EQUILIBRIA Flashcards
what are the 3 features of a dynamic equilibrium?
- the concentration of reactants and products remain the same
- forward reactions and background reactions occuring at equal rates
- reaction is in a closed system (nothing can get in or out)
explain the Le Chatelier’s principle:
If the conditions (e.g. temperature ,concentration,pressure)of a reaction are changed the equilibrium will shift to oppose the change.
effect of decreasing temperature on equilibrium:
PCl3(g)+Cl2(g)⇌PCl5(g) △H=-129.7 Kj/mol-1
- equilibrium shift to increase temperature
- equilibrium arrow shifts towards RHS as its exothermic
- Yield increases (more PCl5) is mad
what is the effect of increasing temperature on equilibrium?
PCl3(g)+Cl2(g)⇌PCl5(g) △H=-129.7 Kj/mol-1
- equilibrium will shift to decrease temperature
- equilibrium arrow will shift to LHS as its endothermic
- Yield decreases
What is the effect of increasing pressure on equilibrium?
PCl3(g)+Cl2(g)⇌PCl5(g) △H=-129.7 Kj/mol-1
There are more moles of the left &equilibrium arrow shifts to decrease pressure
- Equilibrium arrow shift to RHS to oppose the increase in pressure
- Yield increases(more PCl5 is made)
What effect does adding a catalyst have on equilibrium?
catalyst has no effect on position of equilibrium ,but it ensures equilibrium is reached faster
-speeds up the rate of forward&backward reaction equally.
What are the optimum conditions for the haber process?
N2 + 3H2 ⇌ 2NH3 △H = -92 kj mol-1
increasing pressure-it will cause the position of the equilibrium to shift to the right, favouring the forwards reaction as there are fewer moles on the right (two moles) than on the left (four moles). Therefore, more ammonia is produced and the pressure will be reduced, opposing the change
-Low temperature — the forward reaction is exothermic, so decreasing the temperature will cause the position of equilibrium to shift to the right, favouring the forwards reaction. Therefore, more ammonia is produced and the temperature increases, opposing the change
Why aren’t the optimum conditions for the haber process nor favorable/?
-Low temp gives good yield but slow rate:
compromise temp used
-High pressure gives good yield and high rate: too
high a pressure would lead to too high energy costs
for pumps to produce the pressure
what are the industrial,compromised conditions used for the Haber process today
temperature-400°c
pressure=200atm
catalyst=iron
Formula for equilibrium constant kc?
kc=[product]/[reactant]
How does increasing temperature effect Kc /
It decreases kc
How does decreasing temperature effect kc?
it increases kc
what effect does a catalyst have on kc?
no effect
what effect does concentration and pressure have on kc?
no effect
