Question

The density of a mixture of ${\mathrm{O}}_2\mathrm{and}{\mathrm{N}}_2\mathrm{is}1.33\mathrm{g}/\mathrm{L}$. Calculate the partial pressure of O₂.

Answer 1

Step 1: Formula for density :

We know : Density = volume / mass

Let 1 mol of gas be present. So, $22.4L$ will be the volume of the mixture

Assuming % of the oxygen present in mixture = x

% of nitrogen present in mixture = $1–x$

We know, the Molar Mass of oxygen and nitrogen are$32\mathrm{and}28\mathrm{g}/\mathrm{mol}$respectively

Step 2: Calculating the Molar Mass of the Mixture:

Calculating the Molar Mass of the Mixture as

$1.3\times 22.4=29.12\mathrm{g}/\mathrm{mol}$

Step 3: Calculating Partial pressure :

Thus, on applying atomic weights of both gases we get:

$$\begin{gathered} 32\left(x\right)+28(1–x)=29.12 \\ x=0.28 \end{gathered}$$

Hence Partial pressure of${\mathrm{O}}_2$ is $0.28\mathrm{atm}$.