Question

Assertion : HCl diffuses faster than ammonia.
Reason : Rate of diffusion of a gas is inversely proportional to the square root of its density.

• A. Both assertion and reason are correct and reason is the correct explanation of the assertion.
• B. Both assertion and reason are correct, but reason is not the correct explanation of the assertion.
• C. Assertion is correct, but reason is incorrect.
• D. Assertion is incorrect, but reason is correct.
• E. Both assertion and reason are incorrect.

Answer 1

Answer: (D)

Assertion is incorrect, but reason is correct.

According to Graham's law,

Rate of effusion

$\left(r\right)\propto \sqrt{\frac{1}{d}}=k\sqrt{\frac{1}{d}}(d=density)$

$\frac{r_{N{H}_3}}{r_{HCl}}=\sqrt{\frac{d_{HCl}}{d_{N{H}_3}}}=\sqrt{\frac{M_{HCl}}{M_{N{H}_3}}}$

$(\therefore d=Mass/volume)$

$\sqrt{\frac{M_{HCl}}{M_{N{H}_3}}}=\sqrt{\frac{36.5}{17}}=1.46$

Therefore, ammonia will diffuse 1.46 times faster than hydrogen chloride gas. Therefore, lighter gases diffuse faster than the denser gases.