Part A Calculate the concentration of an aqueous solution of

Part A

Calculate the concentration of an aqueous solution of Ca(OH)2 that has a pH of 11.29.

Express your answer using two significant figures.

Solution

Ca(OH)2 ---> Ca(2+) + 2 OH(-)

In any actual solution pH+pOH = 14
In this case 11.29+pOH = 14
pOH = 2.71

But pOH = -log[OH-]
log[OH-] = -pOH = -2.71
[OH-] = 10^(-2.71) = 0.00195

But from the ionization reaction you can see that each mole of Ca(OH)2 gives 2 moles of OH-
So. the concentration of Ca(OH)2 is half that of OH-, or 0.0039 M