Question

At room temperature Dalton’s law of partial pressure is not applicable to:
(A) ${H_2}$ and ${N_2}$ mixture
(B) ${H_2}$ and $C{l_2}$ mixture
(C) ${H_2}$ and $C{O_2}$ mixture
(D) None of these

Answer 1

Dalton’s law states that, in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases. This law was observed by John Dalton in $1801$ and was published in $1802$. It is related to the ideal gas law.

Complete step by step answer:
Dalton's law states that the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures exerted by each individual gas in the mixture and this law is applicable to non-reacting gas mixtures.
For example, the total pressure exerted by a mixture of two gases A and B is equal to the sum of the individual partial pressures exerted by gas A and gas B.
Now, in terms of mole fraction, the mole fraction of a specific gas in a mixture of gases is equal to the ratio of the partial pressure of that gas to the total pressure exerted by the gaseous mixture.
We can use this mole fraction to calculate the total number of moles of a constituent gas when the total number of moles in the mixture is known.
Further, we can also calculate the volume occupied by a specific gas with this mole fraction by the equation given below:
${X_i} = \dfrac{{{P_i}}}{{{P_{total}}}} = \dfrac{{{V_i}}}{{{V_{total}}}} = \dfrac{{{n_i}}}{{{n_{total}}}}$
Where, $'{X_i}'$ is the mole fraction of gas
‘i’ is the mixture of n gases
N denotes the number of moles
P denotes pressure and V denotes volume.
Therefore, among the given options, ${H_2}$ and $C{l_2}$ may react at room temperature to form HCl and we know that Dalton’s law is only applicable to non-reacting gases.

Hence, option B is correct.

Note: Partial pressure refers to the force exerted by a gas. In a mixture, the partial pressure of each gas is proportional to its fraction of the mole. The pressure exerted by each gas in a as mixture is independent of the pressure exerted by all the other gases present.