The molar mass of acetic acid (C2H4O2) is 60.052 g/mol.
Case matters: CO is carbon monoxide, Co is
cobalt. Brackets and hydrates are fine — try
or
.
| Element | Atoms | Atomic mass | Mass contributed | Percent |
|---|---|---|---|---|
| Carbon (C) | 2 | 12.011 | 24.022 | 40.00% |
| Hydrogen (H) | 4 | 1.0080 | 4.032 | 6.72% |
| Oxygen (O) | 2 | 15.999 | 31.998 | 53.28% |
| Total | 8 | 60.052 | 100.00% |
24.022 + 4.032 + 31.998 = 60.052 g/mol
Grams and moles
25 g of acetic acid is 0.4163 mol, because 25 ÷ 60.052 = 0.4163.
These elements have no single atomic weight. Their isotopic mix varies slightly depending on where on Earth the sample came from, so the figure used here is the conventional value IUPAC publishes for when one number is needed: carbon is 12.011, and really lies between 12.0096 and 12.0116; hydrogen is 1.0080, and really lies between 1.00784 and 1.00811; oxygen is 15.999, and really lies between 15.99903 and 15.99977.
Acetic acid is 60.052 g/mol and it is what makes vinegar sour. Household vinegar runs at about 5% acetic acid by mass, so a 500 mL bottle holds roughly 25 grams, a little over 0.4 moles.
By mass it is 40.00% carbon, 53.28% oxygen and 6.72% hydrogen, a split it shares exactly with glucose. Reduce either formula to its simplest ratio and both land on CH2O, glucose repeating that unit six times where acetic acid repeats it twice. An elemental analysis of the two would return the same answer, and only a molar mass measurement separates them. This pair is the cleanest demonstration of why empirical formulas are not molecular formulas.
The formula is often written CH3COOH rather than C2H4O2, because only one of the four hydrogens is acidic. The other three sit on the methyl carbon and never come off in water. Writing the condensed form loses that distinction, and it is the distinction the whole chemistry of the molecule turns on.