Question

What is the pH of a solution that has a hydroxide ion concentration of 0.80×10−10 M?Express your answer to two significant figures.

Answer 1

We have

hydroxide ion concentration

[OH^-] = 0.80 $\times$ 10^-10 M

Now we know the formulas

pOH = -log[OH^-]

and pH + pOH = 14

So

pOH = -log[OH^-] = -log(0.80 $\times$ 10^-10) = 10.09

Now

pH + pOH = 14

then

pH = 14 - pOH = 14 - 10.09 = 3.9

So our answer is

pH = 3.9