Topic 10 - Equilibrium I Flashcards
What is dynamic equilibrium ?
When the rate of the forward and backward reactions are the same in a closed system and there’s not net change in concentrations of reactants/products
What is the equilibrium constant (Kc) ?
gives an idea of how far left or right the equilibrium is
Explain homogeneous equilibria and Kc
homogeneous system = everything in the same state
working out the Kc involves the concentrations of all the reactants and products
How is Kc worked out (regardless of homogeneous or heterogeneous equilibria)
concentration of products to the power of the number of moles divided by the concentration of reactants to the power of the number of moles
Explain heterogeneous equilibria and Kc
heterogeneous system = not everything in the same state
solids and pure liquids not included in Kc - as their concentrations remain constant
Why are catalysts not included in Kc
they don’t affect the equilibrium concentrations of products or reactants - just speeds up rate at which dynamic equilibrium reached
What is Le Chatelier’s Principle ?
If there is a change in concentration, principle or temperature, the equilibrium will move to help counteract the change
What affect does change in concentration have on equilibrium ?
- increase of reactant = get rid of extra by making more product = shift right
- increases product = get rid of extra by making more reactants = shift left
What affect does change in pressure have on equilibrium ?
- increase = shift to side of fewer molecules to reduce pressure
- decrease = shift to side of more molecules to increase pressure
What affect does change in temperature have on equilibrium ?
- increase = adding heat so favours endothermic reaction to absorb it
- decrease = removing heat so favours exothermic reaction to replace it
What is the Haber process ? include equation
exothermic reaction of the production of ammonia (fertiliser)
N₂ (g) + 3H₂ (g) ⇌ 2NH₃ (g)
What are the conditions of the Haber process
450℃
200 atm
iron catalyst
Explain the compromise for temperature and pressure
temperature:
- lower temp favours exothermic reaction
- more NH₃ produced
- high enough that reaction is not too slow
pressure :
- higher pressure shifts equilibrium to the right (fewer molecules)
- more NH₃ produced
- compromise of yield and cost as expensive to build container for very high pressures
What is the contact process? include equations
the production of sulfuric acid
S (s) + O₂ (g) →SO₂ (g)
2SO₂ (g) + O₂ (g) ⇌ 2SO₃ (g)
SO₃ (g) + H₂SO₄ (l)→H₂S₂O₇ (l)
H₂S₂O₇ (l) + H₂O (l)→2H₂SO₄ (l)
Why is SO₃ not immediately added to H₂O ?
uncontrollable reaction = dangerous
