GATE 2025 MT – Question 56
Copper is electrodeposited from a CuSO$_4$ bath onto a stainless-steel cathode of total surface area 2 m$^2$. The current density is 200 A m$^{-2}$ and current efficiency is 90%. The mass deposited in 24 h is ______ kg (rounded to two decimal places). Given: $F=96500\ \mathrm{C\,mol^{-1}}$ and copper atomic mass 63.5 g mol$^{-1}$.
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Correct answer: 10.20 to 10.30
Explanation
Total current is $I=jA=200\times2=400$ A. Time is $t=24\times3600=86400$ s, and effective deposition charge is $0.9It$.
Copper deposition uses two electrons per atom. Faraday’s law gives $m=0.9\times400\times86400\times63.5/(2\times96500)$ grams.
Dividing by 1000 gives 10.2339… kg. The answer is **10.23 kg**.