Qual è la formula molecolare dell'aceto?

Vinegar isn't a single chemical substance, but a mixture in the form of a solution, so there are several different substances present each with their own formula.

The most significant substance other than the water it is all dissolved in is called ethanoic acid (old name acetic acid) and this gives vinegar it's smell and acidity.

The molecular formula for ethanoic acid is #C_2H_4O_2# but formulae like this are ambiguous. Other substances might have the same number if each atom but arranged differently in the molecule, so it us better to use a structural formula: #CH_3COOH#