Suppose than 1 . 28 g of neon gas and 2 . 49 g of argon gas. Are confined in a 9 . 87 − L container at 27  ° C . What would be the pressure in the container?

Interpretation:

The partial pressure of each gas and total pressure of the container should be calculated.

Concept Introduction:

Dalton’s law of partial pressure: In a container for mixture of gases, the total pressure is equal to the sum of partial pressures of all the gases present in the container. The partial pressure is the pressure exerted by a gas if it is the only gas present in the container.

Let a mixture of three gases with partial pressures P1, P2 and P3, the total pressure of the gas will be sum of these partial pressures as follows:

PT=P1+P2+P3

This is the Dalton’s law of partial pressure.

The behaviour of gases is assumed to be ideal thus, partial pressure of gases can be calculated from an ideal gas equation as follows:

PV=nRT

Here, P is pressure, V is volume, n is number of moles, R is Universal gas constant and T is temperature of the gas.

The pressure exerted by an ideal gas depends on the number of gas particles, this does not depend on the nature of particles of gas. The two important things concluded from it will be:

1. The volume of gases is important.
2. The forces in between the particles of gas is not important.

Given Information:

The mass of neon gas is 1.28 g and that of argon gas is 2.49 g. The volume of container is 9.87 L and temperature is 27 ∘C.

Calculation:

Number of moles of Ne and Ar gas can be calculated as follows:

n=mM

Molar mass of Ne is 20.18 g/mol and that of Ar is 39.948 g/mol thus, number of moles will be:

nNe=1.28 g20.18 g/mol=0.0634 mol

Similarly, number of moles of Ar can be calculated as follows:

nAr=2.49 g39.948 g/mol=0.0623 mol

Now, partial pressure of neon and argon can be calculated using the ideal gas equation:

P=nRTV

First convert the temperature from ∘C to K as follows:

0 ∘C=273.15 K

Thus,

27 ∘C=(27+273.15) K=300.15 K

For Neon, partial pressure will be:

PNe=(0