Calculating number of moles, density, and mass?

Use the following information about air trapped in a flask:





The air is 82.0% nitrogen and 18.0% oxygen (by number of moles).


Pressure = 0.984 atm


Temp = 25.1 deg. C


Volume = 1.039 L





R = 0.0821 L*atm/mol*K


N = 14.01 g/mol


O = 16.00 g/mol





a)How many moles of gas are there in the flask?


b)How many moles of nitrogen gas are there?


c)How many moles of oxygen gas are there?


d)What is the overall density of the air?


e)What is the mass of air in the flask?





You don't have to answer all of these, but anything would help. Thanks.

Calculating number of moles, density, and mass?
a). n = pV/RT


b.) moles of gas (n from a) * nitrogen(.78)


c.) moles of gas(n from a) * oxygen (.22)


d.)( answer b*(the weight of nitrogen(28.02))) + ( answer a*(the weight of oxygen(32)))


e.) answer d * volume (1.039)
Reply:OMG we just had a test on this stuff... why can't I remember?