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. 

Answer 2

Pressure of the gas mixture = 1 bar

Let us consider 100g of the mixture

So ,mass of hydrogen in the mixture  = 20 g

& mass of oxygen in the mixture = 80 g

Using the respective molar masses, we get

  n_H = 20/ 2  = 10 mol

. n_O = 80 / 32 = 2.5 mol

Then, p_H = X_H x P_total

= (n_H / n_{H +} n_O) x P _total  

= (10 / 10 + 2.5 ) x  1 

= 0.8 bar

Hence, the partial pressure of dihydrogen is 0.8 bar.