Question

A flask contains three times as many moles of $H_2$ gas as it does $O_2$ gas. If hydrogen and oxygen are the only gases present, what is the total pressure in the flask if the partial pressure due to oxygen is $P$?

• A. $4P$
• B. $3P$
• C. $\frac{4}{3}P$
• D. $\frac{3}{4}P$

Answer 1

The correct option is A $4P$

According to Dalton's law of partial pressure,

$p_{O_2}={\chi }_{O_2}{P}_{total}$

${\chi }_{O_2}=\frac{n_{O_2}}{n_{O_2}+3n_{O_2}}=0.25$

Hence,

$P=0.25\times P_{total}$

$P_{total}=4P$