At $T \, ^\circ C$,the vapour density of $PCl_5$ is $104.25$. The degree of dissociation of $PCl_5$ is ....$\%$

Consider the following gas phase dissociation, $PCl_{5(g)} \rightleftharpoons PCl_{3(g)} + Cl_{2(g)}$ with equilibrium constant $K_P$ at a particular temperature and at pressure $P$. The degree of dissociation $(\alpha)$ for $PCl_{5(g)}$ is

$A$ $1 \ L$ vessel contains $2 \ moles$ of $PCl_5$ initially. If $K_c$ is found to be $1$,the degree of dissociation of $PCl_5$ for the reaction $PCl_{5(g)} \rightleftharpoons PCl_{3(g)} + Cl_{2(g)}$ is:

If the degree of dissociation for the reaction,$PCl_5 \rightleftharpoons PCl_3 + Cl_2$ is $20\%$ at $1 \ atm$ pressure,calculate $K_c$.

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?

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