Question:
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.
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.
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Moles of Fe deposited per faraday are 1/2 for Fe2+ and 1/3 for Fe3+.
Updated On: Oct 1, 2026
- \(1:1\)
- \(2:1\)
- \(3:1\)
- \(3:2\)
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The Correct Option is D
Solution and Explanation
Step 1: Understanding the Concept:
Faraday's law: for the same charge, the mass deposited is proportional to the equivalent mass, i.e. \(M/z\), where \(z\) is the number of electrons needed per ion.
Step 2: Detailed Explanation:
Cell A (ferrous chloride): \(\text{Fe}^{2+} + 2e^- \rightarrow \text{Fe}\), \(z = 2\).
Cell B (ferric chloride): \(\text{Fe}^{3+} + 3e^- \rightarrow \text{Fe}\), \(z = 3\).
\[ \frac{m_A}{m_B} = \frac{M/2}{M/3} = \frac{3}{2} \]
The mass of iron in cell A is 1.5 times that in cell B. Options (A), (B) and (C) come from ignoring the charge on the ion or inverting the ratio.
Step 3: Final Answer:
The ratio is \(3 : 2\), option (D).
Final Answer:
Mass deposited goes as 1/z, so the ratio is 3 to 2. \[ \boxed{\text{(D) }3:2} \]
Faraday's law: for the same charge, the mass deposited is proportional to the equivalent mass, i.e. \(M/z\), where \(z\) is the number of electrons needed per ion.
Step 2: Detailed Explanation:
Cell A (ferrous chloride): \(\text{Fe}^{2+} + 2e^- \rightarrow \text{Fe}\), \(z = 2\).
Cell B (ferric chloride): \(\text{Fe}^{3+} + 3e^- \rightarrow \text{Fe}\), \(z = 3\).
\[ \frac{m_A}{m_B} = \frac{M/2}{M/3} = \frac{3}{2} \]
The mass of iron in cell A is 1.5 times that in cell B. Options (A), (B) and (C) come from ignoring the charge on the ion or inverting the ratio.
Step 3: Final Answer:
The ratio is \(3 : 2\), option (D).
Final Answer:
Mass deposited goes as 1/z, so the ratio is 3 to 2. \[ \boxed{\text{(D) }3:2} \]
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