Question

Hydrogen chloride gas is sent into a $100$ metre tube from one end $A$ and ammonia gas from the other end $B$ under similar conditions. The distance from $A$ where the two gases meet is:

• A. $40.48$ metres from the end $A$
• B. $43$ metres from the end $A$
• C. $42.48$ metres from the end $A$
• D. $43.48$ metres from the end $A$

Answer 1

Answer: (A)

$40.48$ metres from the end $A$

Rate of diffusion = $\frac{1}{\sqrt{M}}$

$\therefore r_{HCl}:r_{N{H}_3}=\frac{1}{\sqrt{36.5}}:\frac{1}{\sqrt{17}}$

$=\sqrt{\frac{2}{73}}:\frac{1}{\sqrt{17}}$

$=\frac{r_{HCl}}{r_{N{H}_3}}=\sqrt{\frac{34}{73}}$

$=\frac{x}{100-x}=\sqrt{\frac{34}{73}}$ [$\because$ distance is directly proportional to rate]

$=x=40.48$

Therefore, the correct option is A.