Question

When 4A of current is passed through a 1.0L, 0.10 M Fe\(^3+\)(aq) solution for 1 hour, it is partly reduced to Fe(s) and partly to Fe\(^2+\)(aq). Identify the incorrect statement.

• A. 0.10 mole of electrons are required to convert all Fe\(^3+\) to Fe\(^2+\)
• B. 0.025 mol of Fe(s) will be deposited
• C. 0.075 mol of iron remains Fe\(^2+\)
• D. 0.050 mol of iron remains as Fe\(^2+\)

Hint:

Remember Faraday's law: the number of moles of electrons required for reduction is proportional to the number of moles of ions being reduced.

Answer 1

The Correct Option is C

The total charge passed is \( Q = I \times t = 4 \, {A} \times 3600 \, {s} = 14400 \, {C} \). The number of moles of electrons is given by \( n = \frac{Q}{F} = \frac{14400}{96500} = 0.149 \, {mol} \). For Fe\(^3+\) to Fe\(^2+\), 1 mole of Fe\(^3+\) requires 1 mole of electrons. Therefore, 0.149 mol of electrons will convert 0.149 mol of Fe\(^3+\) to Fe\(^2+\). The incorrect statement is (c), as 0.075 mol of Fe remains Fe\(^2+\), which does not match the calculated result.