Question

Dalton’s law of partial pressure cannot hold good for:
(A) ${\text{N}}{{\text{O}}_{\text{2}}}{\text{ + }}{{\text{O}}_{\text{2}}}$
(B) ${{\text{H}}_{\text{2}}}{\text{ + C}}{{\text{l}}_{\text{2}}}$
(C) ${\text{C}}{{\text{O}}_{\text{2}}}{\text{ + }}{{\text{O}}_{\text{2}}}$
(D) ${\text{N}}{{\text{H}}_{\text{3}}}{\text{ + He}}$

Answer 1

The gases which behave ideally follow Dalton’s law of partial pressure. Ideal gas condition is that where there is no collision between the molecules.

Complete step by step answer:
Ideal gas law is related to an individual sample of gas which means only one type of gas molecules is considered.
For the sample of gas which involves mixtures of different types of gas molecules made up of different substances. From Dalton’s law we will understand how gaseous mixtures behave. Suppose oxygen and nitrogen gases are taken in two different cylinders. The pressure remains constant of the individual gas sample until and unless there is no reaction taken place between the mixture of gaseous molecules. The pressure of the particular gas is known as partial pressure.
Thus to find the total pressure of the mixture we can add the partial pressure of the individual gas samples. This is stated in Dalton’s law.
Pressure is the force exerted as the particles strike the side of the container. So assuming that individual gases follow ideal gas behaviour, the total pressure will be:
${{\text{P}}_{\text{1}}}{\text{ + }}{{\text{P}}_{\text{2}}}{\text{ = }}{{\text{P}}_{\text{T}}}$
Here ${{\text{P}}_{\text{1}}}{\text{ = pressure of particle of one gas}}$
${\text{}}{{\text{P}}_{\text{2}}}{\text{ = pressure of particle of another gas}}$
${\text{}}{{\text{P}}_{\text{}}}{\text{ = total pressure}}$

Dalton’s law can also be expressed in terms of mole fraction.
${{\text{P}}_{\text{1}}}{\text{ = }}{{\text{x}}_{\text{1}}}{{\text{P}}_{\text{T}}}$
Mole fraction of a particular substance is the ratio of number of moles of that substance to the total number of moles of the mixture.
${{\text{x}}_{\text{1}}}{\text{ = mole fraction of gas 1 = }}\dfrac{{{\text{moles of gas1}}}}{{{\text{total moles of gas}}}}$
Dalton's law is applicable only when the component gases in the mixture do not react with each other.

So accordingly if we check the options,
Option (A) ${\text{N}}{{\text{O}}_{\text{2}}}{\text{ + }}{{\text{O}}_{\text{2}}}$ Nitrogen dioxide and oxygen gas both are not interactive with each other. Thus they follow Dalton’s law.

Option (B) ${{\text{H}}_{\text{2}}}{\text{ + C}}{{\text{l}}_{\text{2}}}$ Hydrogen and Chlorine gas are interactive with each other to form ${\text{HCl}}$l gas. Therefore they do not follow Dalton’s law.

Option (C) ${\text{C}}{{\text{O}}_{\text{2}}}{\text{ + }}{{\text{O}}_{\text{2}}}$ Carbon dioxide and oxygen gas both are not interactive with each other. Thus they follow Dalton’s law.

Option (D) ${\text{N}}{{\text{H}}_{\text{3}}}{\text{ + He}}$ Ammonia and helium gas are also not interactive with each other. Thus they follow Dalton’s law.
So, the correct answer is “Option C”.

Note: Ideal gas is the one whose properties are not affected by either the size of the particles nor the intermolecular interactions because both will be different for every gas. At constant temperature and volume, the pressure of the gas only depends on the number of moles of gas present whether it be a single chemical species or mixture of gases.