(adsbygoogle = window.adsbygoogle || []).push({}); 69. Calculate the Ksp for each of the salts whose solubility is listed below.

a) CaSO4 = 3.3 x 10-3 mol/L

b) MgF2 = 2.7 x 10-3 mol/L

Answers:

a) Solution

1. Write the dissociation reaction and the Ksp expression for the equilibrium reaction. Thus,

CaSO4(s) <---> Ca2+ (aq) + SO42- (aq)

Ksp = [Ca2+][SO42-]

2. Calculate the concentrations of the ions at equilibrium from the stoichiometric information provided in the equilibrium equation. The equation shows that 1 mol of CaSO4 produces 1 mol of Ca2+ and 1 mol of SO42- at equilibrium. Therefore,

[Ca2+] = 3.3 x 10-3 mol/L

[ SO42-] = 3.3 x 10-3 mol/L

3. Substitute the concentrations into the Ksp expression:

Ksp = (3.3 x 10-3)( 3.3 x 10-3)

= 1.2 x 10-5

b) MgF2 <---> Mg2+ (aq) + F22+ (aq)

Ksp = [Mg2+][F22+]

[Mg2+] = 2.7 x 10-3

[F22+] = 2.7 x 10-3

Ksp = (2.7 x 10-3)(2.7 x 10-3)

= 7.3 x 10-6

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# Homework Help: Calculating Ksp of salt (answer check)

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