Question

Why dalton 's law of partial pressure can be applied only to a mixture of non reacting gases ?

Answer 1

Dalton's law of partial pressure states that in a mixture of non- reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the various gases present in the mixture.
The partial pressure is defined as the pressure of the gas would exert if it was alone in the container.

Answer 2

According to the Dalton's law of partial gases,

Total pressure of a mixture of non reactive gases = Sum of the partial pressures of those gases.

This theory is only applicable for the non-reactive gases because, the reaction between gases can produce solid or liquid materials which can change the whole pressure generating nature of that system.

That's why the non-reactive gases are must for the fulfillment of this theory.