Respuesta :
The ph of a saturated solution of Ca(OH)2 is 12.35
CALCULATION:
For the reaction
Ca(OH)2 → Ca2+ + 2OH-
we will use the Ksp expression to solve for the concentration [OH-] and then use the acid base concepts to get the pH:
Ksp = [Ca2+][OH-]^2
The listed Ksp value is 5.5 x 10^-6. Substituting this to the Ksp expression, we have
Ksp = 5.5 x 10^-6 = (s) (2s)^2 = 4s^3
s3 = 5.5x10^-6 / 4
Taking the cube root, we now have
s = cube root of (5.5x10^-6 / 4)s
= 0.01112
We know that the value of [OH-] is actually equal to 2s:
[OH-] = 2s = 2 * 0.01112 = 0.02224 M
We can now calculate for pOH:
pOH = - log [OH-]
= -log(0.02224)
= 1.65
Therefore, the pH is
pH = 14 - pOH
= 14 - 1.65
= 12.35
CALCULATION:
For the reaction
Ca(OH)2 → Ca2+ + 2OH-
we will use the Ksp expression to solve for the concentration [OH-] and then use the acid base concepts to get the pH:
Ksp = [Ca2+][OH-]^2
The listed Ksp value is 5.5 x 10^-6. Substituting this to the Ksp expression, we have
Ksp = 5.5 x 10^-6 = (s) (2s)^2 = 4s^3
s3 = 5.5x10^-6 / 4
Taking the cube root, we now have
s = cube root of (5.5x10^-6 / 4)s
= 0.01112
We know that the value of [OH-] is actually equal to 2s:
[OH-] = 2s = 2 * 0.01112 = 0.02224 M
We can now calculate for pOH:
pOH = - log [OH-]
= -log(0.02224)
= 1.65
Therefore, the pH is
pH = 14 - pOH
= 14 - 1.65
= 12.35
The pH of the solution of calcium hydroxide is 12.3
From that standard tables, we know that the Ksp of Ca(OH)2 is 5.5 x 10^-6. Recall, that the Ksp is obtained from;
Ca(OH)2(s) ⇄ Ca^2+(aq) + 2OH^-(aq)
Hence;
Ksp = s * (2s)^2
Ksp = 4s^3
s = ∛Ksp/4
s = ∛5.5 x 10^-6/4
s= 0.01 M
But [OH^-] = 2s
[OH^-] = 2(0.01 M)
[OH^-] = 0.02 M
pOH = - log(0.02 M)
pOH = 1.7
pH = 14 - 1.7 = 12.3
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