Which one of the following will change the value of an equilibrium constant?

(A) varying the initial concentrations of reactants

(B) changing the volume of the reaction vessel

(C) varying the initial concentrations of products

(D) adding other substances that do not react with any of the species involved in the equilibrium

(E) changing temperature

(E) changing temperature

Explanation:

Consider the following reversible balanced reaction:

aA+bB⇋cC+dD

If we know the molar concentrations of each of the reaction species, we can find the value of Kc using the relationship:

Kc = ([C]^c * [D]^d) / ([A]^a * [B]^b)

where:

[C] and [D] are the concentrations of the products in the equilibrium; [A] and [B] reagent concentrations in equilibrium; already; b; c and d are the stoichiometric coefficients of the balanced equation. Concentrations are commonly expressed in molarity, which has units of moles / 1

There are some important things to remember when calculating Kc:

- Kc is a constant for a specific reaction at a specific temperature. If you change the reaction temperature, then Kc also changes

- Pure solids and liquids, including solvents, are not considered for equilibrium expression.

- The reaction must be balanced with the written coefficients as the minimum possible integer value in order to obtain the correct value of Kc