Equilibrium Constant: Characteristics

Equilibrium in a system having two (or) more phases is known as heterogeneous equilibrium. Heterogeneous equilibria often involve pure solids (or) liquids.

Consider the thermal decomposition of calcium carbonate in a closed vessel, the equilibrium constant for this reaction can be written as

CaCO3(s) ⇌  CaO (S)  + CO 2

Kc = [CaO][ CO 2 ] [ CaCO 3 ]

Since calcium carbonate and calcium oxide are solids, their concentrations remain constant, and hence, their concentration terms in the expression for equilibrium constant can be ignored.

K'c = [CO2] or Kp = pCO2

It shows that at a particular temperature, irrespective of the masses of the two solids Calcium oxide and Calcium carbonate, there is a constant concentration or pressure of Carbon dioxide in equilibrium with calcium oxide and calcium carbonate.

Characteristics of equilibrium:

  • The value of equilibrium constant is independent of the initial concentrations of the reactants and products.
  • The equilibrium constant for a particular reaction at a particular temperature is always constant and changes only with a change in temperature.
  • The equilibrium constants of a forward reaction and its backward reaction are reciprocals of each other.
  • If a chemical equation is multiplied by a certain factor, then its equilibrium constant must be raised to a power equal to that factor in order to obtain the equilibrium constant for the new reaction.

Summary

Equilibrium in a system having two (or) more phases is known as heterogeneous equilibrium. Heterogeneous equilibria often involve pure solids (or) liquids.

Consider the thermal decomposition of calcium carbonate in a closed vessel, the equilibrium constant for this reaction can be written as

CaCO3(s) ⇌  CaO (S)  + CO 2

Kc = [CaO][ CO 2 ] [ CaCO 3 ]

Since calcium carbonate and calcium oxide are solids, their concentrations remain constant, and hence, their concentration terms in the expression for equilibrium constant can be ignored.

K'c = [CO2] or Kp = pCO2

It shows that at a particular temperature, irrespective of the masses of the two solids Calcium oxide and Calcium carbonate, there is a constant concentration or pressure of Carbon dioxide in equilibrium with calcium oxide and calcium carbonate.

Characteristics of equilibrium:

  • The value of equilibrium constant is independent of the initial concentrations of the reactants and products.
  • The equilibrium constant for a particular reaction at a particular temperature is always constant and changes only with a change in temperature.
  • The equilibrium constants of a forward reaction and its backward reaction are reciprocals of each other.
  • If a chemical equation is multiplied by a certain factor, then its equilibrium constant must be raised to a power equal to that factor in order to obtain the equilibrium constant for the new reaction.

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