L2.3: Determining the Direction of Reaction

• The Reaction Quotient Q

  ● Q gives the ratio of product concentrations to reactant concentrations at any point in a reaction.

  ● For a particular system and temperature, the same equilibrium state is attained regardless of starting concentrations.

  ○ The value of Q indicates how close the reaction is to equilibrium, and in which direction it must proceed to reach equilibrium.

  ○ The value of Q indicates the direction in which a reaction must proceed to reach equilibrium.
• Q < K

  ● The reactants must increase and the products decrease; reactants → products until equilibrium is reached.
• Q > K

  ● The reactants must decrease and the products increase; products → reactants until equilibrium is reached.
• Q = K

  ● The system is at equilibrium and no further net changes take place.