Practice question · Match the pairs

Match each salt formula type to its relation between solubility product and molar solubility.

AB, such as silver chloride
$\mathrm{AB_2}$ , such as calcium fluoride
$\mathrm{A_3B}$ , such as silver phosphate
Any pure solid phase

$K_{sp} = 4s^3$
$K_{sp} = 27s^4$
Omitted from the expression entirely
$K_{sp} = s^2$

Hints

Raise each ion concentration to its own coefficient and multiply.
For A3B the first ion is at 3s and is cubed, giving 27 s to the fourth.

Show the answer

AB, such as silver chloride → $K_{sp} = s^2$
$\mathrm{AB_2}$ , such as calcium fluoride → $K_{sp} = 4s^3$
$\mathrm{A_3B}$ , such as silver phosphate → $K_{sp} = 27s^4$
Any pure solid phase → Omitted from the expression entirely

Why

Each ion appears at its stoichiometric multiple of $s$ and raised to its coefficient, which is where the numerical prefactors 4 and 27 come from. Pure solids never appear, since their concentration cannot vary.

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Match each salt formula type to its relation between solubility product and molar solubility.

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