Model a soft drink as a solution of water with CO₂ dissolved at 298.15 K. In this way we ignore the sugar, flavor, and color. The Henry’s law constant for CO₂ at 298.15 K is 0.035 (mol/kg-bar).

(a) What pH and composition exist when the vapor phase is 3.5 bar absolute at room temperature ignoring O₂ or N₂ present? This approximates conditions in the unopened container.

(b) After the soft drink is opened, and the liquid equilibrates with atmosphere, what pH and composition exist when the CO₂ vapor mole fraction is y_CO2 = 0.0003 (the normal ambient value) and the pressure is 1 bar?