Molarity is moles of solute per litre of solution, so for ascorbic acid it is the mass divided by 176.124 g/mol and then by the volume in litres. One gram in 100 mL is 0.056778 mol/L; the same gram in a litre is 0.0056778 mol/L; and 176.124 g in a litre is a 1 M solution. Enter a mass and a volume and the calculator does both divisions, and also reports the strength as g/L and % w/v.
The figure comes from the formula. Ascorbic acid is 6 × 12.011 (C) + 8 × 1.008 (H) + 6 × 15.999 (O), which is 176.124 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: 6 of the 20 atoms in a formula unit are oxygen, and they account for 95.994 g of the 176.124 g, or 54.5% by mass. The derivation table below breaks the whole molecule down element by element.
The volume in the denominator is the volume of the finished solution, not the volume of water you started with. Dissolving 176.124 g of a solid adds a little volume of its own, so a solution made up to the mark in a volumetric flask is at the molarity you calculated while the same solid stirred into a litre of water is slightly weaker. At dilute strengths the difference is negligible; at 1 M and above it is not.
Vitamin C, also used as a dough conditioner and an antioxidant. Solutions oxidise in air and light, so they are made fresh for assays. At 176.124 g/mol it is heavier than 10 of the 12 acids covered here, and that ranking matters more than it looks: tartaric acid has a molar mass of 150.086 g/mol, so a gram of it contains 17.3% more formula units than a gram of ascorbic 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 176.124 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
m- The mass of ascorbic acid dissolved, in grams
V- The final volume of the solution, in millilitres
176.124- The molar mass of ascorbic acid in g/mol, derived from its formula
c- The concentration in moles per litre
How it works, step by step
- Enter the mass of ascorbic acid you dissolved, in grams.
- Enter the final volume of the solution in millilitres.
- The mass is divided by 176.124 g/mol and then by the volume in litres.
- The result is molarity in mol/L, with mmol/L, g/L and % w/v given alongside.
Worked examples
1 g of ascorbic acid made up to 100 mL
1 g is 0.00567782 mol. Divided by 0.1 L that is 0.0567782 mol/L, or 56.778 mmol/L. The same solution is 10 g/L and 1% w/v — four ways of writing one strength.
5 g of ascorbic acid made up to 500 mL
5 g is 0.0283891 mol. Divided by 0.5 L that is 0.0567782 mol/L, or 56.778 mmol/L. The same solution is 10 g/L and 1% w/v — four ways of writing one strength.
25 g of ascorbic acid made up to 1000 mL
25 g is 0.141945 mol. Divided by 1 L that is 0.141945 mol/L, or 141.95 mmol/L. The same solution is 25 g/L and 2.5% w/v — four ways of writing one strength.
How to read your score
Frequently asked questions
What is the molar mass of ascorbic acid (C6H8O6)?
It is 176.124 g/mol. That is the sum of the standard atomic weights of every atom in the formula: 6 × 12.011 (C) + 8 × 1.008 (H) + 6 × 15.999 (O). One mole of ascorbic acid therefore weighs 176.124 g, and a gram of it is 5.6778 mmol.
What percentage of ascorbic acid is oxygen?
54.5% by mass. Each formula unit contains 6 oxygen atoms contributing 95.994 g of the 176.124 g total, so 100 g of ascorbic acid contains 54.5 g of oxygen and a kilogram contains 545.04 g of it.
How do I calculate the molarity of a ascorbic acid solution?
Divide the mass in grams by 176.124 g/mol to get moles, then divide by the volume of solution in litres. Both divisions are in the calculator: enter grams and millilitres and it reports mol/L.
What is the molarity of 1 g of ascorbic acid in 100 mL?
0.0567782 mol/L, or 56.778 mmol/L. The same gram in 250 mL gives 0.0227113 mol/L and in a litre 0.00567782 mol/L, since molarity falls in inverse proportion to the volume.
Is molarity per litre of water or per litre of solution?
Per litre of finished solution. That is why volumetric glassware is filled to a mark after the solid has dissolved rather than measured out first. Molality, which is per kilogram of solvent, is the quantity defined the other way and is not what this page computes.
How do mol/L, g/L and % w/v relate for ascorbic acid?
One mol/L of ascorbic acid is 176.124 g/L, which is 17.612% w/v. Going the other way, 1% w/v is 10 g/L and therefore 0.056778 mol/L. All three describe the same solution.
Molarity of ascorbic acid by mass and volume
| Element | Atoms | Atomic weight | Contribution (g/mol) | By mass |
|---|---|---|---|---|
| Oxygen (O) | 6 | 15.999 | 95.994 | 54.5% |
| Carbon (C) | 6 | 12.011 | 72.066 | 40.92% |
| Hydrogen (H) | 8 | 1.008 | 8.064 | 4.579% |
| Total — one mole of ascorbic acid | 176.124 | 100% |
Standard atomic weights, IUPAC 2021. The contribution column is atoms × atomic weight, and the total is the molar mass this page uses: 176.124 g/mol.
| Solute | in 100 mL | in 250 mL | in 500 mL | in 1 L |
|---|---|---|---|---|
| 10 mg | 0.00056778 | 0.00022711 | 0.00011356 | 0.000057 |
| 50 mg | 0.0028389 | 0.0011356 | 0.00056778 | 0.00028389 |
| 100 mg | 0.0056778 | 0.0022711 | 0.0011356 | 0.00056778 |
| 250 mg | 0.014195 | 0.0056778 | 0.0028389 | 0.0014195 |
| 500 mg | 0.028389 | 0.011356 | 0.0056778 | 0.0028389 |
| 1 g | 0.056778 | 0.022711 | 0.011356 | 0.0056778 |
| 2 g | 0.11356 | 0.045423 | 0.022711 | 0.011356 |
| 5 g | 0.28389 | 0.11356 | 0.056778 | 0.028389 |
| 10 g | 0.56778 | 0.22711 | 0.11356 | 0.056778 |
| 25 g | 1.4195 | 0.56778 | 0.28389 | 0.14195 |
| 50 g | 2.8389 | 1.1356 | 0.56778 | 0.28389 |
| 100 g | 5.6778 | 2.2711 | 1.1356 | 0.56778 |
All figures in mol/L. Each is the mass divided by 176.124 g/mol and then by the volume in litres, so the columns differ only by that volume.
| Compound | Formula | Molar mass (g/mol) | Millimoles in 1 g |
|---|---|---|---|
| Oxalic acid | C2H2O4 | 90.034 | 11.107 |
| Lactic acid | C3H6O3 | 90.078 | 11.101 |
| Phosphoric acid | H3PO4 | 97.99376 | 10.205 |
| Sulfuric acid | H2SO4 | 98.072 | 10.197 |
| Tartaric acid | C4H6O6 | 150.086 | 6.6628 |
| Ascorbic acid (this page) | C6H8O6 | 176.124 | 5.6778 |
| Citric acid | C6H8O7 | 192.123 | 5.205 |
Ordered by molar mass. The last column is 1000/M, which is the number a weighed gram actually gives you.