When 100 mL of 1.0 M HCl was mixed with 100 mL of 1.0 M NaOH in an insulated beaker at…

When 100 mL of 1.0 M HCl was mixed with 100 mL of 1.0 M NaOH in an insulated beaker at constant pressure, a temperature increase of 5.7 ^oC was measured for the beaker and its contents (Expt. 1). Because the enthalpy of neutralization of a strong acid with a strong base is a constant (–57.0 kJ mol^–1), this experiment could be used to measure the calorimeter constant. In a second experiment (Expt.2), 100 mL of 2.0 M acetic acid (K_a = 2.0 x 10^–5) was mixed with 100 mL of 1.0 M NaOH (under identical conditions to Expt.1) where a temperature rise of 5.6 ^oC was measured.
(Consider heat capacity of all solutions as 4.2 J g^–1 K^–1 and density of all solutions as 1.0 g mL^–1)
The pH of the solution after Expt.2 is (2015)