A mixture of hydrogen and oxygen at `1` bar pressure contains `20%` of hydrogen by weight. Calculate the partial pressure of hydrogen.

Answer

0.8 bar

Explanation

Let the weight of dihydrogen be 20 g and the weight of dioxygen be 80 g.
Then, the number of moles of dihydrogen, `n_(H_2)=(20)/(2)=10` moles and the number of moles
of dioxygen, `n_(O_2)=(80)/(32)=2.5` moles
Given,
Total pressure os the mixture, `p_("total")` = 1 bar
Then partial pressure of dihydrogen,
`P_(H_2)=(n_(H_2))/(n_(H_2)+n_(O_2))xxP_("total")`
`=(10)/(10+2.5)xx1`
= 0.8 bar
Hence, the partial pressure of dihydrogen is 0.8 bar.