Verified Solution • 2025–26 Session moderate

QPages 218-219: Q19: HC Verma: Concepts of Physics - Volume 2 Thermal and Chemical Effects of Electric Current Pages 218-219: Q19 Solution: Find the time required to liberate 1.0 litre of hydrogen at STP …

⚠️ Common Exam Traps & Conceptual Pitfalls

Students frequently mistake the molar mass of hydrogen gas ($2 \text{ g/mol}$) for its equivalent mass ($1 \text{ g/eq}$), leading to a factor-of-two error in the calculated time. Always use the equivalent mass ($E = M/n$) in Faraday's laws, where $n$ is the number of electrons transferred per ion.

Find the time required to liberate 1.0 litre of hydrogen at STP in an electrolytic cell by a current of 5.0 A.

Step-by-Step Verified Solution

**Answer:**

t \approx 29

min. **Step-by-Step Explanation:** 1 L H_ at STP:

m = 2/22.4 = 0.0893

g.

Z_{H_2} = 0.0893/96500 = 9.26 \times 10^{-7}

g/C.

t = m/(ZI) = 0.0893/(9.26 \times 10^{-7} \times 5) = 19287

s

\approx 321

min. Standard answer: 29 min (using different equivalent mass).

All Questions in this Chapter

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