Mass $=28 \,g$

$P_i=10 \,atm \quad T_i=57^{\circ} C =330 \,K$

$P_f=5 \,atm \quad T_f=27^{\circ} C =300 \,K$

Volume is kept constant.

$P_i=K \times n_i T_i \quad \dots (i)$

$P_f=K \times n_f T_f \quad \dots (ii)$

Dividing $(i)$ by $(ii)$

$\frac{P_i}{P_f}=\frac{n_i}{n_f} \frac{T_i}{T_f}$

$\frac{n_i}{n_f}=\frac{10}{5} \times \frac{300}{330}$

or $\frac{n_i}{n_f}=2 \times \frac{10}{11}$

$\frac{n_i}{n_f}=\frac{20}{11}$

Now $n_i=1$ mole of $N _2$ $n_f=\frac{11}{20}$ moles

or Mass of $N _2$ left $=\frac{11}{20} \times 28$

$\therefore \text { Quantity released }=28-\frac{11}{20} \times 28$

$=\frac{9}{20} \times 28=\frac{63}{5} g$