Q24 / 150 · MHT CET 2026 (16 April Shift 1) · Chemistry
The cells A and B contain aqueous solutions of ferrous chloride and ferric chloride respectively. The mass of iron deposited by the same quantity of electricity in cells A and B is in the ratio.
- A$1:1$
- B$2:1$
- C$3:1$
- Correct answerD$3:2$
Solution
In cell A, ferrous chloride ($\text{FeCl}_2$) contains iron in the $+2$ oxidation state. The reduction reaction is:
$\text{Fe}^{2+} + 2e^{-} \rightarrow \text{Fe}$
The equivalent weight of iron in cell A is $E_A = \dfrac{M}{2}$, where $M$ is the atomic mass of iron.
In cell B, ferric chloride ($\text{FeCl}_3$) contains iron in the $+3$ oxidation state. The reduction reaction is:
$\text{Fe}^{3+} + 3e^{-} \rightarrow \text{Fe}$
The equivalent weight of iron in cell B is $E_B = \dfrac{M}{3}$.
According to Faraday's second law of electrolysis, the mass of a substance deposited by the same quantity of electricity is directly proportional to its equivalent weight. Thus, the ratio of the mass of iron deposited in cell A to that in cell B is:
$\dfrac{m_A}{m_B} = \dfrac{E_A}{E_B} = \dfrac{\dfrac{M}{2}}{\dfrac{M}{3}} = \dfrac{3}{2}$
The ratio is $3:2$.
Answer: $3:2$
$\text{Fe}^{2+} + 2e^{-} \rightarrow \text{Fe}$
The equivalent weight of iron in cell A is $E_A = \dfrac{M}{2}$, where $M$ is the atomic mass of iron.
In cell B, ferric chloride ($\text{FeCl}_3$) contains iron in the $+3$ oxidation state. The reduction reaction is:
$\text{Fe}^{3+} + 3e^{-} \rightarrow \text{Fe}$
The equivalent weight of iron in cell B is $E_B = \dfrac{M}{3}$.
According to Faraday's second law of electrolysis, the mass of a substance deposited by the same quantity of electricity is directly proportional to its equivalent weight. Thus, the ratio of the mass of iron deposited in cell A to that in cell B is:
$\dfrac{m_A}{m_B} = \dfrac{E_A}{E_B} = \dfrac{\dfrac{M}{2}}{\dfrac{M}{3}} = \dfrac{3}{2}$
The ratio is $3:2$.
Answer: $3:2$
Hence, the correct answer is option: 'D'.