Question

Calculate the pH and the pOH of an aqueous solution that is 0.020 M in HCl(aq) and 0.085 M in HBr(aq) at 25 °C.

Answer 1

[H+] = 0.030 + 0.085 = 0.115M
pH = -log(0.115) <<< use a calculator
pOH = 14 - pH <<< just subtract

pH(HCl) = 1.5 => pOH = 12.5
pH(HBr) = 1.1 => pOH = 12.9