1. The problem statement, all variables and given/known data A room with volume 2000 cubic metres has air at T=25degrees Celsius with relative humidity 80%. Density of water vapor in saturated air at 25deg Celsius is 22.8g/m^3. Temperature and pressure of room remains constant. What mass of water vapor must be removed from this air to reduce relative humidity to 50%? 2. Relevant equations relative humidity/100 = water vapor pressure/saturated water pressure 3. The attempt at a solution using above formula and density definition we get (18.3x2000)-(11.4x2000) = 6.9kg. However the textbook answer is double this? Where have I gone wrong?