The number of electrons required to deposit 6.35 g of copper at the cathode during the electrolysis of an aqueous solution of copper sulphate will be (Given: Atomic mass of Cu= 63.5 u, NA is Avogadro constant)

# The number of electrons required to deposit 6.35 g of copper at the cathode during the electrolysis of an aqueous solution of copper sulphate will be (Given: Atomic mass of Cu= 63.5 u, NA is Avogadro constant)

1. A

$\left({N}_{\mathrm{A}}/20\right)\mathrm{mol}$

2. B

$\left({N}_{\mathrm{A}}/10\right)\mathrm{mol}$

3. C

$\left({N}_{\mathrm{A}}/5\right)\mathrm{mol}$

4. D

$\left({N}_{\mathrm{A}}/2\right)\mathrm{mol}$

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### Solution:

Amount of Cu to be deposited at the cathode is

Since 2 electrons are required to convert ${\mathrm{Cu}}^{2+}$ ion into Cu, the amount of electrons required to deposit 0.10mol of Cu will be 0.20 mol. The number of electrons required will be (0.20mol) ${N}_{\mathrm{A}}$ i.e. $\left({N}_{\mathrm{A}}/5\right)\mathrm{mol}$.