An oxide of nitrogen contains 63.1% oxygen and has a molar mass of 76.0 g/mol. What is the molecular formula for this compound?
Take a hypothetical 100-gram sample of the gas and convert each fractional weight to moles.
Divide by the smaller number of moles:
Multiply by 2 to make integer ratios:
N2O3 This is the empirical formula.
N2O3 has a molar mass of 76.0117 , so it is molecular formula too.