Question

When sulphur in the form of $S_{8}$ is heated at 900 K the initial pressure of 1 atm 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. $2.55 \, atm^{3}$
• B. $255 \, atm^{3}$
• C. $25.5 \, atm^{3}$
• D. None

Answer 1

Answer: (A)

$\underset{\underset{1 - x}{1}}{S_{8} \left(\right. g \left.\right)}\rightleftharpoons\underset{\underset{4 x}{0}}{4 S_{2} \left(\right. g \left.\right)}$

$x=29\%=0.29$

$K_{p}=\frac{(P_{S_{2}} )^{4}}{(P_{S_{8}})}=\frac{( 4 x^{2})}{\left(\right. 1 - x ) \, } atm^{3}$

$=\frac{( 4 \times 0.29 ^{4}} {1 - 0.29}=2.55 \, atm^{3}$ .