chapter 13: equilibrium

Question 1

what conditions must be met in order for a reaction to occur?

Answer 1

1) the reacting entities must collide
2) the entities must be oriented so that bonds can be rearranged to form products
3) the reacting entities have enough energy to overcome the Ea barrier

Question 2

what factors affect reaction rates?

Answer 2

1) nature of reactants ( simple vs. complex molecular structure)
2) temperature (rate increases with a temp increase because the collision rate increases)
3) concentration (aqueous system)
4) pressure (gaseous systems), by changing volume
5) surface area (solid states)

Question 3

when is a reaction at equilibrium?

Answer 3

when the amounts of reactants and products stop changing with time

Question 4

what is homogenous equilibrium?

Answer 4

reactants and products are in the same phase

Question 5

what is heterogeneous equilibrium?

Answer 5

reactants and products are in 2 different phases

Question 6

what conditions apply to any system at equilibrium?

Answer 6

1) the rates of the forward and reverse reactions are equal
2) the observable macroscopic properties don’t change
3) the system is closed with no exchange of matter or energy with the surrounding environment
4) the equilibrium can be approached from either direction

Question 7

what is equilibrium?

Answer 7

macroscopically static and dynamic

Question 8

what does the value of the equilibrium constant depend on?

Answer 8

the system under examination and the temperature

Question 9

what do not occur in the equilibrium law expression?

Answer 9

solid and pure liquids

Question 10

what way does the reaction shift is k > 1?

Answer 10

to the right

Question 11

what way does the reaction shift if k< 1?

Answer 11

to the left

Question 12

what way does the reaction shift is k = 1?

Answer 12

no shift

Question 13

what communicates an equilibrium exists?

Answer 13

equilibrium arrows, but they do not communicate what extent the equilibrium occurs

Question 14

what does percent yield show?

Answer 14

the percent yield of an equilibrium reaction can communicate the extent of the reaction

Question 15

how do you calculate percent yield?

Answer 15

percent yield = [equilibrium]/[maximum] x 100%

Question 16

what way does the reaction shift is % yield is <50%?

Answer 16

left

Question 17

what way does the reaction shift if % yield is > 50%?

Answer 17

right

Question 18

what happens in % yield is > 99%?

Answer 18

it is stoich value, so only the forward arrow is necessary

Question 19

what happens if % yield is <1%

Answer 19

the reaction is non-spontaneous

Question 20

how can you express the extent of the reaction qualitatively?

Answer 20

when you don’t have numeric values, you can express the extent to which products or reactants are favoured with bolded arrows

Question 21

what is the relationship between K and Kp?

Answer 21

Kp = K(RT)^deltaN

Question 22

what is Q - reaction quotient used for?

Answer 22

initial concentration

Question 23

what is K used for?

Answer 23

equilibrium concentrations

Question 24

what if Q = K?

Answer 24

the system is at equilibrium, no shift will occur

Question 25

what if Q>K?

Answer 25

the system shifts to the left

Question 26

what if Q

Answer 26

the system shifts to the right

Question 27

what is le chatelier’s principle?

Answer 27

when subjected to a stress, a dynamic equilibrium responds in such a way as to relieve the stress and return to a new state of equilibrium

Question 28

what is the only factor that can change K?

Answer 28

temperature