what is liquid-vapor equilibrium? Like when you leave a water bottle in the sun and there is condensation around the water bottle and on the bottom of the cap, how does that happen if it's hot and not cold, don't you need to cool to condense?

Question

preetha · Answer

Short answer: Yes. 
Long explanation: the molecules of a liquid are held together by stronger forces of attraction than in a gas.  But at the surface of a liquid, the molecules are only held down on one side (below the surface) so every now and then, the molecules at the surface manage to escape.  If you cover the surface of a container with liquid, the molecules of liquid will slowly escape to gas.  Then after some time, some of the molecules of gas will get lower in energy and condense back to liquid.  Over time you have an equilibrium with molecules going to gas and coming back.  This is the equilibrium condition.  It influencedd by the strength of the force of attraction between the molecules in the liquid.

anonymous · Answer

does that mean the pressure in the bottle goes up?

preetha · Answer

Yes.  IF you start with an open bottle, with a liquid. Then cap it.  Then over time the pressue of the vapor/gas in the open space will increase, till equilibrium is reached.  So the pressure is more than it was open.

anonymous · Answer

Okay this is in one of my chem worksheets. How does the concentration of the gas once equilibrium is reached compare to that when the volume of the gas was half as great? I guess it could be any gas in general.

preetha · Answer

So, if I understand this correctly.  You start with volume V/2.  Then change that to V.  The conentration will ....? Think about it and tell me.  Greater volume means ...

anonymous · Answer

is concentration pressure? like the concentration of molecules. if so, then I would say the concentration would increase if the volume was half as great

preetha · Answer

Yes.  Pressure and concentration are directly proportional.  As V decreases, pressure will increase.  Conentration which is number o fmolecules /volume will increase.

anonymous · Answer

K. I think that is it for right now. We just started on the unit for equilibrium

preetha · Answer

Good luck.