$NO_{(g)} + \frac{1}{2}{O_2} \rightleftharpoons N{O_2}_{(g)}$
$2N{O_2}_{(g)} \rightleftharpoons 2NO_{(g)} + {O_2}_{(g)}$
$X :\, 2SO_{2(g)} + O_{2(g)} $ $\rightleftharpoons$ $ 2SO_{3(g)}$
$Y:\, PCl_{5(g)} $ $\rightleftharpoons$ $ PCl_{3(g)} + Cl_{2(g)}$
$Z :\, 2HI_{(g)} $ $\rightleftharpoons$ $ H_{2(g)} + I_{2(g)}$