Molecular mass of He+MON and He+MMH

[hamzaaaa]

Dear all

I have a case. I have two tanks, one is filled with Helium gas and monomethylhydrazine(MMH) and another tank with Helium gas and Dinitrogentetraoxide(MON). Both tanks are at 47degC so they are in gaseous form.

I want to know what will be the Molecular Mass of the gas. The molecular mass of He=4 g/mol,MMH=46 g/mol and MON=92 g/mol.

So can anyone tell me what will be the molecular mass i should use for computations for (He+MMH, He+MON and He+MMH+MON)

Thanks

 

[Borek]

For some applications you can use weighted average - but calculation requires knowing composition of the mixtures.

 

[hamzaaaa]

But why to take the average and why not the sum of all three?

 

[Borek]

Because some properties scale as the average of the molar mass.

Solve this problem: you mix 0.5 L He and 0.5 L Ar. What is the density of the mixture?

 

[LudusRex]

for your question. The molecular mass of a gas mixture can be calculated by taking the sum of the individual molecular masses of each component, multiplied by their respective mole fractions. In this case, the mole fraction of He will be 1, as it is the only component in both tanks. Therefore, the molecular mass of He+MMH will be (1 x 4) + (0 x 46) = 4 g/mol. Similarly, the molecular mass of He+MON will also be 4 g/mol. For He+MMH+MON, the mole fraction of He will be 0.5, as it is present in both tanks, and the mole fractions of MMH and MON will be 0.5 and 0.5, respectively. Therefore, the molecular mass of He+MMH+MON will be (0.5 x 4) + (0.5 x 46) + (0.5 x 92) = 48 g/mol. I hope this helps with your computations.