Helium gas taken from a nuclear experiment contains the isotopes 3He and 4He.One mole of the gas weighs 3.25 g and has a pressure of 1 atm.What is the partial pressure of 3He?

Question

samigupta8 · Answer

@priyar

priyar · Answer

Ptotal = XaPa +XbPb where a- 3He and b-4He

samigupta8 · Answer

Bt we don't know the mole fraction

samigupta8 · Answer

And even the partial pressure of other isotope is also not given

priyar · Answer

use this to find x: (x->wt. of a )
$$\frac{ x }{ 3 } + \frac{ 3.25-x }{ 4  } =1 $$
after u get x you can easily find the mole fraction of each.. that is Xa and Xb.. And you are already given Ptotal..

priyar · Answer

are you sure Pa is not given?

samigupta8 · Answer

Yep !

kainui · Answer

I don't see how you can solve this without more information, since I'm looking at for 3 and 4 referring to the He isotopes respectively,

$$1= X_3+X_4$$$$P_{tot} = P_3X_3 + P_4X_4 $$$$M_{tot} = M_3X_3 + M_4X_4 $$
Essentially you have 3 equations and 4 unknowns, so we need one more bit of information.

Is there any other info, can you make sure you have copied the question down exactly as it is written and have not left out any other information?

samigupta8 · Answer

Sir ! I have checked it but they didn't give more information of the question than the posted one...

samigupta8 · Answer

And btw...the formula u all are giving is Raoult's law for mixing of two ideal solution

kainui · Answer

Is Raoult's law bad?

samigupta8 · Answer

Think so ! Bcoz after all it is used for ideal solutions of liquids and not gases...