Topic: Atomic and molecular masses, mole concept, molar mass· Some Basic Concepts in Chemistry

Equal moles of hydrogen and oxygen gases are placed in a container with a pin-hole through which both can escape. What fraction of the oxygen escapes in the time required for one-half of the hydrogen to escape ?

1. 1/8

2. 1/4

3. 3/8

4. 1/2

Doubtly Asked 30 Oct 2026 NEET UG 2016 Phase 1 neet Save WhatsApp Report

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Answer: 1. 1/8

Key idea: Graham's law, rate of effusion $\propto 1/\sqrt{M}$.

$$\frac{r_{H_2}}{r_{O_2}}=\sqrt{\frac{32}{2}}=4$$

Both gases start with equal moles and leave the same pin-hole in the same time, so moles escaped are in the ratio of rates. When half of $\mathrm{H_2}$ has escaped, the fraction of $\mathrm{O_2}$ escaped is $\tfrac12\times\tfrac14=\tfrac18$.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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Equal moles of hydrogen and oxygen gases are placed in a container with a pin-hole through which both can escape. What fraction of the oxygen escapes in the time required for one-half of the hydrogen to escape ?

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