For one mole of hydrogen, H, the atomic mass is 1 g per mole. Hydrogen contains 1 proton and zero neuton. A neutral atom of hydrigen also contains 1 electron.
The balanced chemical equation of the reaction described above is,
C2H6O + O2 --> H2O + C2H4O2
If we have 3.84 g of oxygen, we divide by its molar mass.
n = (3.54 g Oxygen gas) x (1 mole O2/ 32 g O2)
n = 0.11 moles O2
Using ratio and proportion,
number of moles of ethanol = (0.11 moles O2) x (1 mole C2H6)
= 0.11 moles C2H6
Then, we multiply the calculated value to its molar mass, 46 grams /mol.
mass of ethanol = (0.11 mol) x (46 grams / mol)
= <em>5.06 grams</em>