Question

When $S$ in the form of $S_8$ is heated at $900K$, the initial pressure of 1 atmosphere falls by 29% at equilibrium. This is because of conversion of some $S_8\left(g\right)$ to $S_2\left(g\right)$. The $K_p$ for reaction is x. Then 100x is_________.

Answer 1

$S_8\left(g\right)\rightleftharpoons 4S_2\left(g\right)$
Initial pressure $10$
Final pressure at equilibrium $(1-0.29)4\times 0.29$
$\because K_p=\frac{{\left[P_{S_2}^{\prime }\right]}^4}{\left[P_{S_8}^{\prime }\right]}=\frac{{(4\times 0.29)}^4}{0.71}=2.55{atm}^3$