Question

$N{H}_3$ gas is liquefied more easily than $N_2$. Hence:

• A. vander Waals' constants a and b of $N{H}_3$ > that of $N_2$
• B. vander Waals' constants a and b of $N{H}_3$ < that of $N_2$
• C. $a\left(N{H}_3\right)$ > $a\left(N_2\right)$ but $b\left(N{H}_3\right)$ < $b\left(N_2\right)$
• D. $a\left(N{H}_3\right)$ < $a\left(N_2\right)$ but $b\left(N{H}_3\right)$ > $b\left(N_2\right)$

Answer 1

The correct option is C $a\left(N{H}_3\right)$ > $a\left(N_2\right)$ but $b\left(N{H}_3\right)$ < $b\left(N_2\right)$

• In vander Wall's equation of state, the constant 'a' provides a correction for the intermolecular forces. Constant 'b' is a correction for finite molecular size and its value is the volume of one mole of the atoms or molecules.
  
• For a gas which is easily liquifiable value of 'a' will be more and value of 'b' will be less.
• Hence in the question it is given that $N{H}_3$ is liquefied more easilt than $N_2$ and hence $a\left(N{H}_3\right)>a\left(N_2\right)$ but $b\left(N{H}_3\right)<b\left(N_2\right)$.