CHEM EQUILL

Question 1

What is a reversible reaction

Answer 1

It refers to a reaction that can proceed in both the forward and backwards direction, is never complete and only attains dynamic equillibrium

Question 2

What is a dynamic equillibrium

Answer 2

It refers to a reversible reaction that experiences no changes in concentrations of products or reactants

Question 3

What are the characteristics of a dynamic equillibrium

Answer 3

(i) no net change in concentrations of products or reactants

(ii) can only be attained in a closed system

Question 4

What types of dynamic equillibrium are there

Answer 4

(i) homogeneous

(ii) heterogeneous

Question 5

What is a homogeneous equillibrium

Answer 5

It is an equillibrium that is reached when the reactants of products are in the same phase

Question 6

What is a heterogeneous equillibrium

Answer 6

It is an equillibrium reached when the products and reactants are in different phases

Question 7

What properties of the equillibrium constant are there

Answer 7

(i) it is mathematically determined by the equillibrium concentrations alone
(ii) it is dependant on the rate constants of forward and backward reactions - dependant on temperature
(iii) does not take into account concentrations of products or reactants that remain essentially the same in initial and equillibrium state

Question 8

What exceptions of concentrations does it not take into account

Answer 8

(i) immiscible liquids
(ii) solids
(iii) water

Question 9

What is the difference between Kp and Kc

Answer 9

Kp is in terms of equillibrium partial pressure while Kc is in terms of equillibrium concentrations

Question 10

How do you find equillibrium constant if not all concentrations are given

Answer 10

Initial
Change
Equillibrum
table can be used as changes of concentrations are mathematically determined by stoichometric ratio of reaction

Question 11

What is the significance of the value of equillibrium constant

Answer 11

(i) position of equillibrium (extent of reaction
(ii) value of change in Gibbs’ Free Energy
(iii) the equillibrium constant is independant of changes in initial concentrations or catalyst

Question 12

What does it mean if equillibrium constant is large (change in G)wise

Answer 12

If equillibrium constant is large, it suggests that the forwards reaction is more spontaneous than the backwards reaction by a large extent. Hence the change in G is negative.

Question 13

What does it mean if equillibrium constant is low (change in G)wise

Answer 13

It suggests that the forward reaction is less spontaneous than the backwards reaction. So the change in G is positive

Question 14

What does it mean if the equillibrium constant is large (position of equillibrium)wise

Answer 14

It suggests that for dynamic equillibrium to be reached, a greater concentration of product is needed than reactants. So, the position of equillibrium lies more to the right

Question 15

What does it mean if the equillibrium constant is small (position of equillibrium)wise

Answer 15

It suggests that for dynamic equillubrium to be attained, a larger concentration of reactants is needed. So the position of equillibrium lies more to the left

Question 16

What does it mean if the equillibrium constant is directly proportional to the temperature

Answer 16

It suggests that the the enthalpy change is endothermic

Question 17

What does it mean if the equillibrium constant is inversely proportional to temperature

Answer 17

It suggests that the forward reaction is exothermic

Question 18

What is Le Chatelier’s principle

Answer 18

It states that when a system in equillibrium is disturbed, it will change its position of equillibrium to counteract the change imposed to re-establish equillibrium

Question 19

What changes will cause the position of equillibrium to change

Answer 19

(i) change in concentration of reactants or products
(ii) change in partial pressure of reactants or products
(iii) change in total pressure
(iv) change in temperature

Question 20

How does an increase in concentration of products induce a change in position of equillibrium

Answer 20

An increase in products will result in the backwards reaction being favoured to counteract the increase in concentration products. Thus position of equillibrium lies more to the left

Question 21

How does an increase in total pressure change position of equillibrium

Answer 21

Dependant on stoichometric ratio - the system will favour the reaction that produces fewer gaseous molecules. Position of equillibrium shifts leftwards if backward reaction, opposite if forward

Question 22

Do changes in pressure or concentration affect equillibrium constant

Answer 22

No.

Question 23

How does an increase in temperature affect the system of a reversible reaction with a exothermic forward reaction

Answer 23

The system will favour the backward reaction to counteract the increase in temperature as it is endothermic. This shifts position of equillibrium leftwards while equillibrium constant decreases

Question 24

Does increasing total pressure by inserting inert gas change position of equillibrium

Answer 24

No. Partial pressures of product and reactants remain the same, thus total pressure of system remains undisturbed

(System refering solely to product and reactants)

Question 25

Will adding a catalyst change position of equillibrium

Answer 25

No. Both rate of reactions inconsiderate of directions increases by the same extent. However, progession towards dynamic equillibrium is faster