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Question
The same amount of electricity was passed through two separate electrolytic cells containing solutions of nickel nitrate and chromium nitrate respectively. If 2.935 g of Ni was deposited in the first cell. The amount of Cr deposited in the another cell?
Given: molar mass of Nickel and chromium are 58.74 and 52 gm−1 respectively.
Solution
\[\ce{Ni^{2+}_{( aq)} + 2e^- -> Ni_{(s)}}\]
\[\ce{Cr^{2+}_{( aq)} + 3e^- -> Cr_{(s)}}\]
The above reaction indicates that a 2F charge is required to deposit 58.7 g of Nickel from nickel nitrate and 3F charge is required to deposit 52 g of chromium.
Given that 2.935 gram of Nickel is deposited
∴ The amount of charge passed through the cell = `(2"F")/(58.7 "g") xx 2.935 "g"`
= 0.1F
∴ If 0.1F charge is passed through chromium nitrate the amount of chromium deposited
= `(52 "g")/(3"F") xx 0.1"F"`
= 1.733 g
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