution, multiply the rise in temperature by 5 (5 X 0.2M = 1.0 M). The reactants lost
energy to the solution. The temperature change is usually between 9oC and 10oC.
Zn(s) + Cu2+(aq) --> Zn2+(aq) + Cu(s).
(ii) Repeat the experiment with 0.5 g of iron powder or iron filings. This amount is again an
excess so that all the copper sulphate will be used up in the reaction. The temperature
change is usually between 6oC and 7oC.
sharon kalunda answered the question on April 12, 2019 at 09:04
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