Reversible Reactions

Reversible Reactions

Definition

  • A reversible reaction is a chemical reaction where the reactants react together to form products, but the products can also react together to reform the original reactants.

  • They are generally represented by a two-headed arrow in a chemical equation, signifying that the reaction can proceed in both directions.

Equilibrium in Reversible Reactions

  • Chemical equilibrium is a dynamic state in a reversible reaction where the forward and backward reaction rates are equal, meaning the concentrations of reactants and products remain constant over time.

  • At equilibrium, the reaction hasn’t stopped. Rather, the rates of the forward and backward reactions are the same, so there’s no net change in the amount of reactants and products.

Effect of Temperature in Reversible Reactions

  • In a reversible reaction, increasing the temperature tends to shift the equilibrium position in the direction of the endothermic reaction (the reaction that absorbs heat).

  • Lowering the temperature tends to shift the equilibrium position in the direction of the exothermic reaction (the reaction that releases heat).

Effect of Pressure in Reversible Reactions

  • For reactions that involve gases, changing the pressure can shift the equilibrium position.

  • If the pressure is increased, the equilibrium position will shift to the side with the fewer number of gas molecules. If the pressure is decreased, the equilibrium position will move to the side with more gas molecules.

Effect of Concentration in Reversible Reactions

  • If the concentration of one of the reactants is increased, the equilibrium position will shift in the direction that uses up the added substance.

  • If the concentration of one of the products is decreased, the equilibrium will shift in the direction that produces more of that substance.

Le Chatelier’s Principle

  • Le Chatelier’s Principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium evolves to counteract the change.

  • This principle helps to predict the effect of change in condition (temperature, pressure, concentration) on the position of equilibrium in a reversible reaction.