Question

Le-Chatelier principle is not applicable to:

• A. $H_2\left(g\right)+I_2\left(g\right)\rightleftharpoons 2HI\left(g\right)$
• B. $Fe\left(s\right)+S\left(s\right)\rightleftharpoons FeS\left(s\right)$
• C. $N_2\left(g\right)+3H_2\left(g\right)\rightleftharpoons 2{NH}_3\left(g\right)$
• D. $N_2\left(g\right)+O_2\left(g\right)\rightleftharpoons 2NO\left(g\right)$

Answer 1

Answer: (B)

$Fe\left(s\right)+S\left(s\right)\rightleftharpoons FeS\left(s\right)$

Le- Chatelier principle is not applicable for solid-solid equilibrium

The activities of pure solids and liquids are equal to 1. Pure solids and liquids are not included in the equilibrium constant expression. This is because they do not affect the reactant amount at equilibrium in the reaction, so they are disregarded and kept at 1, the position of equilibrium would shift to the right. Therefore, adding or removing a solid from a system at equilibrium has no effect on the position of equilibrium.

Le- Chatelier principle is applicable only to gases. But it is not necessary that in a certain chemical reaction, all the reactants species must be in gaseous phase.

$Fe\left(s\right)+S\left(s\right)\rightleftharpoons FeS\left(s\right)$ is in solid equilibrium phase, hence

Le- Chatelier principle is not applicable.