Kc

Question 1

what is meant by Kc?

Answer 1

the equilibrium constant

Question 2

what is the Kc equation?

Answer 2

concentration of products / concentration of reactants

Question 3

what does it mean if Kc is higher than 1?

Answer 3

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

Question 4

what does it mean if Kc is lower than 1?

Answer 4

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

Question 5

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

Answer 5

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

Question 6

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

Answer 6

substitute into the equation

Question 7

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

Answer 7

moles / volume to work out concentrations
then substitute into equation

Question 8

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

Answer 8

use an ICE table

Question 9

describe how an ICE table works

Answer 9

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 10

what factor affects the value of Kc?

Answer 10

temperature

Question 11

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

Answer 11

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

Question 12

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

Answer 12

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

Question 13

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

Answer 13

shifts right
- increases product conc
- decreases reactant conc

Question 14

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

Answer 14

shifts left
- decreases product conc
- increases reactant conc