Estimate the mole fraction of CO2 in water at 0.7 MPa total pressure and 298.15 K.

Carbon dioxide solubility in water plays a critical role in biological physiology and environmental ocean chemistry, affects the accuracy of acid-base titrations in analytical chemistry, and makes many beverages fizzy. The Henry’s law constant for CO₂ in water is listed on the NIST Chemistry WebBook^a as K_H = 0.035 mol/kg-bar at 298.15 K. Estimate the mole fraction of CO₂ in water at 0.7 MPa total pressure and 298.15 K. Treat the vapor phase as an ideal gas and the liquid as an ideal solution with the Henry’s law standard state. Neglect formation of ionic carbonate species.