Calculate the NaOH concentration necessary to precipitate Ca(OH)₂ from a solution in which [Ca²⁺] = 1.0. K_sp of Ca(OH)₂ = 8 x 10^-6.

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The chemical equation for the precipitation reaction is: Ca²⁺ + 2 NaOH → Ca(OH)₂ + Na2²⁺ The reaction consumes 2 moles of NaOH for every mole of Ca²⁺ that is precipitated. Therefore, we need to find the concentration of NaOH that corresponds to a Ca²⁺ concentration of 1.0 M. First, we need to calculate the ion product of Ca(OH)₂, which is: Qsp = [Ca²⁺][OH-]2 At equilibrium, Qsp = Ksp, so: Ksp = [Ca(OH)₂] = 8 x 10^-6 Substituting the given Ca²⁺ concentration and solving for [OH-], we get: 8 x 10^-6 = (1.0 M)[OH-]2 [OH-] = sqrt(8 x 10^-6) = 8 x 10^-4 M Since we need 2 moles of NaOH for every mole of Ca²⁺, the required concentration of NaOH is: 2(1.0 M)(8 x 10^-4) = 1.6 x 10^-3 M Therefore, the best choice is B, 2.8 x 10^-3 M, which is the closest option to the calculated value.

Calculate the NaOH Concentration Necessary to Precipitate Ca(OH)2 from a Solution

Calculate the NaOH Concentration Necessary to Precipitate Ca(OH)₂ from a Solution