Question

Which of the following is true of the solubility product constant?

A. It is the product of the initial concentrations of the ions in a solution.
B. It is an equilibrium constant.
C. It is an equilibrium position.
D. Its value changes in the presence of a common ion.

Answer 1

B ... It's an equilibrium constant that defines the 'extent' of reaction. Caution: Ksp is often used to compare solubility of two salts. This is true only if the ionization ratios of the two salts are identical. If they are not, you'll need to calculate the actual solubility before comparing. For 1:1 ionzn ratio S = SqrRt(Ksp); 2:1 or 1:2 ration S = CubeRt(Ksp/4); 3:1 or 1:3 S = FourthRt(Ksp/27); 4:1 or 1:4 S = FifthRt(Ksp/256) and 2:3 or 3:2 S = FifthRt(Ksp/108).

A is incorrect b/c initial concentrations need to be raised to the power of the respective coefficients in the balanced net ionic equation.

C is incorrect b/c there is no such thing as an 'equilibrium position'

D is incorrect b/c the presence of a common ion only decreases solubility but does not change the Ksp value so long as temperature remains constant.

Answer 2

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