Question

When sulphur in the form of $S_8$ is heated at $900K$, the initial pressure of one $atm$ of $S_{\left(8\right)}$ falls by 29% at equilibrium. This is because of conversion of some $S_8$ to $S_2.$ Find the value of equilibrium constant for this reaction.

• A. $1.16$
• B. $0.71$
• C. $2.55$
• D. $5.1$

Answer 1

The correct option is C $2.55$

According to the given Reaction,
$\begin{array}{cccc}& S_8\left(g\right)& \rightleftharpoons & 4S_2\left(g\right)\\ Atstart& 1& & 0\\ Ateqbm& 1-0.29& & 4\times 0.29\\ & =0.71atm& & =1.16atm\end{array}$

$K_p=\frac{[p{S}_2{]}^4}{\left[p{S}_8\right]}$

putting the values,
$K_p=\frac{(1.16{)}^4}{\left(0.71\right)}=2.55$