3.2.3 chemical eqilibrium

Question 1

when does dynamic equilibrium exist in a closed system

Answer 1

-forward reaction has same rate as reverse reaction
-concentration of products and reactants remains constant overtime

Question 2

what is the value of Kc

Answer 2

concentration of products
concentration of reactants

Question 3

if the concentration of products is greater than the concentration of reactants what does this mean

Answer 3

kc is greater than 1

Question 4

if the concentration of reactant is greater than the concentration of product what does this mean

Answer 4

kc is less than 1

Question 5

what do we use molar values as in Kc

Answer 5

indices

Question 6

what is homogenous equilibria

Answer 6

when the reactants and products are in the same state
eg-(s) or (aq)

Question 7

what is heterogenous equilibria

Answer 7

some of the reactants and products are in different states

Question 8

in heterogenous equilibria if some of the reactants or products are solid or liquid what do we do with these

Answer 8

we don’t use them in out Kc equation

Question 9

when calculating out units for Kc what should we do if we get
1/moldm-3

Answer 9

flip the indices

Question 10

what is the effect of the increasing the concentration of reactants on the position of equilibrium
what will happen to Kc

Answer 10

equilibrium will shift to the right (towards the products)
Kc remains constant

Question 11

what is the effect of the increasing the pressure on the position of equilibrium
what will happen to Kc

Answer 11

equilibrium will move to the side with the fewest moles
-Kc remains constant

Question 12

if we increase temperature and forward reaction is exothermic what is the effect on the position of equilibrium
what happens to Kc

Answer 12

equilibrium will move in the endothermic direction and (amount of product will decrease)
so Kc will decrease

Question 13

if we decrease temperature and forward reaction is exothermic what is the effect on the position of equilibrium
what happens to Kc

Answer 13

equilibrium will move in the exothermic direction (amount of product will increase
so Kc will increase

Question 14

what is the impact of using a catalyst on the position of equilibrium

Answer 14

no impact
it increases the rate of the forward and backword reaction by the same amount

Question 15

what is the compromise for high temperature

Answer 15

gives a high rate but a low yield for exothermic reactions
requires a lot of energy burning fossil fuels which releases co2

Question 16

what is the compromise for high pressure

Answer 16

increases rate but will decrease yield if there are more moles on the product side
-can be dangerous
-expensive

Question 17

what is the compromise for a catalyst

Answer 17

can be toxic
but allows reaction to be done at a lower temperature

Question 18

what is le chataliers principle

Answer 18

if the conditions on a system in equilibrium are changed (1)
the equilibrium moves to try to minimise the effects of the change

Question 19

if you are moving equilibrium in the exothermic direction what do you do

Answer 19

decrease temperature

Question 20

if you are moving equilibrium in the endothermic direction what do you do

Answer 20

increase temperature