Equilibrium Concentrations Calculation with Kc = 0.20

What are the final equilibrium concentrations for HA, H, and A⁻ given Kc = 0.20?

How can we determine the equilibrium concentrations of the substances involved in the reaction when the equilibrium constant Kc is given as 0.20?

Final Answer:

To find the final equilibrium concentrations for HA, H+, and A-, set up an equilibrium expression with Kc = [H+][A-]/[HA] and solve for x using the initial concentration of HA and assuming initially there is no A-. Exact equilibrium concentrations cannot be provided without additional information or approximations.

Explanation: To find the final equilibrium concentrations for HA, H+, and A−, we must set up an equilibrium expression using the given acid dissociation constant (Kc) and the initial concentrations of the substances involved. For example, the equilibrium constant Kc = 0.20 for a hypothetical reaction HA ⇌ H+ + A− can be expressed as Kc = [H+][A−]/[HA]. If we assume that the initial concentration of HA is 0.2 M and there is no A− initially, we can designate x as the change in concentration for H+ and A− and (0.2 - x) for the change in concentration of HA at equilibrium. So, the equilibrium expression would be: 0.20 = (x)(x)/(0.2 - x). Solving for x involves quadratics, where x represents both [H+] and [A−], and (0.2 - x) represents [HA]. Since exact values are not provided for initial concentrations nor is there specific information about the approximate value of x compare to 0.2, we cannot give the specific numerical values of equilibrium concentrations without making approximations or additional assumptions.