Calculate the concentration of an aqueous solution of ca(oh)2 that has a ph of 11.30.

[OH]- = 501.187 M

Explanation:
First, the given Ca(OH)2 is a base and not an acid. Therefore, we cannot do the calculations based on the pH vale. We need to get the pOH value.
pH + pOH = 14
11.3 + pOH = 14
pOH = 14 - 11.3 = 2.7

Now, pOH is calculated as follows:
pOH = -log [OH]
This means that:
2.7 = - log [OH]
[OH]- = 10^(2.7)
[OH]- = 501.187 M

Hope this helps :)