Write down ONE function of the part labelled X. Which electrode is the anode? Write down only Cu or Ag.

The part labelled X is the salt bridge.

• It completes the electrical circuit by allowing the movement of ions between the two half-cells.
• It maintains electrical neutrality in the half-cells by preventing charge build-up.

To determine the anode, we compare the standard reduction potentials of Cu and Ag.
$\text{Cu}^{2+}(aq) + 2\text{e}^- \to \text{Cu}(s) \quad E^\circ = +0.34 \text{ V}$
$\text{Ag}^+(aq) + \text{e}^- \to \text{Ag}(s) \quad E^\circ = +0.80 \text{ V}$
Silver has a higher reduction potential, meaning $\text{Ag}^+$ is more easily reduced (cathode). Copper has a lower reduction potential, meaning Cu is more easily oxidized (anode).

The anode is $\boxed{\text{Cu}}$.

• 8.3.1: The electrolyte in the Cu half-cell must contain $\text{Cu}^{2+}$ ions. The formula is $\boxed{\text{CuSO}_4}$ (or $\text{Cu(NO}_3)_2$).
• 8.3.2: The electrolyte in the Ag half-cell must contain $\text{Ag}^+$ ions. The formula is $\boxed{\text{AgNO}_3}$.

The standard conditions under which the cell operates are:

• Temperature of $25^\circ\text{C}$ ($298 \text{ K}$).
• Concentration of $1 \text{ mol}\cdot\text{dm}^{-3}$ ($1 \text{ M}$) for all aqueous solutions.