$4 \ mol$ of $PCl_5$ is heated in a closed vessel at a constant temperature. If the degree of dissociation for $PCl_5$ is $0.5$,what will be the total number of moles at equilibrium?

For which of the following reactions,the degree of dissociation cannot be calculated from the vapour density data?
$I. \ 2HI_{(g)} \rightleftharpoons H_{2(g)} + I_{2(g)}$
$II. \ 2NH_{3(g)} \rightleftharpoons N_{2(g)} + 3H_{2(g)}$
$III. \ 2NO_{(g)} \rightleftharpoons N_{2(g)} + O_{2(g)}$
$IV. \ PCl_{5(g)} \rightleftharpoons PCl_{3(g)} + Cl_{2(g)}$

For the reaction $A \rightleftharpoons \frac{1}{2} B + C$,the degree of dissociation $\alpha$ in terms of vapour density $D_t$ (theoretical) and $D_o$ (observed) is given by:

The vapour density of a mixture containing $NO_2$ and $N_2O_4$ is $27.6$. The mole fraction of $N_2O_4$ in the mixture is

For the reaction $P \rightleftharpoons Q + R$,initially $2 \, \text{mol}$ of $P$ is taken. At equilibrium,$0.5 \, \text{mol}$ of $P$ dissociates. The degree of dissociation will be ...... .

The equation $\alpha = \frac{D - d}{(n - 1)d}$ represents the degree of dissociation. For which of the following reactions is this equation valid,where $D$ is the theoretical vapour density and $d$ is the observed vapour density?