Question

The vapour density of undecomposed $N_{2}O_{4}$ is $46$ . When heated, vapour density decreased to $24.5$ due to its dissociation to $NO_{2}$ . The percent dissociation of $N_{2}O_{4}$ at the final temperature is :

• A. $87$
• B. $60$
• C. $40$
• D. $70$

Answer 1

Answer: (A)

$\frac{ \left(\right. normal molar mass \left(\left.\right)_{N_{2} O_{4}}}{ \left(exp . molar mass\right)_{N_{2} O_{4}}}=i$
$i=1+\alpha $
$\frac{ normal molar mass}{ exp . molar mass}=1+\alpha $ (exp. molar mass $=2\times VD$ )
$=2\times 24.5=49$
$\frac{92}{49}=1+\alpha $
$\therefore \alpha =0.87$