Question

An acidic solution of $C{u}^{2+}$ salt containing 0.4 g of $C{u}^{2+}$ is electrolysed until all $Cu$ is deposited. The electrolysis is continued for seven more minutes with the volume of solution kept at 100 ml and the current at 1.2 A. Calculate the volume of gases evolved at NTP during entire electrolysis.

Atomic mass of $Cu$ = $63.6$ g/mol.

• A. 2.2 liters
• B. 4.8 liters
  
• C. 4.0 liters
  
• D. None of these
  

Answer 1

Answer: (D)

None of these

At anode: $4O{H}^{-}\to O_2\left(g\right)+2H_{2}O+2e^{-}$

At cathode: $2H_{2}O+2e^{-}\to H_2\left(g\right)+2O{H}^{-}$

Volume of $O_2$ liberated in 7 minutes$=\frac{It{V}_e}{96500}=\frac{1.2\times 7\times 60\times 22.4}{96500\times 4}=0.029litres$

Volume of $H_2$ liberated in 7 minutes$=\frac{It{V}_e}{96500}=\frac{1.2\times 7\times 60\times 22.4}{96500\times 2}=0.058litres$

Moles of $O_2$ produce during the reduction of Cu ion $=\frac{n_{Cu}}{2}=\frac{0.4}{63.6\times 2}=0.00314mol$

$\therefore$ Total volume of gas $=0.029+0.058+0.00314\times 22.4=0.157L$