Consider the reaction: Fe3+ (aq) + SCN- (aq) ⇌ FeSCN2+ (aq). A solution is made containing an initial [Fe3+] of 1.0*10^-3 M and an initial [SCN-] of 8.0*10^-4 M. At equilibrium, [FeSCN2+] = 1.7*10^-4 M. Calculate the value of the equilibrium constant (Kc).

Verified step by step guidance

1. Identify the initial concentrations of the reactants: [Fe^{3+}]_0 = 1.0 \times 10^{-3} \text{ M} and [SCN^-]_0 = 8.0 \times 10^{-4} \text{ M}.
2. Determine the change in concentration for the formation of FeSCN^{2+} at equilibrium, which is given as [FeSCN^{2+}] = 1.7 \times 10^{-4} \text{ M}.
3. Calculate the equilibrium concentrations of the reactants: [Fe^{3+}]_{eq} = [Fe^{3+}]_0 - [FeSCN^{2+}] and [SCN^-]_{eq} = [SCN^-]_0 - [FeSCN^{2+}].
4. Write the expression for the equilibrium constant K_c: K_c = \frac{[FeSCN^{2+}]_{eq}}{[Fe^{3+}]_{eq} \times [SCN^-]_{eq}}.
5. Substitute the equilibrium concentrations into the K_c expression to find the value of the equilibrium constant.

Key Concepts

Equilibrium Constant (Kc)

The equilibrium constant (Kc) is a numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium for a given reaction at a specific temperature. It is calculated using the formula Kc = [products]^[coefficients] / [reactants]^[coefficients]. A larger Kc indicates a greater concentration of products at equilibrium, while a smaller Kc suggests that reactants are favored.

ICE Table

An ICE table (Initial, Change, Equilibrium) is a tool used to organize the concentrations of reactants and products in a chemical reaction at different stages. It helps in determining the changes in concentration as the reaction progresses towards equilibrium. By filling in the initial concentrations, the changes that occur, and the equilibrium concentrations, one can easily calculate the equilibrium constant.

Le Chatelier's Principle

Le Chatelier's Principle states that if a dynamic equilibrium is disturbed by changing the conditions, the system will adjust itself to counteract the change and restore a new equilibrium. This principle is crucial for understanding how changes in concentration, pressure, or temperature can affect the position of equilibrium and the value of the equilibrium constant.