Year 12- Equilibria (Physical Chemistry) Flashcards
What is dynamic equilibrium?
When both forward and backwards reactions occur simultaneously at equal rates. The concentrations of both reactants and products stay constant.
What does Le Chatelier’s principle state?
If an external condition is changed, the equilibrium will shift to oppose it and reverse it.
Effect of increasing temperature on the equilibrium
The equilibrium will shift to the endothermic direction to reduce temperature by absorbing heat.
Effect of decreasing temperature on the equilibrium
The equilibrium will move in the exothermic direction to increase temperature by releasing heat.
Effect of increasing pressure on equilibrium
Shifts to side with fewer moles of gas to reduce pressure
Effect of decreasing pressure on equilibrium
Shifts to side with more moles of gas to increase pressure
Effect of high pressure in industry
May give a higher yield of product and produce faster rate. However, this is expensive to produce (high electrical costs for pumping gases to make high pressure) and equipment is expensive to maintain it.
Effect of high temperature in industry
May produce high yield of product but a slow rate. This is why a compromise temperature is used.
Effect of increased concentration of equilibrium
Shifts in opposite direction
Effect of catalyst on equilibrium
No effect on equilibrium position as it speeds up forward and backwards reactions at the same rate but speeds up the rate at which equilibrium is achieved.
Conditions of haber process
T= 450 *C P= 200-1000 atm Catalyst= iron
Importance of equilibrium to haber process
- Low temp gives good yield but slow rate so comp. temp used
- High pressure gives good yield and high rate- this leads to too high energy costs for pumps
Contact process stages
1= S (s) + O2
(g) –> SO2
(g)
2= SO2 (g) +½O2 (g) ⇌ SO3 (g)
Equation for kc
Kc= [C][D]/[A][B]]
What affects the value Kc?
Temperature only
