the equilibrium constant- Kc

Question 1

what is the Kc equation?

Answer 1

concentration of products / concentration of reactants

Question 2

what does it mean if Kc is higher than 1?

Answer 2

there is a higher product concentration than reactant concentration so equilibrium lies to the right (products)

Question 3

what does it mean if Kc is lower than 1?

Answer 3

there is a higher reactant concentration than product concentration so equilibrium lies to the left (reactants)

Question 4

why do we need to be careful with heterogenous reactions in the Kc equation?

Answer 4

liquid/solid concentrations remain constant so are left out of the equation

Question 5

what do you do if a Kc calculation gives you the equilibrium concentrations?

Answer 5

substitute into the equation

Question 6

what do you do if a Kc calculation gives you the equilibrium moles and the volume?

Answer 6

moles / volume to work out concentrations
then substitute into equation

Question 7

what do you do if a Kc calculation gives you the initial moles and equilibrium moles of either a product or reactant?

Answer 7

use an ICE table

Question 8

describe how an ICE table works

Answer 8

1. use equilibrium moles and 0 initial moles to work out change
2. use this to work out the change of the other products/reactants (remember to divide / multiply based on big numbers)
3. use changes to work out all moles at equilibrium
4. moles / volume to work out concentrations
5. substitute into equation

Question 9

what factor affects the value of Kc?

Answer 9

temperature

Question 10

what happens to the value of Kc if temperature is increased in an EXOTHERMIC reaction? why?

Answer 10

decreases
- concentrations need to change to establish a lower equilibrium
- products decrease, reactants increase
- equilibrium shifts left (in endothermic direction)

Question 11

what happens to the value of Kc if temperature is increased in an ENDOTHERMIC reaction? why?

Answer 11

increases
- concentrations need to change to establish a higher equilibrium
- products increase, reactants decrease
- equilibrium shifts right (in endothermic direction)

Question 12

what happens to the POSITION OF EQUILIBRIUM if the concentration of reactants increases?

Answer 12

shifts right
- increases product conc
- decreases reactant conc

Question 13

what happens to the POSITION OF EQUILIBRIUM if the concentration of products increases?

Answer 13

shifts left
- decreases product conc
- increases reactant conc