The negative Zn pole of a Daniell cell, sending a constant current through a circuit, decreases in mass by 0.13 g in 30 minutes. If the electrochemical equivalents of Zn and Cu are 32.5 and 31.5 respectively, the increase in the mass of the positive Cu pole in this time is (a) 0.180 g (b) 0.141 g (c) 0.126 g (d) 0.242 g

Answer: (c). Same current, same time, so same charge: m = Zq ⇒ m ∝ Z. mCu = 0.13 × (31.5)/(32.5) ≈ 0.126 g So the answer is (c).

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Electrical Power & Heating Effect

The negative $\text{Zn}$ pole of a Daniell cell, sending a constant current through a circuit, decreases in mass by $0.13\text{ g}$ in $30$ minutes. If the electrochemical equivalents of $\text{Zn}$ and $\text{Cu}$ are $32.5$ and $31.5$ respectively, the increase in the mass of the positive $\text{Cu}$ pole in this time is

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Answer: (c)

Same current, same time, so same charge: $m = Zq \Rightarrow m \propto Z$ .
$m_{Cu} = 0.13 \times \frac{31.5}{32.5} \approx 0.126$ g
So the answer is (c).

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