States of Matter 1 Question 90
90. At room temperature, ammonia gas at $1 \mathrm{~atm}$ pressure and hydrogen chloride gas at $p$ atm pressure are allowed to effuse through identical pin holes from opposite ends of a glass tube of one metre length and of uniform cross-section.
Ammonium chloride is first formed at a distance of $60 \mathrm{~cm}$ from the end through which $\mathrm{HCl}$ gas is sent in. What is the value of $p$ ?
$(1982,4 \mathrm{M})$
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Solution:
- Rate of effusion $(r) \propto \frac{p}{\sqrt{M}}$
$$ \begin{array}{rlrl} \Rightarrow & & \frac{r\left(\mathrm{NH}_{3}\right)}{r(\mathrm{HCl})} & =\frac{1}{\sqrt{17}} \times \frac{\sqrt{36.5}}{p} \Rightarrow \ \Rightarrow & p & =\frac{3}{2} \sqrt{\frac{36.5}{17}}=2.20 \mathrm{~atm} \end{array} $$
