Question

Calculate the pH of the given solution: 0.3 g of Ca(OH)₂ dissolved in water to give 500 mL of solution.

Answer 1

For 0.3 g of Ca(OH)2 melted in water to give 500 mL of solvent:

Ca(OH)2  →   Ca2+ + 2OH-

[Ca(OH)2]  = 0.3x1000/500 = 0.6M

OH-(aq) = 2 x [Ca(OH)2(aq)] = 2 x 0.6 = 1.2M

[H+]  = Kw  /  OH-(aq)

= 10-14/1.2 M

= 0.833 x 10-14

pH  =  -log(0.833 x 10-14)

= -log(8.33 x 10-13)

= (-0.902 + 13)

= 12.098