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 $S_{8}to{S}_2$ . Find the $K_p$ for reaction :$S_8\left(g\right)\iff 4S_2\left(g\right)$

• A. 2.55(atm)${}^3$
• B. 5.25atm${}^3$
• C. 2.55(atm)${}^2$
• D. 0.255(atm)${}^3$

Answer 1

Answer: (A)

2.55(atm)${}^3$

The equilibrium reaction is $S_8\left(g\right)\iff 4S_2\left(g\right)$.

	$S_8$	$S_2$
Initial pressures	1	0
Equilibrium pressures	$1-0.29=0.71$	$4\times 0.29$

The expression for the equilibrium constant is $K_p=\frac{(P_{S_2}{)}^4}{P_{S_8}}=\frac{(4\times 2.9{)}^4}{0.71}=2.55at{m}^3$.