5.1.2 equilibrium

Question 1

what is homogeneous equilibrium?

Answer 1

an equilibrium in which all the species making up the reactants and products have the same physical state

Question 2

what is heterogeneous equilibrium?

Answer 2

an equilibrium in which the species making up the reactants and products have different physical states

Question 3

Kc equation for heterogeneous equilibrium

Answer 3

concentration of solids and liquids are omitted as essentially constant

Question 4

mole fraction x(A) equation

Answer 4

number of moles of A / total number of moles in gas mixture

Question 5

partial pressure p(A) equation

Answer 5

mole fraction of A x total pressure P

Question 6

what is the sum of mole fractions?

Answer 6

1

Question 7

what is the sum of partial fractions?

Answer 7

total pressure

Question 8

Kp expression for A + B ⇌ C

Answer 8

Kp = p(C) / p(A) x p(B)

Question 9

what is the effect on K when temperature is increased?

Answer 9

for a exothermic reaction - K decreases, equilibrium shifts to the left, decreasing yield of products
for a endothermic reaction - K increases, equilibrium shifts to the right, increasing yield of products

Question 10

explain effect of increasing temperature on an exothermic reaction
A + B ⇌ C

Answer 10

K decreases
system no longer in equilibrium
ratio C / A x B greater than K
- the concentration/partial pressure of C must decrease
- the concentration/partial pressure of A and B must increase
- position of equilibrium shifts to the left
- new equilibrium reached where C / A x B = new K

Question 11

explain effect of increasing temperature on an exothermic reaction
A + B ⇌ C

Answer 11

K increases
system no longer in equilibrium
ratio C / A x B less than K
- the concentration/partial pressure of C must increase
- the concentration/partial pressure of A and B must decrease
- position of equilibrium shifts to the right
- new equilibrium reached where C / A x B = new K

Question 12

what is the effect on K when concentration is changed?

Answer 12

no effect on K

Question 13

what is the effect on K when pressure is changed?

Answer 13

no effect on K

Question 14

explain, in terms of K, the effect of changing concentration

A ⇌ 2B

Answer 14

• if [A] is increased
• ratio of [B]² / [A] is less than Kc
• system no longer in equilibrium
• [A] must decrease
• [B] must increase
• new equilibrium established where [B]² / [A] is restored to Kc

Question 15

explain, in terms of K, the effect of changing pressure

A ⇌ 2B

Answer 15

• if the total pressure is doubled
• ratio of p(B)² / p(A) is greater than Kp
• system no longer in equilibrium
• p(A) must increase
• p(B) must decrease
• new equilibrium established where [B]² / [A] is restored to Kp

Question 16

effect of increasing pressure when there are fewer moles of gaseous products

Answer 16

• ratio less than K
• products increase
• reactants decrease
• equilibrium shift right

Question 17

effect of increasing pressure when there are more moles of gaseous products

Answer 17

• ratio more than K
• products decrease
• reactants increase
• equilibrium shift left

Question 18

effect of increasing pressure when there are the same number of moles of gaseous reactants and products

Answer 18

• ratio = K
• no change
• no equilibrium shift

Question 19

how does a catalyst affect equilibrium constant?

Answer 19

K unaffected