1

ELECTROLYSIS

Inert Electrodes

Example 3,

Q2, Q5, Q7, Q8b, Q11, Q14, Q15

Active electrodes/Electroplating/Purifying

Q1, Q3, Q9, Q10, Q16, Q17

Simple Cells

Q4, Q8a, Q12 (fuel cell), Q13, Q16a

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ELECTROLYSIS

Q1 Q2

3

Q3

Q4

4

5

Q6 Chlorine can be manufactured by the electrolysis of concentrated sodium chloride solution using the following set-up where X and Y are

the inert electrodes:

a) Which electrode X or Y is the cathode? Explain your answer.

b) Write down the ionic equation for the reaction at electrode X,

c) Other than hydrogen gas, name another product formed in the solution

around Y.

d) Suggest the function of the diaphragm.

e) Describe one confirmatory test for the gas produced at the anode.

6

Q7

7

Q8

8

Q9

9

Q10

10

Q11

11

Q12 The NASA space shuttle uses fuel cells to generate electricity. The diagram below shows a hydrogen-oxygen fuel cell.

The overall reaction in the fuel cell is the reaction between hydrogen and

oxygen to make water.

(a) Give one source for hydrogen and one source for oxygen for use in a

fuel cell.

(b) What is the name of the electrolyte used in the fuel cell?

(c) What type of reaction takes place, reduction or oxidation, at the

positive electrode? Explain your answer.

(d) A fuel cell uses 240dm3 of hydrogen. Calculate the volume of oxygen

needed, and the mass of water formed. All gas volumes measured at

room temperature and pressure.

(e) Describe two advantages and one disadvantage of using a fuel cell to

generate electricity

12

Q13 The diagram below was used to investigate the relative reactivity of various metals, A, B, C and D.

The metal strips and copper were first cleaned with sandpaper.

Various metal strips were connected in turn with the copper sheet and

the voltage recorded.

(a) Explain why the metal strips and the copper sheet were first cleaned

with sand paper.

(b) Which of these metals is/are less reactive than copper? Explain your

answer in terms of electron flow and the results shown in the table.

(c) From the results shown, arrange the four metal A, B, C and D in

decreasing order of reactivity.

(d) Given that A is an element in group II of the Periodic Table, what would

happen if it was placed in copper(lI) sulfate solution? Give an ionic

equation for the reaction involved.

(e) Explain any difference in the voltmeter readings if the above

experiments were repeated using a piece of filter paper soaked in

tetrachloromethane instead of in sodium chloride solution.

13

Q14

14

Q15

15

Q16

16

17

Q17