States of Matter 1 Question 49
49. Statement I The value of van der Waals’ constant ’ $a$ ’ is larger for ammonia than for nitrogen.
Statement II Hydrogen bonding is present in ammonia.
(1998)
Passage Based Questions
Passage
$X$ and $Y$ are two volatile liquids with molar weights of $10 \mathrm{~g} \mathrm{~mol}^{-1}$ and $40 \mathrm{~g}$ $\mathrm{mol}^{-1}$ respectively. Two cotton plugs, one soaked in $X$ and
the other soaked in $Y$, are simultaneously placed at the ends of a tube of length $L=24 \mathrm{~cm}$, as shown in the figure.
The tube is filled with an inert gas at $1 \mathrm{~atm}$ pressure and a temperature of $300 \mathrm{~K}$. Vapours of $X$ and $Y$ react to form a product which is first observed at a distance $d \mathrm{~cm}$ from the plug soaked in $X$. Take $X$ and $Y$ to have equal molecular diameters and assume ideal behaviour for the inert gas and the two vapours.
(2014 Adv.)
Show Answer
Solution:
- $a$ is the measure of intermolecular force of attraction. Greater the intermolecular force of attraction (H-bond in the present case) higher the value of $a$.
