Is humidity percentage an indication of thew amount of water in the air?

Question

That is to say at 70% humidity is 70% of an arbitrary unit of volume of air water and 30% other gases? If so would 100% humidity be pure water?

Answer 1

No.Given a quantity of dry air, for a particular temperature,there is definitely a maximum amount of water vapour which the air can hold.If the amount reaches maximum,the relative humidity will be 100 percent for that particular temperature.But if the temperature of the air increases,the amount of water vapour,it can hold will also increase.On the other hand, if the temperature increases without any addition of water vapour,the relative humidity will come down from 100 percent.So, the same amount of water vapour may indicate 100 percent at a lower temperature and  may show 90 percent at a  higher temperature.Hence the relative humidity is not an indication of the amount of water vapour in air.

Water vapour is only constituent of air which is constantly changing.It may constitute at the most one percent of the total volume of air.If the humidity is 70 percent ,this percentage comes under the one percent of the total volume of air.So,other gases will always be approximately 99 percent of the total volume of air.

Answer 2

Humidity is the ratio of how much water vapor is in the air compared to how much water vapor the air could hold before it hits 100% (water vapor turns to liquid). The temperature the air must be for the vapor to turn to liquid is called the dew point.   Hot air can hold more water vapor than cold air because it's less dense. Therefore, the temperature must drop for the dew point to be reached.

Answer 3

No.  It is a mathimatical representation of a quantity.  70% represents 7/10th of the amount of water as a gas a volume of air can contain at that temperature.  That volume of air can hold another 3/10th and then would be 100%.  It has mostly nothing to do with the other gasses.  And yes, all water when it is in the form of a gas is pure.  H20 by definition is pure whether liquid, solid, or a gas.