The molecular weight of Acetic anhydride ((CH₃CO)₂O) is 102.089.

To calculate molecular weight of any compound, the first step is to know the constituent atoms and their number in that particular compound. Then calculate the total weight of each atom by multiplying its atomic weight by its number. The sum of total weight of all constituent atoms will be the molecular weight of the compound. Note that the value of atomic weight may differ slightly from different sources.

CALCULATION PROCEDURE: Acetic anhydride ((CH₃CO)₂O) Molecular Weight Calculation

Step 1: Find out the chemical formula and determine constituent atoms and their number in a Acetic anhydride molecule.
From the chemical formula, you will know different atoms and their number in a Acetic anhydride molecule. Chemical formula of Acetic anhydride is C₄H₆O₃. From the chemical formula of Acetic anhydride, you can find that one molecule of Acetic anhydride has four Carbon (C) atoms, six Hydrogen (H) atoms and three Oxygen (O) atoms.

Step 2: Find out atomic weights of each atom (from periodic table).

Atomic weight of Carbon (C): 12.0107 (Ref: Jlab-ele006)
Atomic weight of Hydrogen (H) : 1.008 (Ref: Lanl-1)
Atomic weight of Oxygen (O) : 15.9994 (Ref: Jlab-ele008)

Step 3: Calculate the total weight of each atom present in a Acetic anhydride molecule by multiplying its atomic weight by its number.

Number of Carbon atoms in Acetic anhydride: 4
Atomic weight of Carbon: 12.0107
Total weight of Carbon atoms in Acetic anhydride: 12.0107 x 4 = 48.0428

Number of Hydrogen atoms in Acetic anhydride: 6
Atomic weight of Hydrogen: 1.008
Total weight of Hydrogen atoms in Acetic anhydride: 1.008 x 6 = 6.048

Number of Oxygen atoms in Acetic anhydride: 3
Atomic weight of Oxygen: 15.9994
Total weight of Oxygen atoms in Acetic anhydride: 15.9994 x 3 = 47.9982

Step 4: Calculate the molecular weight of Acetic anhydride by adding up the total weight of all atoms.

Molecular weight of Acetic anhydride: 48.0428 (Carbon) + 6.048 (Hydrogen) + 47.9982 (Oxygen) = 102.089

So the molecular weight of Acetic anhydride is 102.089.

Acetic anhydride ((CH₃CO)₂O) Molecular Weight Calculation

REFERENCES:

• Lanl-1: https://periodic.lanl.gov/1.shtml 
• Pubchem-Hydrogen : https://pubchem.ncbi.nlm.nih.gov/element/Hydrogen 
• Jlab-ele006; https://education.jlab.org/itselemental/ele006.html
• Pubchem-6: https://pubchem.ncbi.nlm.nih.gov/element/6
• Jlab-ele008: https://education.jlab.org/itselemental/ele008.html
• Pubchem-8: https://pubchem.ncbi.nlm.nih.gov/element/8

See also:

• Apiose (C5H10O5) Molecular Weight Calculation