A solution is prepared by mixing 50.0 mL of 0.50 M Cu(NO₃)₂with 50.0 mL of 0.50 M Co(NO₃)₂. Sodium hydroxide is added to the mixture. Which hydroxide precipitates first and what concentration of hydroxide ions present in solution will accomplish the separation? K_sp = 2.2 × 10⁻²⁰ for Cu(OH)₂, K_sp = 1.3 × 10⁻¹⁵for Co(OH)₂ A)Co(OH)₂; [OH ⁻] = 6.9 × 10 ⁻⁶ M B)Co(OH)₂; [OH ⁻] = 2.6 × 10 ⁻⁷ M C)Cu(OH)₂; [OH ⁻] = 1.8 × 10 ⁻⁷ M D)Cu(OH)₂; [OH ⁻] = 1.1 × 10 ⁻⁹ M E)Cu(OH)₂; [OH ⁻] = 1.0 × 10 ⁻¹⁷ M

Question

Quizplus · Accepted Answer

The correct answer is D because the Ksp value for Cu(OH)2 is smaller than that for Co(OH)2, indicating that Cu(OH)2 is less soluble and will precipitate first. The concentration of hydroxide ions required to precipitate Cu(OH)2 can be calculated using the Ksp expression:Ksp = [Cu2+][OH-]22.2 × 10^-20 = [Cu2+][OH-]2[OH-] = 1.1 × 10^-9 M

A Solution Is Prepared by Mixing 50