you are told to prepare a closed experimental environment (a box) for student mice. The box volume will be 294 liters (about 10 ft3) and the entire air volume will be changed every minute. The relative humidity of the air entering the box is to be controlled at 40% at 21°C. What weight of H2O must be added to the flow of dry air per minute? (Equilibrium vapour pressure for H2O at 21°C ≈ 19 torr). (R = 0.082 liter atm mole–1 deg–1 mol wt: H2O = 18).
