12-3 Flashcards
What is a closed system?
One that matter cannot get in or out of but Energy Can.
What is Equilibrium?
The dynamic condition in which 2 opposing changes occur at equal rates in the same closer system.
Define theoretical construct.
No system can be completely closed but we can come close.
Define what a phase is.
Any part of a system with uniform composition and properties.
Ex: a flask of water with a stopper in it is a liquid/ vapor closed system. Here, the 2 phases are liquid and vapor.
What molecules evaporate the fastest and gain energy?
Water molecules at the surface can gain energy and escape the surface (evaporate)
What are water molecules below the surface held in place by?
Water molecules below the surface are held in place by surrounding water molecules… surface molecules aren’t held at the surface so they evaporate now easily.
When will equilibrium be established?
If temperature remains constant, there will be a point where the amount of evaporating will equal the amount condensing.
What happens to some of the molecules that escape?
Lose energy and return to the surface of the liquid (condense)
What will be constant at equilibrium?
The relative amounts of liquid and vapor will be constant…not necessarily equal.
When will the amount evaporating be equal to the amount condensing?
At equilibrium.
What is the equation for evaporation?
Liquid + Heat nrg –> Vapor
What is the equation for condensation?
Vapor + Liq + Nrg
What is the best way to write a equilibrium expression?
Liq + Heat Vapor
In Le Chatlier’s Principle when a system at equilibrium is disturbed by a stress, what happens?
a new equilibrium point will win established that will be minimize the stress.
Stress is a change in what for Le Chartlier?
For Le Chartlier, stress is a change in P, T, or V of a container.
What does EVP stand for?
Equilibrium Vapor Pressure
Define EVP
The pressure exerted by a vapor that is at equilibrium with it’s liquid
eg: pushing stopper off
What happens when the T of the liquid increases?
If the T of the liquid increases, more liquid molecules will gain enough KE to escape from the surface of the liquid.
What causes EVP to change?
Temperature of a liquid causes vapor pressure to increase, exerting a higher EVP. A new equilibrium point will be established with more vapor and less liquid. Therefore, EVP changes with T.
Define volatile liquids and give examples.
Evaporate quickly b/c of weak attraction between molecules.
ex: ether, ammonia, perfume.
Define nonvolatile liquids and give examples.
Evaporate slowly b/c of strong attraction between molecules.
ex: water, oil.
Define Molar Heat of Vaporization.
Amount of energy needed go vaporize 1 mol of a liquid at it’s boiling point.
What are the effects of T change?
Add nrg and rxn is “pushed fwd from left to right so more vapor at a new equilibrium point; also less liq.
What are the effects of P change?
An increase in P will push the rxn equilibrium to the left. A decrease will push rxn to the right.
