The molar mass of sulfuric acid (H2SO4) is 98.072 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 |
|---|---|---|---|---|
| Hydrogen (H) | 2 | 1.0080 | 2.016 | 2.06% |
| Oxygen (O) | 4 | 15.999 | 63.996 | 65.25% |
| Sulfur (S) | 1 | 32.06 | 32.060 | 32.69% |
| Total | 7 | 98.072 | 100.00% |
2.016 + 63.996 + 32.060 = 98.072 g/mol
Grams and moles
25 g of sulfuric acid is 0.2549 mol, because 25 ÷ 98.072 = 0.2549.
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: 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; sulfur is 32.06, and really lies between 32.059 and 32.076.
More sulfuric acid is produced by tonnage than any other industrial chemical. It weighs 98.072 g/mol, with oxygen dominating at 65.25%, sulfur at 32.69%, and the two acidic hydrogens accounting for barely 2% of the weight despite being the entire point of the molecule.
That last figure trips up titration work. Sulfuric acid is diprotic, releasing two protons per molecule, so one mole neutralises two moles of sodium hydroxide. The mass ratio and the mole ratio pull in opposite directions, and working in grams instead of moles is the dependable way to get such a question wrong.
You will also meet 98.079 quoted in place of 98.072. The difference traces to sulfur, whose atomic weight IUPAC revised from 32.065 to a conventional value of 32.06. Both figures are internally consistent with the table they came from, and neither is an error.