Moles to grams for uric acid is a multiplication by 168.112 g/mol. A mole weighs 168.112 g, 100 mmol weighs 16.8112 g, 10 mmol weighs 1.68112 g and a millimole is 168.112 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. Uric acid is 5 × 12.011 (C) + 4 × 1.008 (H) + 4 × 14.007 (N) + 3 × 15.999 (O), which is 168.112 g/mol, taking standard atomic weights, and every page here computes that sum rather than quoting it. Carbon makes up the largest share of the mass: 5 of the 16 atoms in a formula unit are carbon, and they account for 60.055 g of the 168.112 g, or 35.72% 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 end point of purine metabolism and the crystal that causes gout. Barely soluble in water, which is precisely why it crystallises in joints. At 168.112 g/mol it is heavier than 14 of the 21 organic compounds covered here, and that ranking matters more than it looks: paracetamol has a molar mass of 151.165 g/mol, so a gram of it contains 11.2% more formula units than a gram of uric acid. Weigh by mass and you are not weighing equal amounts of substance.
Purity is the usual gap between the calculation and the balance. A reagent sold at 98% means 3.3622 g of a nominal 168.112 g is something else, so for exact work you divide the weighed mass by the assay figure on the certificate. For most purposes the difference is smaller than the error in reading the meniscus, but it is systematic rather than random, so it does not average out.
The formula
n- The amount of uric acid you need, in moles
168.112- The molar mass of uric 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 168.112 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 uric acid in grams
5 mmol × 168.112 g/mol = 0.84056 g, which is 840.56 mg. Doubling the amount doubles the mass to 1.68112 g, because the relationship is a plain proportion once the molar mass is fixed.
250 mmol of uric acid in grams
250 mmol × 168.112 g/mol = 42.028 g, which is 42,028 mg. Doubling the amount doubles the mass to 84.056 g, because the relationship is a plain proportion once the molar mass is fixed.
2 mol of uric acid in grams
2 mol × 168.112 g/mol = 336.224 g, which is 336,224 mg. Doubling the amount doubles the mass to 672.448 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 uric acid (C5H4N4O3)?
It is 168.112 g/mol. That is the sum of the standard atomic weights of every atom in the formula: 5 × 12.011 (C) + 4 × 1.008 (H) + 4 × 14.007 (N) + 3 × 15.999 (O). One mole of uric acid therefore weighs 168.112 g, and a gram of it is 5.9484 mmol.
What percentage of uric acid is carbon?
35.72% by mass. Each formula unit contains 5 carbon atoms contributing 60.055 g of the 168.112 g total, so 100 g of uric acid contains 35.72 g of carbon and a kilogram contains 357.23 g of it.
How many grams is one mole of uric acid?
168.112 g, by definition of the molar mass. Two moles is 336.224 g and half a mole is 84.056 g.
How many grams is 0.1 mol, and how many milligrams is 1 mmol?
0.1 mol of uric acid is 16.8112 g. One millimole is 168.112 mg and one micromole is 168.112 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 1.681 mg of uric acid, weigh 16.81 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, C5H4N4O3, at 168.112 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 uric acid
| Element | Atoms | Atomic weight | Contribution (g/mol) | By mass |
|---|---|---|---|---|
| Carbon (C) | 5 | 12.011 | 60.055 | 35.72% |
| Nitrogen (N) | 4 | 14.007 | 56.028 | 33.33% |
| Oxygen (O) | 3 | 15.999 | 47.997 | 28.55% |
| Hydrogen (H) | 4 | 1.008 | 4.032 | 2.398% |
| Total — one mole of uric acid | 168.112 | 100% |
Standard atomic weights, IUPAC 2021. The contribution column is atoms × atomic weight, and the total is the molar mass this page uses: 168.112 g/mol.
| Wanted | Weigh (g) | Weigh (mg) | With 2% over (g) |
|---|---|---|---|
| 1 µmol | 0.000168112 | 0.168112 | 0.000171474 |
| 10 µmol | 0.00168112 | 1.68112 | 0.00171474 |
| 100 µmol | 0.0168112 | 16.8112 | 0.0171474 |
| 1 mmol | 0.168112 | 168.112 | 0.171474 |
| 10 mmol | 1.68112 | 1681.12 | 1.71474 |
| 50 mmol | 8.4056 | 8405.6 | 8.57371 |
| 100 mmol | 16.8112 | 16,811.2 | 17.1474 |
| 250 mmol | 42.028 | 42,028 | 42.8686 |
| 500 mmol | 84.056 | 84,056 | 85.7371 |
| 750 mmol | 126.084 | 126,084 | 128.606 |
| 1 mol | 168.112 | 168,112 | 171.474 |
| 2 mol | 336.224 | 336,224 | 342.948 |
| 5 mol | 840.56 | 840,560 | 857.371 |
| 10 mol | 1681.12 | 1681120.000000 | 1714.74 |
Weigh is the amount multiplied by 168.112 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 |
|---|---|---|---|
| Octane | C8H18 | 114.232 | 8.7541 |
| Tris base | C4H11NO3 | 121.136 | 8.2552 |
| Paracetamol | C8H9NO2 | 151.165 | 6.6153 |
| Uric acid (this page) | C5H4N4O3 | 168.112 | 5.9484 |
| Glucose | C6H12O6 | 180.156 | 5.5507 |
| Aspirin | C9H8O4 | 180.159 | 5.5507 |
| Caffeine | C8H10N4O2 | 194.194 | 5.1495 |
Ordered by molar mass. The last column is 1000/M, which is the number a weighed gram actually gives you.