m3 - equilibrium

Question 1

examples of reversible processes

Answer 1

changing state eg freezing
the Haber process - producing ammonia (iron catalyst)
SO2 + O2

Question 2

how/where is dynamic equilibrium reached (3 things)

Answer 2

closed system - nothing can get in or out
rate of forward reaction = rate of reverse reaction
when the conc of reactants = products

Question 3

what 3 things change position of equilibrium

Answer 3

concentration
pressure (gases)
temperature

Question 4

effect of concentration on equilibrium

Answer 4

increase reactant conc, equilibrium favours forward reaction (to get rid of these new reactants), moves to the right
increase product conc, equilibrium favours backward reaction, moves to the left

Question 5

effect of temp on equilibrium 

Answer 5

increasing temp (means more energy so want to take it away) - favoured by endothermic reactions
decreasing temp (taking energy away, want to put it back) - favoured by exothermic reactions

Question 6

effect of pressure on equilibrium (only in gas reactions)

Answer 6

increasing pressure favours reaction with a decrease in total no of moles (shifts to side with less moles)
decreasing pressure favours reactions with an increase in total no of moles

Question 7

equilibrium constant reaction (Kc)

Answer 7

[C^moles] x [D^moles]
—————————————
[A^moles] x [B^moles]

Question 8

Haber process pressure and temperature

Answer 8

200atm
450°C

Question 9

how does catalyst affect position of equilibrium

Answer 9

it doesn’t, it increases rate of forward and backward reactions by the same amount

Question 10

compromise between rate of reaction and yield

Answer 10

want a relatively good rate and yield
eg if yield was only taken into account, rate may be too low that the reaction is unuseful

also safety, too high pressure may not be safe
also expensive

Question 11

what factors effect Kc and Kp (equilibrium constant)

Answer 11

temperature only

(conc, pressure and catalysts only affect rate not position)

Question 12

how to work out mole fraction

Answer 12

molecules of X
———————
total molecules

Question 13

partial pressure equation

Answer 13

partial pressure of X = mole fraction x total pressure

(mole fraction = molecules of X / total molecules)

Question 14

how to work out Kc

Answer 14

conc products
———————
conc reactants

2 moles of something means you’d square it

Question 15

Kc and Kp expressions in homogenous vs heterogeneous reactions

Answer 15

normal in homo

in herero: concentration of any solids aren’t counted in the equation

Question 16

what is Kp and how to calculate it

Answer 16

gaseous equilibrium constant

partial pressure of products
——————————————
partial pressure of reactants

Question 17

units will change but normal units for Kp

Answer 17

kPa-1