An acidic solution of dichromate is electrolyzed for 8 minutes using 2A current. As per the following equation
\(\mathrm{Cr_2O_7^{2-} + 14H^+ + 6e^- \to 2Cr^{3+} + 7H_2O}\)
The amount of \(\mathrm{Cr^{3+}}\) obtained was 0.104 g. The efficiency of the process (in %) is (Take : F = 96000 C, At. mass of chromium = 52) ______.
\(\mathrm{Cr_2O_7^{2-} + 14H^+ + 6e^- \to 2Cr^{3+} + 7H_2O}\)
The amount of \(\mathrm{Cr^{3+}}\) obtained was 0.104 g. The efficiency of the process (in %) is (Take : F = 96000 C, At. mass of chromium = 52) ______.
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Correct Answer: 60
Solution and Explanation
Moles of electrons = \(\frac{960}{96000} = 0.01\) mol.
From the equation, 6 mol e- give 2 mol \(\mathrm{Cr^{3+}}\), i.e. 3 mol e- per mol \(\mathrm{Cr^{3+}}\).
Theoretical moles of \(\mathrm{Cr^{3+}}\) = \(\frac{0.01}{3}\) mol.
Theoretical mass = \(\frac{0.01}{3} \times 52 = 0.1733\) g.
Efficiency = \(\frac{0.104}{0.1733} \times 100 = 60\%\).
Answer: 60
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