Found the right answer:

"Hi, I found the right answer: N2O4.

Here is my works:

1. I found the mass of each gas in the compound using the given % by mass.

mass of N= .304*5.25= 1.596g N

mass of O= 5.25 - 1.596= 3.654g O

2. Mass-Mole conversion:

1.596g N* 1mol of N/ 14.01g of N = 0.1139 mol N

3.654g O* 1mol of O/ 16g of O = 0.2284 mol of O

3. Writing the Emperical Formula:

0.1139/0.1139= 1

0.1139/0.2284= 2

=> NO2

Emp. Formulas mass= 46.01g

4. Find the Molar Mass:

M= m*RT/PV

=> M= {5.25g*0.0821(L*atm/K*mol)*269K}/(1.26atm*1L)

M= 92.02g

5. Find the Multiplier (x)

x= Molar mass/Emp.Formula mass= 92.02g/46.01g

x= 2

Molecular Formula:

(NO2)*2 => N2O4" - iconwin