A lab technician adds 0.015 mol of KOH to 1.00 L of 0.0010 M Ca(NO₃)₂. K_sp = 6.5 × 10^-6 for Ca(OH)₂). Which of the following statements is correct? A) Calcium hydroxide precipitates until the solution is saturated. B) The solution is unsaturated and no precipitate forms. C) The concentration of calcium ions is reduced by the addition of the hydroxide ions. D) One must know K_sp for calcium nitrate to make meaningful predictions on this system. E) The presence of KOH will raise the solubility of Ca(NO₃)₂.

Question

Quizplus · Accepted Answer

The given concentration of Ca(NO₃)₂ (0.0010 M) is less than the solubility product constant (K_sp) of calcium hydroxide (6.5 × 10^-6), which indicates that the solution is unsaturated and no precipitate of calcium hydroxide will form. The addition of KOH will increase the concentration of hydroxide ions, but this will not affect the solubility of calcium hydroxide, as it is a sparingly soluble salt. The given information is sufficient to make this prediction without the need for the solubility product constant of calcium nitrate. The option stating that calcium hydroxide will precipitate until the solution is saturated is incorrect, as the solution at the given concentration of calcium nitrate is unsaturated. The option that the concentration of calcium ions will be reduced by the addition of KOH is also incorrect, as both calcium and hydroxide ions will be present in the solution.

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