Construct the expression for Kc for the following reaction 4HCl(aq) + O2(g) = 2H2O(0) + 2Cl2(g )
The Correct Answer and Explanation is :
To construct the equilibrium constant expression ( K_c ) for the reaction:
[ 4 \text{HCl} (aq) + \text{O}_2 (g) \rightleftharpoons 2 \text{H}_2\text{O} (l) + 2 \text{Cl}_2 (g) ]
we follow the guidelines for writing the equilibrium constant expression based on the stoichiometry of the balanced chemical equation.
Expression for ( K_c )
The equilibrium constant ( K_c ) is defined as the ratio of the concentration of products to the concentration of reactants, each raised to the power of their respective coefficients in the balanced equation.
For the reaction given:
[
K_c = \frac{[\text{H}_2\text{O}]^2 [\text{Cl}_2]^2}{[\text{HCl}]^4 [\text{O}_2]}
]
Explanation
- Understanding ( K_c ): The equilibrium constant ( K_c ) quantifies the ratio of the concentration of products to reactants at equilibrium. It indicates how far a reaction proceeds toward products under specific conditions.
- Coefficients and Concentrations: Each term in the expression corresponds to a species involved in the reaction. The concentrations of gaseous and aqueous species are included, while the concentrations of solids and liquids are omitted from the expression. In this reaction, (\text{H}_2\text{O}) is a liquid, so it is not included in the ( K_c ) expression. The concentrations are expressed in terms of molarity (moles per liter).
- Applying Stoichiometry: The coefficients in the balanced equation are crucial. For example, since there are 2 moles of (\text{H}_2\text{O}) produced, its concentration is squared. Similarly, the concentration of (\text{Cl}_2) is squared, and the concentrations of (\text{HCl}) and (\text{O}_2) are raised to the fourth and first power, respectively, based on their coefficients.
- Equilibrium Considerations: At equilibrium, the concentrations of reactants and products remain constant, and this expression allows chemists to calculate the ratio of these concentrations, predicting the position of equilibrium for various conditions.
In summary, the expression for ( K_c ) provides insights into the dynamics of the reaction and the favorability of product formation under equilibrium conditions.