When 100 mL of 1.0 M HCl was mixed with 100 mL of 1.0 M NaOH in an...

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 ${5.7}^{o}C$ 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 $( - 57.0kJmo{l}^{- 1} )$ , this experiment could be used to measure the calorimeter constant. In a second experiment (Expt. 2), 100 mL of 2.0 M acetic acid $( {K}_{a} = 2.0 \times {10}^{- 5} )$ was mixed with 100 mL of 1.0 M NaOH (under identical conditions to Expt. 1) where a temperature rise of ${5.6}^{o}C$ was measured. (Consider heat capacity of all solutions as $4.2J{g}^{- 1}{K}^{- 1}$ and density of all solutions as $1.0gm{L}^{- 1}$ )
The pH of the solution after Expt. 2 is