Weight of 1 m³ of humid air as compared to 1 m³ of dry air, under the same conditions, is

ANS:A - less

I apologize for the confusion. Let me correct that. The weight of 1 m^3 of humid air compared to 1 m^3 of dry air under the same conditions is less. When air is humid, it contains water vapor molecules in addition to the usual nitrogen, oxygen, and other gases. However, water vapor molecules are lighter than the molecules of the major components of dry air (nitrogen and oxygen). Therefore, for a given volume of humid air, the overall weight of the mixture is less than that of an equal volume of dry air because the water vapor molecules contribute less to the overall weight than the molecules of nitrogen and oxygen would in dry air. So, humid air would weigh less per unit volume compared to an equal volume of dry air under the same conditions.