The key difference between acetic acid and acetic anhydride molar mass is that acetic acid is a simple carboxylic acid, whereas acetic anhydride is the dehydration product of acetic acid.
Acetic acid is an organic compound having the chemical formula CH3COOH, while acetic anhydride is an organic compound having the chemical formula (CH3CO)2O. We can use acetic acid to produce acetic anhydride molar mass.

What is Acetic Acid?
Acetic acid is an organic compound having the chemical formula CH3COOH. It is the second simplest carboxylic acid. This acid occurs as a colourless liquid having a pungent, vinegar-like odour. Furthermore, acetic acid has a distinctive sour taste as well. This compound has a methyl group attached to a carboxylic acid. It is a weak acid because it dissociates partially in an aqueous solution. The molar mass of acetic acid is 60.05 g/mol. The conjugate base of this acid is an acetate ion. Moreover, the systemic IUPAC name of acetic acid is ethanoic acid.

What is Acetic Anhydride?
Acetic anhydride is an organic compound having the chemical formula (CH3CO)2O. It is also known as ethanoic anhydride. We can abbreviate it as ac2O. Acetic anhydride is the simplest isolable anhydride compound of a carboxylic acid. This substance is widely used as a reagent for organic synthesis processes. It occurs as a colourless liquid having a strong acetic acid odour. This strong odour forms due to the reaction between acetic anhydride molar mass and moisture in the air.
Similar to most other acid anhydride compounds, acetic anhydride is a flexible compound having a nonplanar structure. It has a pi system linkage that forms through the central oxygen atom, which offers a very weak resonance stabilization than the dipole-dipole repulsion between the two carbonyl oxygen atoms. We can produce acetic anhydride by heating potassium acetate with benzoyl chloride. Industrially, it is produced by carbonylation of methyl acetate. However, due to its low cost, laboratories usually do not prepare acetic anhydride for research uses; instead, they purchase it from other suppliers.