Question

When sulphur (in the form of $S_8$) is heated at temperature $T$, at equilibrium, the pressure of $S_8$ falls by $30\%$ from $1.0atm$, because $S_8\left(g\right)$ is partially converted into $S_2\left(g\right).$
Find the value of $K_p$ for this reaction $S_8\left(g\right)\rightleftharpoons 4S_2\left(g\right)$.

• A. $2.96$
• B. $6.14$
• C. $4.28$
• D. None of these

Answer 1

The correct option is A $2.96$

$S_8\left(g\right)\rightleftharpoons 4S_2\left(g\right)$
$\text{Initial pressure}1atm0$
$\text{At Eqm}(1-0.3)(4\times 0.3)$
$=0.7atm=1.2atm$

$K_p=\frac{P_{S_2}^4\left(g\right)}{P_{S_8\left(g\right)}}{K}_p=\frac{(1.2{)}^4}{0.70}=2.96$