What is the vapour density of $O_2$ gas?

Given is a concentrated solution of a weak electrolyte $A_{x}B_{y}$ of concentration '$c$' and dissociation constant '$K$'. The degree of dissociation is given by:

At temperature,$T$,a compound $AB_{2(g)}$ dissociates according to the reaction; $2AB_{2(g)} \rightleftharpoons 2AB_{(g)} + B_{2(g)}$ with a degree of dissociation $x$,which is small compared with unity. The expression for $K_p$,in terms of $x$ and the total pressure,$P$ is

For the reaction,$N_2 + O_2 \rightleftharpoons 2NO$,the equilibrium constant is $K_c = 2$. If both reactants have the same initial moles,what is the degree of dissociation of $N_2$ and $O_2$?

$2SO_3 \rightleftharpoons 2SO_2 + O_2$. Initially,$3$ moles of $SO_3$ were heated. If the degree of dissociation of $SO_3$ is $40\%$,find the total number of moles at equilibrium.

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