Moles to grams for nitric acid is a multiplication by 63.012 g/mol. A mole weighs 63.012 g, 100 mmol weighs 6.3012 g, 10 mmol weighs 0.63012 g and a millimole is 63.012 mg. Those four figures cover most of what gets weighed out in practice, and the table below extends them from a micromole up to ten moles.
The figure comes from the formula. Nitric acid is 1.008 (H) + 14.007 (N) + 3 × 15.999 (O), which is 63.012 g/mol, taking standard atomic weights, and every page here computes that sum rather than quoting it. Oxygen makes up the largest share of the mass: 3 of the 5 atoms in a formula unit are oxygen, and they account for 47.997 g of the 63.012 g, or 76.17% by mass. The derivation table below breaks the whole molecule down element by element.
Two habits make the weighed mass match the calculation. Weigh into a container you have tared rather than onto paper, because what stays behind on paper is a real loss — on a 100 mg weighing it is easily a percent. And when the target is under about 20 mg, weigh ten times that and dilute, since the absolute error of the balance does not shrink with the sample.
The acid for nitration and metal digestion. Concentrated is 68% w/w, near 15.8 mol/L, and it stains skin yellow on contact. At 63.012 g/mol it is heavier than 4 of the 12 acids covered here, and that ranking matters more than it looks: boric acid has a molar mass of 61.831 g/mol, so a gram of it contains 1.91% more formula units than a gram of nitric acid. Weigh by mass and you are not weighing equal amounts of substance.
One more step applies if you are starting from a concentrated bottle. Concentrated acids are labelled as a percentage by weight together with a density, not as a molarity, so getting to mol/L means multiplying density by that percentage and dividing by 63.012 g/mol. A page like this one gives you the last of those three numbers; the first two are on the bottle, and they vary between grades.
The formula
n- The amount of nitric acid you need, in moles
63.012- The molar mass of nitric acid in g/mol, derived from its formula
m- The mass to weigh out, in grams
How it works, step by step
- Enter the amount you need, in moles.
- It is multiplied by 63.012 g/mol.
- The result is the mass to weigh out, also given in milligrams.
- Weigh into a tared container; anything left in the boat is a real loss from the amount you calculated.
Worked examples
5 mmol of nitric acid in grams
5 mmol × 63.012 g/mol = 0.31506 g, which is 315.06 mg. Doubling the amount doubles the mass to 0.63012 g, because the relationship is a plain proportion once the molar mass is fixed.
250 mmol of nitric acid in grams
250 mmol × 63.012 g/mol = 15.753 g, which is 15,753 mg. Doubling the amount doubles the mass to 31.506 g, because the relationship is a plain proportion once the molar mass is fixed.
2 mol of nitric acid in grams
2 mol × 63.012 g/mol = 126.024 g, which is 126,024 mg. Doubling the amount doubles the mass to 252.048 g, because the relationship is a plain proportion once the molar mass is fixed.
How to read your score
Frequently asked questions
What is the molar mass of nitric acid (HNO3)?
It is 63.012 g/mol. That is the sum of the standard atomic weights of every atom in the formula: 1.008 (H) + 14.007 (N) + 3 × 15.999 (O). One mole of nitric acid therefore weighs 63.012 g, and a gram of it is 15.87 mmol.
What percentage of nitric acid is oxygen?
76.17% by mass. Each formula unit contains 3 oxygen atoms contributing 47.997 g of the 63.012 g total, so 100 g of nitric acid contains 76.17 g of oxygen and a kilogram contains 761.71 g of it.
How many grams is one mole of nitric acid?
63.012 g, by definition of the molar mass. Two moles is 126.024 g and half a mole is 31.506 g.
How many grams is 0.1 mol, and how many milligrams is 1 mmol?
0.1 mol of nitric acid is 6.3012 g. One millimole is 63.012 mg and one micromole is 63.012 µg, which is the range most bench work sits in.
How do I weigh out an amount too small for my balance?
Weigh a larger mass and dilute it. To get 0.6301 mg of nitric acid, weigh 6.301 mg into 100 mL, then take 10 mL of that: the absolute error of the balance stays the same while the amount delivered falls by a factor of ten.
Should I use the hydrate or the anhydrous molar mass?
This page is the anhydrous form, HNO3, at 63.012 g/mol. If your jar is the other form the molar mass differs and so will every mass you weigh, so check the label before using the figure. Salts that are sold as hydrates weigh more per mole because the water is part of the crystal.
Moles to grams reference for nitric acid
| Element | Atoms | Atomic weight | Contribution (g/mol) | By mass |
|---|---|---|---|---|
| Oxygen (O) | 3 | 15.999 | 47.997 | 76.17% |
| Nitrogen (N) | 1 | 14.007 | 14.007 | 22.23% |
| Hydrogen (H) | 1 | 1.008 | 1.008 | 1.6% |
| Total — one mole of nitric acid | 63.012 | 100% |
Standard atomic weights, IUPAC 2021. The contribution column is atoms × atomic weight, and the total is the molar mass this page uses: 63.012 g/mol.
| Wanted | Weigh (g) | Weigh (mg) | With 2% over (g) |
|---|---|---|---|
| 1 µmol | 0.000063 | 0.063012 | 0.000064 |
| 10 µmol | 0.00063012 | 0.63012 | 0.000642722 |
| 100 µmol | 0.0063012 | 6.3012 | 0.00642722 |
| 1 mmol | 0.063012 | 63.012 | 0.0642722 |
| 10 mmol | 0.63012 | 630.12 | 0.642722 |
| 50 mmol | 3.1506 | 3150.6 | 3.21361 |
| 100 mmol | 6.3012 | 6301.2 | 6.42722 |
| 250 mmol | 15.753 | 15,753 | 16.0681 |
| 500 mmol | 31.506 | 31,506 | 32.1361 |
| 750 mmol | 47.259 | 47,259 | 48.2042 |
| 1 mol | 63.012 | 63,012 | 64.2722 |
| 2 mol | 126.024 | 126,024 | 128.544 |
| 5 mol | 315.06 | 315,060 | 321.361 |
| 10 mol | 630.12 | 630,120 | 642.722 |
Weigh is the amount multiplied by 63.012 g/mol. The last column carries a 2% allowance, which is what you take when some of the solid will be left in the weighing boat.
| Compound | Formula | Molar mass (g/mol) | Millimoles in 1 g |
|---|---|---|---|
| Formic acid | CH2O2 | 46.025 | 21.727 |
| Acetic acid | CH3COOH | 60.052 | 16.652 |
| Boric acid | H3BO3 | 61.831 | 16.173 |
| Nitric acid (this page) | HNO3 | 63.012 | 15.87 |
| Oxalic acid | C2H2O4 | 90.034 | 11.107 |
| Lactic acid | C3H6O3 | 90.078 | 11.101 |
| Phosphoric acid | H3PO4 | 97.99376 | 10.205 |
Ordered by molar mass. The last column is 1000/M, which is the number a weighed gram actually gives you.