3-13. The solubility of carbon dioxide (CO₂) in water under standard conditions is 1.45 g/L (partial CO₂ pressure 1 atm). Assuming that air contains 0.039% of CO₂, calculate the pH of water exposed to the air at standard conditions

3-15. Piperidine (0.5 mmol) and formic acid (0.5 mmol) were mixed with 1 L of water. The pH of the resultant solution was adjusted to 7.5. Calculate the fractions of protonated piperidine and deprotonated formic acid in the resultant solution.