Q and K are used to describe the state of equilibrium in a chemical reaction

K = Equilibrium constant

K represents the equilibrium constant, which is calculated using the equilibrium concentrations (or partial pressures) of the reactants and products. 

Q = Reaction Quotient 

Q represents the reaction quotient, which is calculated using the concentrations (or partial pressures) of the reactants and products at any given moment during the reaction. It helps us determine whether the reaction is at equilibrium or not. 

K vs Q: Comparing and Contrasting

• Both K and Q: Use the same formula but differ in the context of their application.

• Interpreting Q relative to K:

  • Q < K: The reaction will proceed in the forward direction to reach equilibrium.

  • Q > K: The reaction will proceed in the reverse direction to reach equilibrium.

  • Q = K: The system is at equilibrium.