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 solubility product constant for Ca(OH)2 is given (Ksp = 6.5 x 10^-6), which allows us to calculate the maximum concentration of Ca2+ and OH- ions that can coexist in solution without precipitating. Since the initial concentration of Ca2+ ions (0.0010 M) is much smaller than this maximum concentration, the solution is unsaturated and no precipitate forms. The presence of KOH does not affect the solubility of Ca(OH)2 in this case. The concentration of calcium ions is not significantly reduced by the addition of a small amount of hydroxide ions. Information about the solubility product constant of calcium nitrate is not required to predict the outcome of this system.

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