States of Matter - Result 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 $10 g mol^{-1}$ and $40 g$ $mol^{-1}$ 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 $L=24 cm$, as shown in the figure.

The tube is filled with an inert gas at $1 atm$ pressure and a temperature of $300 K$. Vapours of $X$ and $Y$ react to form a product which is first observed at a distance $d cm$ 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.)

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Solution:

  1. $a$ is the measure of intermolecular force of attraction. Greater the intermolecular force of attraction (H-bond in the present case) higher the value of $a$.


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