What would the pH of this solution be?

Question

what would be the pH of this solution and why

CaO (s) + H2O (l)  Ca2+ (aq) + 2OH – (aq)

Answer 1

CaO (s) + H2O (l) -->  Ca2+ (aq) + 2OH – (aq)

Clearly, it will be basic, with a pH greater than 7.  I say "clearly" because there are OH- present.  When a solution has more hydroxide ions than it has hydrogen ions the solution is basic.  If a solution had more hydrogen ions than hydroxide ions it would be acidic.

It is impossible to determine the actual numerical value of the pH, other than above 7, because we don't know the amount of CaO dissolved, the volume of water or if the solution is at equilibrium, in other words, saturated.

Calcium hydroxide has a Ksp of 5.5 x 10^-6.

If the solution is saturated then we can determine the actual pH.

Ksp = [Ca2+] [OH-]^2

(x) (2x)^2 = 5.5 x 10^-6

4x^2 = 5.5 x 10^-6

x = (5.5 x 10^-6 / 4)^(1/2) = 0.00117

pOH = -log(0.00117) = 2.93

since pH + pOH = 14, then ...

pH = 11.07

Answer 2

someone at http://chemions.grou.ps  will help you.