Do humans exhale water vapor

Answer 1

Yes, the air leaving the lungs has accumulated some of the moisture on the alveolar surfaces (inside of the lungs), this leaves with the exhaled air, making it more humid (more water vapour) than inhaled air.

Aside from this and the higher temperature of exhaled air, it is pretty similar to that being inhaled. The concentrations of carbon dioxide and oxygen have altered also, more carbon dioxide leaves than enters, and more oxygen enters than leaves. This is due to removing carbon dioxide from the blood and taking in oxygen to remove metabolic waste and fuel metabolic processes respectively.

Note that not all the oxygen inhaled is absorbed into the blood, and that the exhaled air contains other gases found naturally in the air such as minute proportions of the noble gases and nitrogen.