How is water vapour a component of air?
Of course, the atmosphere, the air we breathe now is mostly dinitrogen, some dioxygen, (which of course supports respiration), some quantities of carbon dioxide, some inert gases, and SOME water vapour, i.e. gaseous water, and this latter is a function of temperature.
When we collect a gas by water displacement we include
Water vapor is the solute because it is a very small part of the solution that is called the atmosphere.
In a gas gas solution it is somewhat arbitrary to determine which gas is the solute and which gas is the solvent.
However the gas that is the greatest in percentage is usually called the solvent and the smaller gas in terms of percentage is usually called the solute.
Almost 80% of the atmosphere is Nitrogen
Because water vapor is such a small part of the atmosphere it is considered to be the solute not the solvent.