Question

A sample of HI(g) is placed in a flask at a pressure of 0.2 atm. At equilibrium the partial pressure of HI(g) is 0.04 atm. What of ${K_P}$ for the given equilibrium?
$2{\text{HI}}({\text{g}}) \rightleftharpoons {{\text{H}}_2}(\;{\text{g}}) + {{\text{I}}_2}(\;{\text{g}})$
A.2
B.4
C.16
D.6

Answer 1

Chemical equilibrium is the condition of a system in which the concentration of the reactant and the concentration of the products do not vary over time and the system's attributes do not change. When a chemical substance in the solid form is in chemical equilibrium with a solution of that substance, it is called solubility equilibrium.

Complete answer: Each gas exerts pressure in a container filled with more than one gas, which is known as partial pressure. The partial pressure of any gas within the container is its pressure. Partial pressure is the pressure exerted by one of the gases in a mixture if it occupies the same volume on its own.
An equilibrium stage is defined as the point where the rate of forward response equals the rate of backward response. The number of reactant molecules changing to products and product molecules turning to reactants is the same at this moment. Chemical equilibrium is dynamic because the same equilibrium may be achieved with the same reactants under identical circumstances everywhere with ongoing molecule exchange. The system achieves chemical equilibrium when the rate of the forward reaction is equal to the rate of the reverse reaction.
Consider,
$2{\text{HI}}({\text{g}}) \rightleftharpoons {{\text{H}}_2}(\;{\text{g}}) + {{\text{I}}_2}(\;{\text{g}})$

| HI| ${H_2}$| ${I_2}$
---|---|---|---
INITIAL| 0.2| 0| 0
CHANGE| -2x| x| x
EQUILIBRIUM| 0.2 – 2x| x| X

But we know that the equilibrium pressure of HI is 0.04 atm. Hence
$0.2 - 2x = 0.04$
Hence, $2x = 0.2 - 0.04 = 0.16$
$\Rightarrow x = 0.08$
We know that
${K_{_p}} = \dfrac{{{P_{{H_2}}}{P_{{I_2}}}}}{{{P_{HI}}}}$
So,
${K_{_p}} = \dfrac{{{P_{{H_2}}}{P_{{I_2}}}}}{{{P_{HI}}}} = \dfrac{{{{(0.08)}^2}}}{{{{(0.04)}^2}}} = \dfrac{{16}}{4}$
$\Rightarrow {K_{_p}} = 4$
Hence option B is the correct answer.

Note:
The solid may dissolve in its entirety, by dissociation, or by chemical reactivity with another solution ingredient, such as acid or alkali. A temperature-dependent solubility product, which acts as an equilibrium constant, characterises each solubility equilibrium. Solubility equilibria are significant in a variety of situations, including pharmaceuticals, the environment, and many others.