Chemical equilibria, Le Chatelier’s principle and Kc Flashcards
define dynamic
both forward and backward reactions
are occurring simultaneously
describe the two features of dynamic equilibrium
- Forward and backward reactions are occurring at equal rates.
- The concentrations of reactants and products stay
constant
what does Le Chatelier’s principle state
if an external condition is changed the equilibrium will shift to oppose the change
Effect of temperature on equilibrium
If temperature is increased the equilibrium will shift to oppose this and move in the endothermic direction to try to reduce the temperature
If temperature is decreased the equilibrium will shift to oppose this and move in the exothermic direction to try to increase the temperature.
why is a compromise temperature sometimes used
Low temperatures may give a higher yield of product but will also result in slow rates of reaction.
Effect of pressure on equilibrium
Increasing pressure will cause the equilibrium to shift towards the side with fewer moles of gas to oppose the change and thereby reduce the pressure.
Decreasing pressure will cause the equilibrium to shift towards the side with more moles of gas to oppose the change and thereby increase the pressure.
Effect of Concentration on Equilibrium
Increasing the concentration OH- ions causes the equilibrium to shift to oppose this and move in the forward direction to remove and decrease the concentration of OH- ions.
Effect of Catalysts on Equilibrium
A catalyst has no effect on the position of equilibrium, but it will speed up the rate at which the equilibrium is achieved.
why does the catalyst have no effect on equilibrium
It does not effect the position of equilibrium because it speeds up the rates of the forward and backward reactions by the same amount.
Importance of equilibrium to industrial processes: Haber process equation
N2 + 3H2 ⇌ 2NH3 H = = -ve exo
production of methanol from CO
CO (g) + 2H2(g) ⇌ CH3OH (g)H = -ve exo
Hydration of ethene to produce ethanol
CH2=CH2 (g) + H2O (g) ⇌ CH3CH2OH(l) H=-ve
what does high pressure lead to
leads to too high energy costs for pumps to produce the pressure and too high
equipment costs
what does low temperature lead to
good yield but slow rate:
compromise temp used
