Gas Laws question: same pressure for 5 gases, determine largest number of moles, Please help!

Question

You have a container filled with a mixture of five gases: He, H₂, O₂, CO₂, and N₂. The pressure of each gas is identical, resulting in the overall pressure of 100.0 kPa.                                                                                           

 a.  What is the partial pressure of each gas?                                                                                

 b.  Which gas has the largest number of moles?

I think part a should just be 20,0 kPa, but I'm not sure how to determine the moles with just that information.

Answer 1

Yes, you are correct that each gas has a partial pressure of 20 kPa. To determine moles, you refer to Dalton’s law and consider that the partial pressure of each gas equals the mole fraction of that gas x total pressure. Since the partial pressure of each gas is the same, the mole fraction of each would also be the same. Thus moles of each are the same.

P_i = X_iP_T

X_i = P_i / P_T = 20 / 100 = 0.2

0.2 x100 = 20 moles