First of all, the answer has 3 places of accuracy.
The formula for pH is
pH = - log[H+]
Given: Ph = 3.20
Solution
3.20 = - log[H+]
Divide by - 1
-3.20 = log[H+]
Take the antilog of both sides
10^-3.20 = [H+]
[H+]= 6.30 * 10^-4 moles/L This is a measure of concentration.
It can also be written as 0.000630 moles/L
