Equilibria

Equilibria

Many reactions are reversible
1. Eg. alcohol + carboxylic acid <--> ester + water
For any reaction that reaches an equilibrium
1. aA + bB + cC <--> xX + yY + zZ
2. Kc = ([X]^x [Y]^y [Z]^z) / ([A]^a [B]^b [C]^c)
  1. Kc = equilibrium constant
    1. This varies for different reactions
    2. The units change depending on the reactants
  2. [X] = concentration of X
    1. units = mol dm^-3
  3. x = the number of moles of substance X
3. Kc = [products] / [reactants]
Dynamic Equilibrium = the rate of the forwards reaction is equal to the reverse reaction
When doing calculations using the equilibrium constant expressions, make sure you divide everything by the volume of the system
1. The volumes may cancel
Endothermic reactions (positive∆H)
1. Decrease of temperature
  1. causes Kc to decrease
  2. causes the products to decrease
  3. causes the reactants to increase
  4. the equilibrium moves left
2. Increase of temperature
  1. causes Kc to increase
  2. causes the products to increase
  3. causes the reactants to decrease
  4. the equilibrium moves right
Exothermic reactions (negative ∆H)
1. Increase of temperature
  1. causes Kc to decrease
  2. causes the products to decrease
  3. causes the reactants to increase
  4. the equilibrium moves left
2. Decrease of temperature
  1. causes Kc to increase
  2. causes the products to increase
  3. causes the reactants to decrease
  4. the equilibrium moves right
Catalysts
1. They have no effect on the position of the equilibrium

Resource summary

	Created by Amy Holden about 9 years ago