Question

A mixture of $2g$ hydrogen and $64g$ oxygen exerts a pressure of $3atm$. The partial pressure of oxygen will be:

Answer 1

The molar masses of hydrogen and oxygen are 2 g/mol and 64 g/mol respectively.
The number of moles of hydrogen $=\frac{2g}{2g/mol}=1mol$.
The number of moles of oxygen $=\frac{64g}{32g/mol}=2mol$.
The mole fraction of oxygen $=\frac{2}{2+1}=\frac{2}{3}$
The partial pressure of oxygen is the product of its mole fraction and total pressure. It is $\frac{2}{3}\times 3atm=2atm$