What is the mass of air in a hot air balloon with these conditions?

[jgoff14]

Homework Statement

A hot air balloon has a volume of 2000m^3, and air is always at atmospheric pressure due to large opening. What is the mass of the air if the temp is 120*c. Assume a molecular weight of 28.8g/mol for the air)

Homework Equations

PV=nrt

The Attempt at a Solution

I don't really have one, my class notes on this section are not clear, and the instructor was gone but still expected us to learn it. I don't get it. Please help, this is due tonight at midnight my whole grade hangs in the balance.

 

[mgb_phys]

Does PV=nRT ring any bells?

 

[jgoff14]

come on, some help please!

 

[mgb_phys]

http://en.wikipedia.org/wiki/Pv=nrt

The state of an amount of gas is determined by its pressure, volume, and temperature. The modern form of the equation is:
(PV = nRT )

where p is the absolute pressure of the gas; V is the volume; n is the amount of substance; R is the gas constant; and T is the absolute temperature.

In SI units, p is measured in pascals; V in cubic metres; n in moles; and T in kelvins. R has the value 8.314472 J·K−1·mol−1 in SI units[4]).