Monday, 10 August 2015

Electrolysis and Electrochemical Cells - Test 1

This test is on electrolysis and electrochemical cells. You may like to revise this chapter first before attempting the questions.

The total score for this test is 10 marks. You should complete the test in 10 minutes.

Section A: Multiple Choice Questions (5 marks)

1. Which of the following cannot conduct electricity.
A. copper
B. aqueous copper (II) sulfate
C. dilute hydrochloric acid
D. ethanol 

2. Inert electrodes are used in the electrolysis of the following aqueous solution. Which will not produce hydrogen gas at the negative electrode?
A. aqueous sodium hydroxide
B. aqueous copper (II) sulfate
C. aqueous iron (II) sulfate
D. dilute hydrochloric acid

3. In an electrolysis experiment, the same amount of charge deposited 32.4 g of silver and 5.9 g of nickel. The charge on the silver ion was 1+.

What was the charge on the nickel ion?
A. 1+ 
B. 2+
C. 3+
D. 4+ 

4. Inert electrodes are used in the electrolysis of 204 g of molten aluminium oxide. What is the mass of aluminium and oxygen collected?

mass of aluminium (g)
mass of oxygen (g)

5. Concentrated sodium chloride solution is electrolysed using inert electrodes. What is the ratio of the volume of gases formed at the anode to the cathode?
A. 1:1
B. 2:1
C. 1:2
D. 2:3

Section B: Open- ended questions (5 marks)
1. A student sets up an experiment to electroplate an object with copper.

(a) Show in the diagram, the direction of the flow of electrons in the external circuit.
[1 mark]
(b) Write equations, with state symbols, to show the reactions that happen at the cathode and the anode.
[2 marks]
(c) If the silver rod is replaced by graphite rod. Instead, bubbles of gases are produced at the cathode.  

(i) Suggest an identity for the gas produced at the cathode.
[1 mark]
(ii) Suggest how the concentration of copper (II) ions in the solution changes with time.
[1 mark]

Section A
1. D
2. B
3. C
4. C
5. A

Section B
1 a)

cathode: Cu2+ (aq) + 2e- ---> Cu (s)
anode: Cu (s) ---> Cu2+ (aq) + 2e-
c)i) oxygen (ii) concentration of copper (II) ions decreases with time.

Related Google App
Electrolysis - What's at the anode and cathode?

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