Question

In the thermal decomposition of potassium chlorate given as $2KCl{O_3}\xrightarrow{{}}2KCl + 3{O_2}$ , the law of mass action
a.) Cannot be applied
b.) Can be applied
c.) Can be applied at low temperature
d.) Can be applied at high temperature and pressure

Answer 1

Hint: The law of mass action states that the rate of a chemical reaction is directly proportional to the active masses of the reacting substances. This law is only applicable to reversible reaction and since $2KCl{O_3}\xrightarrow{{}}2KCl + 3{O_2}$ is an irreversible reaction, the law of mass action does not apply for this reaction.

Complete step by step answer:
Before moving on to the solution, it would be beneficial to discuss the law of mass action first.
According to the law of mass action, the rate of a chemical reaction is directly proportional to the product of the concentrations or activities of the reactants involved in the reactions.
Or The law of mass action states that the rate of a chemical reaction is directly proportional to the active masses (the mass of the substance that is reacting) of the reacting substances.
This law applies only to solutions in a dynamic equilibrium, meaning that it is only applicable to reversible reactions.
Now let’s discuss the thermal decomposition of potassium chlorate
$2KCl{O_3}\xrightarrow{{}}2KCl + 3{O_2}$
This reaction is irreversible.
Now, as we discussed earlier the law of mass action is only applicable to reversible reactions, so the reaction in which thermal decomposition of potassium chlorate takes place is not governed by the law of mass action.
So, the correct answer is “Option A”.

Note: In the solution above we discussed the law of mass action. The law of mass action is used to explain and predict the behavior of solutions that are in a dynamic equilibrium. This law also tells us that the ratio between the concentration of reactants and products is constant for a reaction in equilibrium.