Question

How can I calculate solubility of calcium hydroxide?

Answer 1

You use the solubility product constant to calculate the solubility of a sparingly soluble electrolyte like calcium hydroxide.

This question is like the one at

http://socratic.org/questions/how-can-i-calculate-the-molar-solubility-of-baso4-given-a-ksp-of-1-07-10-10?source=search

The solubility product constant for Ca(OH)₂ is 5.5 × 10⁻⁶.

The balanced chemical equation is

Ca(OH)₂(s) ⇌ Ca²⁺(aq) + 2OH⁻(aq)
I/mol·L⁻¹: -; 0; 0
C/mol·L⁻¹: -; +`x`; +`2x`
E/mol·L⁻¹: -; `x`; `2x`

`K_"sp"` = [Ca²⁺][ OH⁻]² = `x × (2x)^2 = 4x^3` = 5.5 × 10⁻⁶

`x^3` = 1.375 × 10⁻⁶ (2 significant figures + 2 guard digits)

`x` = ∛(1.375 ×10⁻⁶) = 1.1 × 10⁻²

Solubility = `x` mol/L = 1.1 × 10⁻² mol/L = 0.011 mol/L