$3.2$ moles of hydrogen iodide were heated in a sealed bulb at $444\,^{\circ}C$ till the equilibrium was reached. The degree of dissociation of $HI$ at this temperature was found to be $22\%$. The number of moles of hydrogen iodide present at equilibrium are

If $PCl_5$ undergoes $80\%$ dissociation at $250 \, ^\circ C$,what is its vapour density at this temperature?

$A_{(g)} \rightleftharpoons 2B_{(g)} + C_{(g)}$
For the given reaction,if the initial pressure is $450 \ mm \ Hg$ and the total pressure at time $t$ is $720 \ mm \ Hg$ at a constant temperature $T$ and constant volume $V$. The fraction of $A_{(g)}$ decomposed under these conditions is $x \times 10^{-1}$. The value of $x$ is $......$. (nearest integer)

At $STP$,the density of air is $0.001293 \ g \ mL^{-1}$. Its vapour density is $---$.

The degree of dissociation of $PCl_5$ $(\alpha)$ obeying the equilibrium,$PCl_5 \rightleftharpoons PCl_3 + Cl_2$,is approximately related to the pressure at equilibrium by (given $\alpha << 1$):

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?