In the thermal decomposition of potassium chlorate given as 2KClO3 → 2KCl+3O2, 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 temp and pressure

The law of mass action states that at equilibrium, the rate of a chemical reaction depends on the concentration (or pressure) of the reactants and products raised to their stoichiometric coefficients. It applies well to reactions that reach a dynamic equilibrium where forward and backward reactions occur at the same rate.

In the thermal decomposition of potassium chlorate:

$2KClO_3 \rightarrow 2KCl + 3O_2$

This is a decomposition reaction that is usually irreversible under normal conditions because the products (potassium chloride and oxygen gas) do not recombine easily to form potassium chlorate again. Since the backward reaction is negligible or absent, the system does not reach an equilibrium state where the law of mass action can be applied.

Therefore, the law of mass action cannot be applied to this reaction under normal conditions. It might be applicable if the reaction were reversible and equilibrium established, which generally requires specific conditions such as high pressure and temperature to favor recombination, but practically this is not the case here.

Imagine you have a big box of building blocks that can break apart into smaller pieces when heated. The law of mass action helps us understand how many blocks and pieces are there at the same time when the breaking happens. But sometimes, when the blocks break because of heat (like in this question), the law doesn't work well because the reaction is not balanced in the usual way. So, we need to know when this law can be used or not.

Given the reaction:

$2KClO_3 \rightarrow 2KCl + 3O_2$

• This is a thermal decomposition reaction.
• The law of mass action applies only when the reaction is reversible and equilibrium is established.
• Here, the backward reaction (recombination of KCl and O2 to form KClO3) is negligible.
• Therefore, no dynamic equilibrium is formed.

Hence, the law of mass action cannot be applied.

Answer: A) Cannot be applied