Given:
mass of chlorine = 31.5 grams Cl2
temperature of water = 35 degrees C
volume of chlorine = 15 L
*water levels are equal
assume ideal gas behavior
Vapor pressure of water at 35 C = 42.2 torr
To solve for the barometric pressure, use the ideal gas equation:
PV = nRT
where P = Pgas - Pwater
(Pgas - 42.2 torr) * 15 L = 31.5g/70.9g/mol * (35 + 273) K * (760 torr * 22.4 L/298K)
solve for Pgas
Pgas = 563.36 torr
Therefore, the barometric pressure is 563.36 torr.
