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 $5.7^{\circ} \mathrm{C}$ 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 ( $-57.0 \mathrm{~kJ} \mathrm{~mol}^{-1}$ ), this experiment could be used to measure the calorimeter constant. In a second experiment (Expt. 2), 100 mL of 2.0 M acetic acid $\left(\mathrm{K}_{\mathrm{a}}=2.0 \times 10^{-5}\right)$ was mixed with 100 mL of 1.0 M NaOH (under identical conditions to Expt. 1) where a temperature rise of $5.6^{\circ} \mathrm{C}$ was measured. (Consider heat capacity of all solutions as $4.2 \mathrm{~J} \mathrm{~g}^{-1} \mathrm{~K}^{-1}$ and density of all solutions as $1.0 \mathrm{~g} \mathrm{~mL}^{-1}$ )

The pH of the solution after Expt. 2 is