In order to find the concentration of each pH value, we need to use the inverse formula of pH, but now to find the concentration of H3O+, the formula is:
[H3O+] = 10^-pH
For pH 1 we have:
[H3O+] = 10^-6.0
[H3O+] = 1*10^-6
ACIDIC
pH 2:
[H3O+] = 10^-5.5
[H3O+] = 3.16*10^-6
ACIDIC
pH 3:
[H3O+] = 10^-3.2
[H3O+] = 6.31*10^-4
ACIDIC
pH 4:
[H3O+] = 10^-7.2
[H3O+] = 6.31*10^-8
BASIC
