To calculate the molecular weight of diethyl ether, determine the molecular formula, find the atomic weight of each atom, multiply the atomic weight the atom by the number of atoms of the element in the molecular formula, and add the results. Consult a periodic table of the elements to determine atomic weights.
- Determine the molecular formula
Use the name of the compound to determine its molecular formula. Diethyl ether is two ethyl groups joined with a single oxygen atom. Each ethyl group contributes two carbon atoms and five hydrogen atoms to the molecule, giving a molecular formula of C4H10O.
- Determine the atomic masses of the elements
Use the periodic table of the elements to find the atomic weight of each atom represented in the molecule. Carbon has an atomic weight of 12.01, oxygen has an atomic weight of 16.00, and hydrogen's atomic weight is 1.01.
- Calculate the atomic mass units each element contributes
Multiply the molecular weight of carbon, 12.01, by the number of carbon atoms, four. It provides 48.04 atomic mass units to the molecule. Repeat with hydrogen, atomic weight of 1.01, to provide 10.10 units. The single oxygen contributes 16.00 units.
- Add the atomic weights
Find molecular weights by adding the masses contributed by each element. For diethyl ether, the molecular weight is 48.04 + 10.10 + 16.00 or 74.14 atomic mass units or 74.14 grams per mole.