Step 1. Calculate the pure water'S pH change value The pure waters hydrogen ion exponent (ph value (pure water)7.00 When add the hydrochloric acid TH=0.01mol/1 liter =0.01mol L-I pH=-og0.01=2.00 △pH=7.00-2.00=5.00( pH unit)Step 1. Calculate the pure water’s pH change value The pure water’s hydrogen ion exponent (pH) value: pH(pure water) = 7.00 When add the hydrochloric acid: [H+ ] = 0.01mol/1 liter =0.01mol.L-1 pH = -log 0.01 = 2.00  pH = 7.00 – 2.00 = 5.00 (pH unit)