Arrange H2O, H2S, and CH4 in order from lowest to highest vapor pressure?

Question

anonymous · Answer

CH4 < H2S < H2O

aaronq · Answer

the other way around, $H_2O$ has the lowest VP

ookawaiioo · Answer

Tinybookworm is correct!!!!!

aaronq · Answer

lol nah.. Vapour pressure is the pressure exerted by the vapour over a liquid/solid in a closed container. It's related to the boiling point, such that a substance with a higher BP will have a lower VP.

You can agree that if you had two closed containers, one with a mole of water and one with a mole of methane, at room temperature and 1 atm pressure. Most (if not all) of the methane (BP -164 celsius) would be in the gas phase while most of the water would still be liquid (if you don't know why this is so, review the effects of intermolecular forces on physical characteristics). If there are more particles in the gas phase than in the liquid phase there are more collisions with the walls of the container and, therefore, it's vapour (gas) pressure is higher. 

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In conclusion, i'm right.