Question

In a room at 24.5 degrees Celsius a balloon is filled with helium to a pressure of 768.0 mmHg. What is the density?

Answer 1

Well, we want the expression `rho_"density"="mass"/"volume"`

Explanation:

And we gots `PV=nRT="mass"/"molar mass"xxRT`..

And thus `Pxx"molar mass"=("mass"xxRT)/V`

And so `rho="mass"/V=(Pxx"molar mass")/(RT)`

And thus....`rho=((768*mm*Hg)/(760*mm*Hg*atm^-1)xx4.003*g*mol^-1)/(0.0821*(L*atm)/(K*mol)xx297.7*K)`

`=0.166*g*L^-1`...and answer with units of density as required.

Will this balloon float?