A solution is prepared by adding 4.50 mol of sodium hydroxide to 1.00 L of 1.00 M Co(NO₃)₂. What is the equilibrium concentration of cobalt ions? K_f= 5.0 × 10⁹ for Co(OH)₄²⁻ A)1.1 × 10 ⁻² M B)1.4 × 10 ⁻⁵ M C)3.2 × 10 ⁻⁹ M D)2.0 × 10 ⁻¹⁰ M E)4.9 × 10 ⁻¹³ M

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Quizplus · Accepted Answer

The equilibrium constant (Kf) for the formation of Co(OH)4^- from Co2+ and OH^- is given as 5.0 × 10^19. When 4.50 mol of NaOH is added to 1.00 L of 1.00 M Co(NO3)2, the initial concentration of OH^- will be 4.50 M. The reaction will proceed until the equilibrium is established according to the Kf value. Since Kf is very large, it indicates that the reaction proceeds almost to completion, forming Co(OH)4^- and consuming Co2+ and OH^- ions. The equilibrium concentration of Co2+ ions can be calculated using the stoichiometry of the reaction and the Kf value, leading to a very low concentration of cobalt ions, consistent with the choice that indicates a concentration of 3.2 × 10^-19 M.

A Solution Is Prepared by Adding 4