GATE 2019 MT – Question 56
100 metric tons of copper concentrate containing 21 wt% Cu must be processed in six months, each with 25 working days and 8 h/day. After acid leaching, copper is deposited in 10 series cells. Find minimum current per cell in amperes (nearest integer), using F=96500 C per gram equivalent and Cu atomic weight 63. Assume complete recovery and current efficiency.
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Correct answer: 1485 to 1495
Explanation
Total copper is 21000 kg, or 2100 kg per cell over the full schedule. Time is 6×25×8×3600=4.32×10⁶ s. Copper deposition requires 2F per mole, so $I=[(2.1\times10^6/63)(2)(96500)]/(4.32\times10^6)=1489.2$ A. Series cells all carry this same current. The source’s “per month” wording describes the processing schedule; amperes are already charge per second.