Law of Mass Action:
According to this law, “the rate of reaction of a substance is proportional to the product of molar concentration of reactants at a constant temperature at any given time”. Molar concentration is called active mass. Active mass is the number of moles dissolved in one litre of solution.
eg. CH3COOH + C2H5OH ➝ CH3COOC2 H5 + H2O
According to law of mass action,
Rate of forward reaction a [CH3COOH] [C2H5OH]
= K1 [CH3COOH] [C2H5OH]
When K2 = rate constant for backward reaction At equilibrium,
Rate of backward reaction a [CH3COOC2H5] [H2O]
= K2 [CH3COOC2H5] [H2O]
Where K2 = rate constant for backward reaction At equilibrium,
Rate of forward reaction = Rate of backward reaction K2 [CH3COOH] [C2H6OH] – K2 [CH3COOC2H5] [H2O]
