Year 12 Chemistry Chapter 9

When molten sodium chloride, NaCl, is electrolysed, the product formed at the cathode is

• sodium liquid, Na.

• hydrogen gas, H₂.

• chlorine gas, Cl₂.

• oxygen gas, O₂.

Initially the cell is set up with a lead, Pb, electrode as Electrode Z and 1.0 M lead nitrate, Pb(NO₃)₂, as the electroplating solution. The cell runs for a set time and current, with 1.0 g of Pb deposited onto Electrode Z.

Four subsequent electroplating cells are set up, each containing a platinum, Pt, electrode, a different Electrode Z and an appropriate 1.0 M electroplating solution. These four electroplating cells are operated for the same time and at the same current as the original Pb electroplating cell.

Which combination of Electrode Z and electroplating solution would be expected to deposit more metal by mass onto Electrode Z than the original Pb electroplating cell?

• Electrode Z chromium, Cr

  Electroplating solution

  1.0 M Cr(NO₃)₃

• Electrode Z silver, Ag

  Electroplating solution

  1.0 M AgNO₃

• Electrode Z gold, Au

  Electroplating solution

  1.0 M AuCl₃

• Electrode Z tin, Sn

  Electroplating solution

  1.0 M SnSO₄

The reaction occurring at the anode is

• 2H₂O(l) + 2e^– H₂(g) + 2OH^–(aq)

• Cu²⁺(aq) + 2e^– Cu(s)

While the circuit is closed and electrolysis is occurring, the

• concentration of Cu²⁺ ions in solution will increase due to the anode reaction.

• concentration of SO₄^2– ions in solution will drop as Cu²⁺ ions deposit on the cathode.

• concentration of the CuSO₄ solution will be unchanged.

• concentration of Cu²⁺ ions in solution will decrease due to the cathode reaction.

Which one of the following applies to a galvanic cell but not an electrolytic cell?

• The anode is positive.

• Reduction occurs at the cathode.

• Cations move towards the positive electrode.

• The cell reaction can always be reversed using electrical energy.

Using inert electrodes, three separate electrolysis experiments were conducted using 1.0 M solutions of the salts of the metals X, Y and Z. Each cell used a set current for the same time.

The mole ratio of X, Y and Z deposited was found to be 3 : 2 : 1.

The ratio of the charge on the ions of the metals X, Y and Z is likely to be

• 1 : 2 : 3.

• 3 : 2 : 1.

• 1 : 1 : 1.

• identical to the mass ratio of the metals X, Y and Z deposited.

Electrolysis of an aqueous ionic solution produces a clear gas at the anode and a deposit on the cathode. The solution is likely to be

• 4.0 M NaCl(aq)

• dilute CuBr₂(aq)

• dilute MgBr₂(aq)

• dilute CuCl₂(aq)

A current is passed through the circuit that deposits 3.17 g of copper metal on the negative electrode. The mass of silver that would be deposited in the same time would be, in g,

• 3.17

• 5.4

• 10.8

• 21.6

The total number of mole of gas evolved from this set-up will be

• 0.025

• 0.050

• 0.10

• 0.20

Using inert electrodes, three separate electrolysis experiments were conducted using 1.0 M solutions of the salts of the metals X, Y and Z. Each cell used a set current for the same time. The experiment was repeated under identical conditions except that 2.0 M solutions of the metal salts were used.

Which of the following quantities would show no change in the results for this experiment compared to the original experiment?

I the mass of each metal deposited

II the final concentration of each electrolyte

III the charge moving through each cell

• I and II only

• II and III only

• I and III only

• I, II and III