Question

An acidic solution of $Cu^{2+}$ containing $0.4\, g$ of $Cu^{2+}$ ions is electrolysed until all the copper is deposited. What is the volume of oxygen evolved at $NTP$ ?

• A. $141\, cc$
• B. $31.75\, cc$
• C. $64\, cc$
• D. $32\, cc$

Answer 1

Answer: (A)

$141\, cc$

Answer 2

$H_{2}O \to2H^{+}+\frac{1}{2} O_{2}+2e^{-}\quad$ (Oxidation)
$Cu^{2+}+2e^{-} \to Cu\quad$ (Reduction)
$Cu^{2+}+H_{2}O\to Cu+2H^{+} +\frac{1}{2} O_{2}$
$\frac{63.5}{2}=31.75\,g$ of $Cu^{2+}\equiv\frac{1}{2}\times 22400=11200\,cc$ of $O_{2}$
$31.75\,g$ of $Cu^{2+}$ evolve $11200 \,cc$ of $O_{2}$ at $NTP$
$0.4\,g$ of $Cu^{2+}$ will evolve $\frac{11200}{31.75}\times 0.4=141\,cc$ of $O_{2}$

So, the correct option is (A): 141 cc.