Question

Air contains 79% $N_2$ and 21% $O_2$ by volume. If the pressure is $750$ of $Hg$, the partial pressure of $O_2$ is:

• A. $157.5$ of $Hg$
• B. $175.5$ of $Hg$
• C. $315.0$ of $Hg$
• D. $257.5$ of $Hg$

Answer 1

Answer: (A)

$157.5$ of $Hg$

Solution:- (A) $157.5\text{mm of Hg}$

Given:-

Total pressure $\left(P\right)=750\text{mm of Hg}$

Percentage of $O_2$ in air $=21\%$

Therefore,

$P_{O_2}=\frac{\%\text{of}{O}_2\text{in the air}}{100}\times P$

$\Rightarrow P_{O_2}=\frac{21}{100}\times 750=157.5\text{mm of Hg}$

Hence the partial pressure of $O_2$ is $157.5\text{mm of Hg}$.