Question

What is the quantity of electricity required to liberate $112 \text{ cm}^3$ of hydrogen gas at STP from acidified water?

• A. $482.5 \text{ C}$
• B. $965 \text{ C}$
• C. $500 \text{ C}$
• D. $96500 \text{ C}$

Hint:

Key: 1 mole gas = 22400 cm$^3$ at STP 1 Faraday = 96500 C

Answer 1

The Correct Option is B

Concept: Electrolysis: \[ 2\text{H}^+ + 2e^- \rightarrow \text{H}_2 \] 1 mole $\text{H}_2$ requires 2 Faraday (2F = 2 × 96500 C)

Step 1: Convert volume to moles. \[ 22400 \text{ cm}^3 = 1 \text{ mole} \] \[ 112 \text{ cm}^3 = \frac{112}{22400} = 0.005 \text{ mole} \]

Step 2: Calculate charge required. \[ 1 \text{ mole H}_2 \rightarrow 2F = 193000 \text{ C} \] \[ 0.005 \text{ mole} \rightarrow 193000 \times 0.005 \] \[ = 965 \text{ C} \]

Step 3: Conclusion.
Thus, required charge = 965 C. Final Answer: Option (B)