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Science Clinic => Chemistry => Topic started by: meagbuch on Nov 18, 2019

Title: Explain the common ion effect with respect to molar solubility.
Post by: meagbuch on Nov 18, 2019

Question 1

Consider the Ksp values for two compounds: MZ, Ksp = 1.5 × 10-20 and MZ2, Ksp = 1.5 × 10-20. Why don't these compounds have the same molar solubility?

Question 2

Explain the common ion effect with respect to molar solubility.

Title: Explain the common ion effect with respect to molar solubility.
Post by: jomama on Nov 18, 2019

Answer 1

These two compounds have the same solubility product constant, but that does not mean they have the same molar solubilities. Since the first compound contains two ions and the second compound contains three ions, their solubility product expressions differ and therefore their molar solubilities must differ. Compound MZ2 will have a higher molar solubility.

Answer 2

The common ion effect occurs when a solubility equilibrium is shifted due to a second compound that contains an ion common with the first. For example, the molar solubility of MA (MA ⇌ M+ + A-) would be higher in pure water than if MA were dissolved in an aqueous solution that already contained another compound with A-.