pH of solution

Consider that:

• In a closed system, only 10% of the $\ce{CO2}$ dissolves into the water.
• Before was 1 mol of $\ce{CO2}$ and 1 liter of $\ce{H2O}$ .
• Considering the complete ionization as a function of H + and $\ce{H2CO3}$ , and its two steps.
• The ionization constant is $5.0 \times 10^{-7} \text{ mol / L}$ .

What is the pH of this solution?