In the reaction SO2 (g) + H2O (l) ↔ H2SO3 (aq), with K = 2.1 × 10–3, the concentration of SO2 is 0.35 M, and the concentration of H2SO3 is 0.23 M. This reaction _______. A. is in equilibrium B. must shift to the reactants to be in equilibrium C. must shift to the products to be in equilibrium D. must have the pressure increased to reach equilibrium E. None of the Above

Reaction quotient (Q) : It is defined as the measurement of the relative amounts of products and reactants present during a reaction at a particular time.

The given balanced chemical reaction is,

[tex]SO_2(g)+H_2O(l)\rightarrow H_2SO_3(aq)[/tex]

The expression for reaction quotient will be :

[tex]Q=\frac{[H_2SO_3(aq)]}{[SO_2(g)]}[/tex]

In this expression, only gaseous or aqueous states are includes and pure liquid or solid states are omitted.

Now put all the given values in this expression, we get

[tex]Q=\frac{0.23}{(0.35)}=0.657[/tex]

The given equilibrium constant value is, [tex]K=2.1\times 10^{-3}[/tex]

Equilibrium constant : It is defined as the equilibrium constant. It is defined as the ratio of concentration of products to the concentration of reactants.

There are 3 conditions:

When [tex]Q>K[/tex] that means product > reactant. So, the reaction is reactant favored.

When [tex]Q<K[/tex] that means reactant > product. So, the reaction is product favored.

When [tex]Q=K[/tex] that means product = reactant. So, the reaction is in equilibrium.

From the above we conclude that, the [tex]Q>K[/tex] that means product > reactant. So, the reaction is reactant favored that means reaction must shift to the reactants to be in equilibrium.

Hence, the correct option is, (B) must shift to the reactants to be in equilibrium.