Concentration Equilibrium Constant Expression

Concentration Equilibrium Constant Expression for a Reaction

Reaction Under Consideration

• The specific reaction is as follows:
  • $2 \text{Cu}<em>l(s) + \text{I}</em>2(aq) \rightleftharpoons 2 \text{Cu}^{2+}(aq) + 4 \text{I}^-(aq)$

Concentration Equilibrium Constant (K) Definition

• The concentration equilibrium constant, denoted as $K_{eq}$, quantifies the ratio of the concentrations of the products to the concentrations of the reactants at equilibrium.
• For a generic reaction of the form:
  • $aA + bB \rightleftharpoons cC + dD$
  • The equilibrium constant is expressed as:
  • $K_{eq} = \frac{[C]^c \cdot [D]^d}{[A]^a \cdot [B]^b}$

Application to the Given Reaction

• In the context of the specified reaction, the concentration equilibrium constant expression can be derived as follows:
  • Identifying components:
  • Reactants:
    • ( \text{Cu}_l(s) ) (solid, not included in the expression)
    • ( \text{I}_2(aq) ) (aqueous, included)
  • Products:
    • ( \text{Cu}^{2+}(aq) ) (aqueous, included)
    • ( \text{I}^-(aq) ) (aqueous, included)
  • Writing the expression:
  • Since solids do not appear in equilibrium expressions, the concentration equilibrium constant for this reaction is given by:
  • $K<em>{eq} = \frac{[\text{Cu}^{2+}]^2 \cdot [\text{I}^-]^4}{[\text{I}</em>2]}$

Explanation of Terms

• Aqueous refers to species that are dissolved in water, indicating that their concentration is relevant to the equilibrium state.
• Solid states do not contribute to the equilibrium constant as they have constant concentrations.

Summary

• The final expression for the concentration equilibrium constant for the reaction is:
  • $K<em>{eq} = \frac{[\text{Cu}^{2+}]^2 \cdot [\text{I}^-]^4}{[\text{I}</em>2]}$
• This expression is critical for predicting the behavior of the chemical system at equilibrium and provides insight into the relative concentrations of reactants and products at that state.