6.1 What type of reaction is taking place in the cell above? 6.2 What is the reading on the voltmeter? 6.3 Switch S is now closed - NSC Technical Sciences - Question 6 - 2024 - Paper 2

The reading on the voltmeter indicates the cell potential difference. Since the voltmeter measures the cell potential, we can determine it using the standard reduction potentials for the half-reactions involved.

To calculate the reading on the voltmeter, we use the formula:

$E_{ ext{cell}} = E_{ ext{cathode}} - E_{ ext{anode}}$

Given:

• Standard reduction potential for Pb ext{^2+}/Pb is -0.13 V
• Standard reduction potential for A ext{^3+}/A is -1.66 V

Substituting these values gives:

$E_{ ext{cell}} = (-0.13) - (-1.66) = 1.53 ext{ V}$

The electrode that experiences a decrease in mass is the anode (A). At the anode, oxidation occurs, which involves the loss of electrons and results in a decrease in the mass of the electrode as metal ions go into the solution.

The net ionic cell reaction can be represented as:

$2 ext{A}^3+(aq) + 3 ext{Pb}(s) \rightarrow 2 ext{Pb}^{2+}(aq) + 3 ext{A}(s)$

This shows the conversion of lead and A ions in the electrochemical process.