The Equilibrium Constant, Kc

• What does the equilibrium constant expression link ?

   the equilibrium constant, K, to the concentrations of reactants and products at equilibrium taking the stoichiometry of the equation into account
• what is the  equilibrium constant expression for aA + bB ⇌ cC + dD

  k = (C)^c(D)^d / (A)^a (B)^b where

  • [A] and [B] = equilibrium reactant concentrations (mol dm-3)
  • [C] and [D] = equilibrium product concentrations (mol dm-3)
• what are ignored in equilibrium constant equations

  solids
• does the Kc of a reaction change

  the Kc specific and only changes if the temperature of the reaction changes
• what does each figure within a square bracket represent

   the concentration in mol dm-3
• what should be used to determine the equilibrium concentration of the products using the molar ratio of reactants and products in the stoichiometric equation ?

  An initial, change and equilibrium table
• what does the magnitude of Kc indicate ?

  the relative concentrations of reactants and products in the mixture
• • If Kc is very large (Kc >>1) the equilibrium lies to the RHS so the reaction mixture contains mostly products
  • If Kc is very small (Kc << 1) the equilibrium lies to the LHS so the reaction mixture contains mostly reactants
  • If Kc is close to 1 the mixture contains a similar concentration of both reactant and products