Part VII: Redox Reactions, Chemical Cells and Electrolysis

Consider the following reaction:

(NH₄)₂Cr₂O₇(s) → N₂(g) + 4H₂O(l) + Cr₂O₃(s)

Which element undergoes reduction?

• A. Cr

• B. H

• C. N

• D. O

In which of the following electrolyses does the electrolyte remain unchanged after the process?

• A. Electrolysing dilute sulphuric acid using platinum electrodes

• B. Electrolysing dilute sodium hydroxide solution using platinum electrodes

• C. Electrolysing copper(II) sulphate solution using copper electrodes

• D. Electrolysing copper(II) sulphate solution using graphite electrodes

In which of the following compounds does manganese have the highest oxidation number?

• A. MnCl₂

• B. MnO₂

• C. MnSO₄

• D. Mn₂O₃

Which of the following combinations is correct for the electroplating of silver on a copper object?

• A

• B

• C

• D

The diagram shows a simple chemical cell connected to a voltmeter.

For which of the following combinations of electrodes do electrons flow from electrode X to electrode Y through the external circuit?

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Which of the following items is generally powered by alkaline manganese cells?

• A. Digital cameras

• B. Emergency lighting

• C. Quartz watches

• D. Shavers

Gas M is bubbled into solution N as shown in the diagram.

Which of the following combinations of M and N will give an observable change?

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In the electrolysis of silver nitrate solution using carbon electrodes, what is the ratio of Ag(s) to O₂(g) produced?

• A. 1 : 1

• B. 2 : 1

• C. 3 : 1

• D. 4 : 1

The diagram shows a simple chemical cell connected to a voltmeter.

Electrons flow from electrode P to electrode Q in the external circuit. Which of the following statements concerning the cell is correct?

• A. Electrode Q is the anode.

• B. Reduction occurs at electrode P.

• C. The mass of electrode P increases.

• D. There will be no electron flow in the external circuit after the cell has operated for some time.

The relative positions of some metals in the Electrochemical Series are shown below.

The only oxidation number of X in its compounds is +2. Which of the following equations represents a possible reaction?

• A. X(s) + FeSO₄(aq) → XSO₄(aq) + Fe(s)

• B. 2X(s) + CuSO₄(aq) → X₂SO₄(aq) + Cu(s)

• C. Ag(s) + XNO₃(aq) → AgNO₃(aq) + X(s)

• D. 2Al(s) + 3XCl₂(aq) → 2AlCl₃(aq) + 3X(s)