Question

What is chemical equilibrium? Describe the factors that can affect chemical equilibrium, including the presence of catalysts. Explain Le Châtelier’s principle and explain how chemists might use it to increase the amount of products produced in a reaction. (Equilibrium)

Answer 1

••Chemical equilibrium refers to the state wherein both the reactants and the products present in the concentration have no tendency to change with the period of time during a chemical reaction. A chemical reaction achieves chemical equilibrium when the rate of forward reaction and that of the reverse reaction is same. Also, since the rates are equal and there is no net change in the concentrations of the reactants and the products – the state is referred to as a dynamic equilibrium and the rate constant is known as equilibrium constant.

••Factors affecting chemical equilibrium ;

According to the Le Chatelier’s Principle, states that if a system under equilibrium is subjected to a change in pressure, temperature or concentration, in this case, the equilibrium shifts further reducing as well as to counteract the effect of the change. The factors that affect equilibria are:

Effect of Pressure Change

There is no effect of pressure if the number of moles of gaseous reactant and products is equalised. However, it is different for the total number of moles of gaseous reactants and a total number of moles of gaseous products. On increasing the pressure, the total number of moles per unit volume also increases leading to shifting in the equilibrium direction wherein the number of moles per unit volume will be less.

If the total number of moles of products are more than the total number of moles of reactants, in this case, the low pressure will also favour forward reaction. If the number of moles of reactants is more than that of products, high pressure would be favourable to forward reaction.

Effect of Change of Concentration

The equilibrium changes when the concentration of any reactants or products in the reaction changes. It further leads to minimising its effect.

Effect of Inert Gas Addition

After the addition of an inert gas and with the volume kept constant, there is no effect on the equilibrium. This is because, at constant volume, the addition of an inert gas does not change partial pressure or molar concentration.