Question

$4.5\, g$ of aluminium (at. mass $27$ amu) is deposited at cathode from a molten electrolyte containing $Al^{3+}$ ions by a certain quantity of electric charge.The volume of hydrogen produced at STP from $H^+$ ions in a solution by the same quantity of electric charge will be

• A. 44.8 L
• B. 11.2 L
• C. 22.4 L
• D. 5.6 L

Answer 1

Answer: (D)

5.6 L

Answer 2

From second law of Faraday
$\frac {m_{AI}}{m_H}= \frac {E_{Al}}{E_H}$
$\frac {4.5}{m_H}= \frac {27/3}{1} \, or \, m_H=0.5 \, g$
$\because$ Volume of $2\, g$ $H_2$ at $STP = 22.4\, L$
$\therefore$ Volume of $0.5\, g$ $H_2$ at STP
\hspace15mm = \frac {22.4 \times 0.5}{2}L=5.6 \, L