A lab technician adds 0.015 mol of KOH to 1.00 L of 0.0010 M Ca(NO3)2. Ksp = 6.5

ID: 508753 • Letter: A

Question

A lab technician adds 0.015 mol of KOH to 1.00 L of 0.0010 M Ca(NO3)2. Ksp = 6.5 10-6 for Ca(OH)2. Which of the following statements is correct?

a. The presence of KOH will raise the solubility of Ca(NO3)2.

b. The solution is unsaturated and no precipitate forms.

c. One must know Ksp for calcium nitrate to make meaningful predictions on this system.

d. The concentration of calcium ions is reduced by the addition of the hydroxide ions.

e. Calcium hydroxide precipitates until the solution is saturated.

KOH (aq.) ----------> K+ (aq.) + OH- (aq.)

[OH-] = 0.015 M

Ca(NO3)2 (aq.) --------> Ca2+ (aq.) + 2 NO3- (aq.)

[Ca2+] = 0.0010 M

Ca(OH)2 (s) = Ca2+ (aq.) + 2 OH- (aq.)

Q = [Ca2+][OH-]2

Q = (0.0010)(0.015)2

Q = 2.25 * 10-7 M3

Since Q < Ksp (= 6.5*10-6),

(b) The solution is unsaturated and no precipitation forms.

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