Question

Calcium hydroxide is partially soluble as shown by the

following reaction:
Ca(OH)2(s) → Ca2+ (aq) + 20H(aq)
What is the pOH of a 5 x 10-5 M Ca(OH)2 solution?
pH = __
Enter the answer

Answer 1

4

10

Step-by-step explanation:

The reaction equation is given as;

Ca(OH)₂ → Ca²⁺ + 2OH⁻

Concentration of Ca(OH)₂ = 5 x 10⁻⁵M

Unknown:

pOH of the solution = ?

pH of the solution = ?

Solution:

Solve for the pOH of this solution using the expression below obtained from the ionic product of water;

pOH = ⁻log₁₀[OH⁻]

Ca(OH)₂ → Ca²⁺ + 2OH⁻

1moldm⁻³ 1moldm⁻³ 2 x 1moldm⁻³

5 x 10⁻⁵moldm⁻³ 5 x 10⁻⁵moldm⁻³ 2( 5 x 10⁻⁵moldm⁻³ )

1 x 10⁻⁴moldm⁻³

Therefore;

pOH = -log₁₀ 1 x 10⁻⁴ = 4

Since

pOH + pH = 14

pH = 14 - 4 = 10