3. nitrogen, when combined with oxygen, can form various oxides. 3.5 g of nitrogen gas is burned in oxygen to form 11.5 g of an oxide of nitrogen.
a) determine the mass of oxygen burned. (hint: the oxide contains only nitrogen and oxygen! )
b)using the data from the experiment, find the percent of nitrogen by mass in the oxide.
c) using the data from the experiment, find the percent of oxygen by mass in the oxide.

the ideal gas law equation is as follows

pv = nrt

where p - pressure

v - volume

n - number of moles

r - universal gas constant

t - temperature

so if the pressure, volume and temperature are already known

we are left with n and r

since r is the universal gas constant that has a known fixed value then r too is known

so we are left with 'n'

once we know temperature volume and pressure

we can find the number of moles of gas present using the ideal gas law equation

this is not my own answer, this is an answer for the same question by the user blahblahmali. i do not claim ownership of this account.