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A saturated solution of calcium hydroxide has a hydroxide-ion concentration of 0.025M. What is the pH of the solution?

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Final answer:

The pH of the solution is 2.05.

Step-by-step explanation:

We begin by determining [OH¯]. The concentration of the solute is 0.0044 M, but because Ca(OH)₂ is a strong base, there are two OH ions in solution for every formula unit dissolved, so the actual [OH-] is two times this:

[OH-] = 2 × 0.0044 M = 0.0088 M

Now we can use the Kw expression:

Kw = [H3O+][OH-]

Since water is neutral, the concentration of [H3O+] is equal to the concentration of [OH-]. Therefore, we have:

[OH-] = [H3O+] = 0.0088 M

The pH of a solution is calculated using the equation pH = -log[H3O+]. Plugging in the given concentration:

pH = -log(0.0088) = 2.05

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