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Miracle Learning Centre Chemistry Tuition Question on Electrolysis. (O Level Chemistry) Write the answers in the blanks provided.

1 A constant current was passed through aqueous copper (II) sulfate using inert electrodes as shown in the diagram. (a) Name a suitable material for the inert electrodes. ……………………………………………………………………………… (b)(i) At which electrode was copper deposited? ……………………………………………………………………………… (ii) Write an equation to represent the above reaction. ……………………………………………………………………………… (c)(i) What was observed at the other electrode? ………………………………………………………………………………

(ii) Write an equation to represent the reaction happening at this electrode. ……………………………………………………………………………… The electrode at which the copper was deposited was removed at intervals, washed, dried and weighted. The results are shown in the table below. Time / min Mass of cathode / g Total increase in mass / g 0 7.55 0.00 10 8.00 0.45 20 8.45 0.90 30 8.90 40 9.35 50 9.80 60 9.80 (d) (i) Complete the table by calculating the total increase in mass after each 10 minute interval. ……………………………………………………………………………… (ii) Plot a graph showing the increasing mass of the cathode over time.

iii) How long did it take for 1.60g of copper to be deposited? ………………………………………………………………………………

(iv) Suggest why the last two readings were the same. ……………………………………………………………………………… Answer 1a) Carbon; or Platinum; (b)(i) B; (ii) Cu2+ + 2e → Cu; (c)(i) Bubbles of gas; (ii) 4OH- → 2H2O + O2 + 4e (d)(i) 1.35, 1.8, 2.25, 2.25; (ii) 1 mark for correct plotting of points; (iii) 36 – 37 min; (iv) No more copper is being deposited; Learn from our Chemistry Tuition Question and Answers. Miracle Learning Centre Call 6463 8756 or sms 9839 9908. (Specialist in Science and Maths)