The mass of water vapour in a given volume of air is 0.05g at 20oC, while the mass of water vapour required to saturate it at the same temperature is 0.15g....

Answer Details

The relative humidity is the ratio of the actual amount of water vapour present in the air to the maximum amount of water vapour that can be present in the air at a given temperature expressed as a percentage. In this question, the actual amount of water vapour present in the air is given as 0.05g and the mass of water vapour required to saturate it at the same temperature is given as 0.15g. So, the relative humidity can be calculated as: Relative humidity = (actual amount of water vapour/maximum amount of water vapour) x 100% Maximum amount of water vapour is the mass of water vapour required to saturate the air, which is given as 0.15g. Therefore, Relative humidity = (0.05/0.15) x 100% = 33.33% Hence, the relative humidity of the air is 33.33%. Option (c) is the correct answer.