8.1 An electrochemical cell is set up using an aluminium rod, Al, and a gas X - NSC Physical Sciences - Question 8 - 2022 - Paper 2

To identify gas X, we use the following equation based on the cell potential:

$E_{cell} = E_{reduction} - E_{oxidation}$ Given: $E_{cell} = 2.89 ext{ V}, \ E_{oxidation} = -1.66 \text{ V}$ We can calculate:

$E_{reduction} = E_{cell} + E_{oxidation} = 2.89 + 1.66 = 4.55 ext{ V}$ Based on standard reduction potentials, gas X is oxygen, O₂.

The formula of the reducing agent in this cell is Al(s) (solid aluminium).

The half-reaction occurring at the cathode is:

$O_2(g) + 4 H^+(aq) + 4 e^- \rightarrow 2 H_2O(l)$

The cell notation for this electrochemical cell is:

$\text{Al}(s) | \text{Al}^{3+}(aq) || \text{O}_2(g) | \text{H}^+(aq) | \text{H}_2O(l) | Pt(s)$

Zinc (Zn) will be more suitable for storing an aqueous solution of nickel ions, Ni²⁺. This is because zinc is a stronger reducing agent than nickel and can easily reduce Ni²⁺ to nickel metal (Ni). In contrast, copper is a weaker reducing agent and will not effectively reduce nickel ions.