A soft drink was bottled with a partial pressure of ${\mathrm{CO}}_2$ of 3 bar over the liquid at room temperature. The partial pressure of ${\mathrm{CO}}_2$ over the solution approaches a value of 30 bar when $44 \mathrm{g}$ of ${\mathrm{CO}}_2$ is dissolved in $1 \mathrm{kg}$ of water at room temperature. The approximate $\mathrm{pH}$ of the soft drink is ___________$\times {10}^{-1}$.
(First dissociation constant of ${\mathrm{H}}_2{\mathrm{CO}}_3=4.0\times {10}^{-7}; \log 2=0.3;$ density of the soft drink $=1 \mathrm{g} {\mathrm{mL}}^{-1}$)