12-3

Question 0

What is a closed system?

Answer 0

One that matter cannot get in or out of but Energy Can.

Question 1

What is Equilibrium?

Answer 1

The dynamic condition in which 2 opposing changes occur at equal rates in the same closer system.

Question 2

Define theoretical construct.

Answer 2

No system can be completely closed but we can come close.

Question 3

Define what a phase is.

Answer 3

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.

Question 4

What molecules evaporate the fastest and gain energy?

Answer 4

Water molecules at the surface can gain energy and escape the surface (evaporate)

Question 5

What are water molecules below the surface held in place by?

Answer 5

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.

Question 6

When will equilibrium be established?

Answer 6

If temperature remains constant, there will be a point where the amount of evaporating will equal the amount condensing.

Question 7

What happens to some of the molecules that escape?

Answer 7

Lose energy and return to the surface of the liquid (condense)

Question 8

What will be constant at equilibrium?

Answer 8

The relative amounts of liquid and vapor will be constant…not necessarily equal.

Question 9

When will the amount evaporating be equal to the amount condensing?

Answer 9

At equilibrium.

Question 10

What is the equation for evaporation?

Answer 10

Liquid + Heat nrg –> Vapor

Question 11

What is the equation for condensation?

Answer 11

Vapor + Liq + Nrg

Question 12

What is the best way to write a equilibrium expression?

Answer 12

Liq + Heat Vapor

Question 13

In Le Chatlier’s Principle when a system at equilibrium is disturbed by a stress, what happens?

Answer 13

a new equilibrium point will win established that will be minimize the stress.

Question 14

Stress is a change in what for Le Chartlier?

Answer 14

For Le Chartlier, stress is a change in P, T, or V of a container.

Question 15

What does EVP stand for?

Answer 15

Equilibrium Vapor Pressure

Question 16

Define EVP

Answer 16

The pressure exerted by a vapor that is at equilibrium with it’s liquid

eg: pushing stopper off

Question 17

What happens when the T of the liquid increases?

Answer 17

If the T of the liquid increases, more liquid molecules will gain enough KE to escape from the surface of the liquid.

Question 18

What causes EVP to change?

Answer 18

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.

Question 19

Define volatile liquids and give examples.

Answer 19

Evaporate quickly b/c of weak attraction between molecules.

ex: ether, ammonia, perfume.

Question 20

Define nonvolatile liquids and give examples.

Answer 20

Evaporate slowly b/c of strong attraction between molecules.

ex: water, oil.

Question 21

Define Molar Heat of Vaporization.

Answer 21

Amount of energy needed go vaporize 1 mol of a liquid at it’s boiling point.

Question 22

What are the effects of T change?

Answer 22

Add nrg and rxn is “pushed fwd from left to right so more vapor at a new equilibrium point; also less liq.

Question 23

What are the effects of P change?

Answer 23

An increase in P will push the rxn equilibrium to the left. A decrease will push rxn to the right.

Question 24

What are the effects of V change?

Answer 24

The same as pressure changes. When the volume of the system is decreed P increases & vice versa.

Question 25

Define boiling.

Answer 25

Defined as the change of a liquid to a vapor within the liq as well as the surface.

Question 26

When does boiling occur?

Answer 26

Occurs when EVP = Atmosphere P… at a certain place and time.