When 100 mL of 1.0 M HCl was mixed with 100mL of 1.0 M NaOH in an insulated beaker at constant pressure, a temperature increase of 5.7°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 $\left(-57.0kJmo{l}^{-1}\right)$ , this experiment could be used to measure the calorimeter constant. 

In a second experiment (Expt. 2), 100 mL of 2.0 M acetic acid $\left(K_a=2.0\times {10}^{-5}\right)$  was mixed with 100mL of 1.0 M NaOH(under identical conditions to Expt.1)  where a temperature rise of 5.6°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