Equilibrium and Rates

Question 1

rates measure…

Answer 1

the speed of any change that occurs over an interval of time

Question 2

collision theory

Answer 2

• particles must collide in order for reactions to occur

2 factors:
1. frequency of collisions (high # needed for reaction to occur)
2. effectiveness of collisions (particles collide at proper angles with enough energy)

Question 3

activation energy

Answer 3

Ea
energy needed to start a reaction

Question 4

heat of reaction

Answer 4

ΔHrxn
energy released or absorbed
products - reactants

Question 5

potential energy

Answer 5

PE

Question 6

activated complex

Answer 6

short lived species formed after molecules collide

Question 7

factors affecting reaction rate

Answer 7

1. temp
2. concentration of reactants (pressure for gases)
3. particle size
4. catalysts

Question 8

factors affecting reaction rate (specific)

Answer 8

1. increase temp, increase rate
2. increase concentration, increase rate (inc pressure, inc rate)
3. decrease particle size, increase rate
4. catalysts increase rate, lower activation energy

Question 9

reversible reactions

Answer 9

example:
2SO2(g) + O2(g) → 2SO3(g)
2SO3(g) → 2SO2(g) + O2(g)

both reactions happen at the same time

Question 10

forward rxn

Answer 10

left to right (reactants to products)

Question 11

reverse rxn

Answer 11

right to left (products to reactants)

Question 12

chemical equilibrium

Answer 12

state where forward and reverse reactions take place at the same rate

NOTE
- concentrations are constant, but not necessarily same

Question 13

A —-> <- B

Answer 13

“top arrow is longer”
- favors formation of PRODUCTS
- higher concentration of products

Question 14

la chatelier’s principle

Answer 14

if stress is applied to a system at equilibrium, system changes to relieve the stress
(new equilibrium is established)

Question 15

stress

Answer 15

a change that disturbs the equilibrium

Question 16

types of stress

Answer 16

1. change in concentration
2. change in temperature
3. change in pressure

Question 17

A + B -><- C + D + heat

Answer 17

exothermic reaction
- heat is product
- equilibrium shifts right/towards products

Question 18

A + B + heat -><- C + D

Answer 18

endothermic reaction
- heat is reactant
- equilibrium shifts left/towards reactants

Question 19

change in pressuer

Answer 19

• affects substances in gas phase only
• pressure exerted by a gas is directly proportional to the # of molecules/moles

2 moles of gas exert twice as much pressure as 1 mole of gas

Question 20

pressure effect

Answer 20

• increase P, shifts right, fewer molecules
• decrease P, shifts left, more molecules

Question 21

effect of catalyst

Answer 21

• favor neither reaction in an equilibrium system
• causes reactions to reach equilibrium faster
• does not cause stress

Question 22

Keq

Answer 22

products/reactants

([C]^c * [D]^d) / ([A]^a * [B]^b

Question 23

Keq

Answer 23

• if larger than 1, products r favored
• if 1, neither favored
• if smaller than 1, reactants r favored

Question 24

Keq depends on

Answer 24

temperature

Question 25

“favored”

Answer 25

that side of the equation has higher number of moles and higher concentrations than the other side

Question 26

not included in equilibrium expression:

Answer 26

solids and pure liquids

• only gas and aq