Topic 4 Practice Paper: Electrochemistry — question paper

Section A: Multiple-choice questions[10 marks]

Choose one answer for each question. Each question is worth 1 mark.

1. 1

   Which of these substances can be decomposed by electrolysis?

   1. ASolid sodium chloride
   2. BPure water
   3. CMolten sodium chloride
   4. DSolid copper(II) sulfate
   ( )
2. 2

   Which electrode attracts positive ions during electrolysis?

   1. AThe cathode, because it is negative
   2. BThe anode, because it is positive
   3. CThe cathode, because it is positive
   4. DThe anode, because it is negative
   ( )
3. 3

   In the electrolysis of molten zinc chloride, what is produced at the anode?

   1. AZinc
   2. BOxygen
   3. CHydrogen
   4. DChlorine
   ( )
4. 4

   Why is graphite often used for the electrodes in electrolysis experiments?

   1. AIt is a good insulator that keeps the electrodes cool
   2. BIt is a good conductor and is unreactive with the electrolyte
   3. CIt melts easily so that it can be shaped
   4. DIt reacts with most electrolytes to speed up the process
   ( )
5. 5

   Concentrated potassium iodide solution is electrolysed with inert electrodes. Which product is released at the anode?

   1. AHydrogen
   2. BOxygen
   3. CIodine
   4. DPotassium
   ( )
6. 6

   Aqueous copper(II) chloride is electrolysed with graphite electrodes. What forms at the anode?

   1. AChlorine, because chloride ions are discharged
   2. BOxygen, because water is oxidised in preference
   3. CCopper, because copper ions move to the anode
   4. DHydrogen, because hydrogen ions are attracted there
   ( )
7. 7

   Which statement about the electrolysis of dilute sulfuric acid is correct?

   1. ABoth gases produced are hydrogen
   2. BOxygen forms at the cathode and hydrogen at the anode
   3. CNo gases are formed
   4. DHydrogen forms at the cathode and oxygen at the anode in a 2:1 ratio
   ( )
8. 8

   A metal ring is being silver-plated. What is used as the electrolyte?

   1. ADilute sulfuric acid
   2. BMolten silver chloride
   3. CA solution containing silver ions, such as silver nitrate
   4. DPure water
   ( )
9. 9

   Which of these describes what happens to the anode during electroplating?

   1. AIt stays the same mass while ions are deposited on it
   2. BIt gradually dissolves as its metal ions go into the electrolyte
   3. CIt is the object that gets coated with the plating metal
   4. DIt is made of graphite so that it does not dissolve
   ( )
10. 10

    Which is the only chemical product of a hydrogen–oxygen fuel cell?

    1. AWater
    2. BCarbon dioxide
    3. CHydrogen gas
    4. DOxygen gas
    ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided.

1. 11

   Stainless-steel cutlery is often electroplated with a thin layer of chromium.

   1. (a)

      State two reasons why the cutlery is electroplated.

      [2]
   2. (b)

      State which terminal of the power supply the cutlery must be connected to, and name the electrode it forms.

      [2]
   3. (c)

      Name a suitable electrolyte for chromium plating.

      [1]
2. 12

   During the electrolysis of molten sodium chloride, charge moves through both the wires and the electrolyte.

   1. (a)

      Describe how charge is transferred through the wires and through the electrolyte, referring to electrons and ions.

      [2]
   2. (b)

      Write the half-equation for the reduction happening at the negative electrode.

      [1]
   3. (c)

      Write the half-equation for the oxidation happening at the positive electrode.

      [2]
3. 13

   Dilute sodium chloride solution and concentrated sodium chloride solution are each electrolysed using inert electrodes.

   1. (a)

      Name the gas formed at the cathode in both experiments.

      [1]
   2. (b)

      State the gas formed at the anode in the concentrated solution.

      [1]
   3. (c)

      State the gas formed at the anode in the dilute solution.

      [1]
   4. (d)

      Explain why the gases formed at the anode are different in the two experiments.

      [2]
4. 14

   Some city buses are powered by hydrogen–oxygen fuel cells instead of diesel engines.

   1. (a)

      State the reactants of the cell and name the only product.

      [2]
   2. (b)

      Give one advantage and one disadvantage of using this cell rather than a diesel engine.

      [2]
   3. (c)

      Write the word equation for the reaction in the cell.

      [1]