Question

Equal masses of ethane and hydrogen are mixed at 25 degrees what is pressure?

Answer 1

Molar mass of methane = 16.042g mol-1 
Molar mass of oxygen = 32.00 g mol-1 

Therefore if say, 32g of methane and 32g of oxygen mixed,

there is 2 moles of methane and 1 moles of oxygen. 

n= PV/RT 

pressure is directly proportional to the number of moles 

Oxygen is 1/3 of total number of moles and hence it exerts 1/3 of the total pressure