Question

A mixture of dihydrogen and dioxygen at one bar pressure contains 20% by weight of dihydrogen. Calculate the partial pressure of dihydrogen.

Answer 1

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` and the number of moles of dioxygen, `"n"_("O"_2) = 80/32 = 2.5` moles

Given,

Total pressure of the mixture, `"p"_"total"` = 1 bar

Then, partial pressure of dihydrogen,

`"p"_("H"_2) = "n"_("H"_2)/("n"_("H"_2) + 'n"_("O"_2)) xx "P"_"total"`

`= 10/(10 + 2.5) xx 1`

= 0.8 bar

Hence, the partial pressure of dihydrogen is 0.8 bar.