Question

At a certain temperature the value of the equilibrium constant, Kc, is 1.27 for the reaction. 2As (s) + 3H2 (g) ⇌ 2AsH3 (g) What is the value of Kc for the following reaction? AsH3 (g) ⇌ As (s) + 3/2H2 (g)

Answer 1

Answer:

$0.887$

Explanation:

Hello,

In this case, the law of mass action for the first reaction turns out:

$Kc=\frac{[AsH_3]^2}{[As]^2[H_2] ^3}=1.27$

Now, for the second reaction is:

$Kc=\frac{[As][H_2] ^{3/2}}{[AsH_3]}$

Therefore, by applying square root for the first reaction, one obtains:

$\sqrt{Kc} =\sqrt{\frac{[AsH_3]^2}{[As]^2[H_2] ^3}} =\sqrt{1.27}$

$\frac{\sqrt{[AsH_3]^2} }{\sqrt{[As]^2} \sqrt{[H_2] ^3} } =\sqrt{1.27}$

$\sqrt{1.27}=\frac{[AsH_3]}{[As][H_2] ^{3/2}}$

Finally, since Kc is asked for the inverse reaction, one modifies the previous equation as:

$Kc'=\frac{1}{\sqrt{1.27} }=\frac{[As][H_2] ^{3/2}}{[AsH_3]}=0.887$

Best regards.