The molar mass of silver nitrate, AgNO3, is 169.8722 g/mol. That single number is what connects a mass you can weigh to an amount of substance you can react: one mole is 169.8722 g, and a gram of it is 3.545e+21 formula units. The calculator turns any weighed mass into that count, and reports the amount in moles, millimoles and the mass of a single formula unit alongside it.
The figure comes from the formula. Silver nitrate is 107.868 (Ag) + 14.007 (N) + 3 × 15.999 (O), which is 169.8722 g/mol, taking standard atomic weights, and every page here computes that sum rather than quoting it. Silver makes up the largest share of the mass: 1 of the 5 atoms in a formula unit is silver, and they account for 107.868 g of the 169.8722 g, or 63.5% by mass. The derivation table below breaks the whole molecule down element by element.
The numbers a bench actually uses sit at the millimole scale. One millimole of silver nitrate is 169.872 mg and one micromole is 169.872 µg, so a balance reading to a milligram places you within 5.887 µmol. A single formula unit weighs 2.8208e-22 g, which is why the count in the gauge runs into the sextillions for any mass you can see.
The reagent for chloride tests and the silver source in mirroring and photography. Solutions darken in light and stain skin permanently. At 169.8722 g/mol it is heavier than 23 of the 34 salts covered here, and that ranking matters more than it looks: potassium iodide has a molar mass of 166.0028 g/mol, so a gram of it contains 2.33% more formula units than a gram of silver nitrate. 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 3.3974 g of a nominal 169.8722 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
m- The mass of silver nitrate in grams
169.8722- The molar mass of silver nitrate in g/mol, derived from its formula
N- The number of formula units that mass contains
How it works, step by step
- Enter a mass of silver nitrate in grams.
- It is divided by the molar mass, 169.8722 g/mol, giving the amount in moles.
- That amount is multiplied by the Avogadro constant, 6.02214076 × 10²³ per mole, to give the number of formula units.
- The panel also reports the amount in moles and millimoles and the mass of one formula unit.
Worked examples
0.5 g of silver nitrate as a molecule count
0.5 g divided by 169.8722 g/mol is 0.00294339 mol, and multiplying by the Avogadro constant gives 1.773e+21 formula units of silver nitrate. The same mass is 2.9434 mmol, which is the figure a reaction is actually planned in.
5 g of silver nitrate as a molecule count
5 g divided by 169.8722 g/mol is 0.0294339 mol, and multiplying by the Avogadro constant gives 1.773e+22 formula units of silver nitrate. The same mass is 29.434 mmol, which is the figure a reaction is actually planned in.
50 g of silver nitrate as a molecule count
50 g divided by 169.8722 g/mol is 0.294339 mol, and multiplying by the Avogadro constant gives 1.773e+23 formula units of silver nitrate. The same mass is 294.34 mmol, which is the figure a reaction is actually planned in.
How to read your score
Frequently asked questions
What is the molar mass of silver nitrate (AgNO3)?
It is 169.8722 g/mol. That is the sum of the standard atomic weights of every atom in the formula: 107.868 (Ag) + 14.007 (N) + 3 × 15.999 (O). One mole of silver nitrate therefore weighs 169.8722 g, and a gram of it is 5.8868 mmol.
What percentage of silver nitrate is silver?
63.5% by mass. Each formula unit contains 1 silver atom contributing 107.868 g of the 169.8722 g total, so 100 g of silver nitrate contains 63.5 g of silver and a kilogram contains 635 g of it.
How many molecules are in one gram of silver nitrate?
About 3.545e+21. One gram is 0.00588678 mol, and each mole contains 6.02214076 × 10²³ formula units by definition of the mole, so the count is that constant divided by 169.8722.
How much does a single molecule of silver nitrate weigh?
2.8208e-22 g, which is 169.8722 daltons. It is the molar mass divided by the Avogadro constant, and the number in daltons is numerically the same as the molar mass in g/mol — that equivalence is what makes the mole convenient.
Is molar mass the same as molecular weight?
They are the same number in ordinary use but not the same quantity. Molecular weight, properly relative molecular mass, is a ratio and has no unit: for silver nitrate it is 169.8722. Molar mass carries grams per mole: 169.8722 g/mol. Because the mole is defined so those agree, you can read one off the other.
Why is the molar mass not a whole number?
Because standard atomic weights are averages over the isotopes found in nature. Silver is quoted as 107.8682 rather than a whole number for that reason, and the same applies to the other elements here, which is why silver nitrate comes out at 169.8722 g/mol rather than 170.
Molar mass, composition and mole equivalents of silver nitrate
| Element | Atoms | Atomic weight | Contribution (g/mol) | By mass |
|---|---|---|---|---|
| Silver (Ag) | 1 | 107.8682 | 107.8682 | 63.5% |
| Oxygen (O) | 3 | 15.999 | 47.997 | 28.25% |
| Nitrogen (N) | 1 | 14.007 | 14.007 | 8.246% |
| Total — one mole of silver nitrate | 169.8722 | 100% |
Standard atomic weights, IUPAC 2021. The contribution column is atoms × atomic weight, and the total is the molar mass this page uses: 169.8722 g/mol.
| Amount | Mass (g) | Mass (mg) | Formula units |
|---|---|---|---|
| 1 µmol | 0.000169872 | 0.169872 | 6.022e+17 |
| 10 µmol | 0.00169872 | 1.69872 | 6.022e+18 |
| 100 µmol | 0.0169872 | 16.9872 | 6.022e+19 |
| 1 mmol | 0.169872 | 169.872 | 6.022e+20 |
| 10 mmol | 1.69872 | 1698.72 | 6.022e+21 |
| 50 mmol | 8.49361 | 8493.61 | 3.011e+22 |
| 100 mmol | 16.9872 | 16,987.2 | 6.022e+22 |
| 250 mmol | 42.4681 | 42,468.1 | 1.506e+23 |
| 500 mmol | 84.9361 | 84,936.1 | 3.011e+23 |
| 750 mmol | 127.404 | 127,404 | 4.517e+23 |
| 1 mol | 169.872 | 169,872 | 6.022e+23 |
| 2 mol | 339.744 | 339,744 | 1.204e+24 |
| 5 mol | 849.361 | 849,361 | 3.011e+24 |
| 10 mol | 1698.72 | 1698722.000000 | 6.022e+24 |
Mass is the amount multiplied by 169.8722 g/mol. The last column is that amount multiplied by the Avogadro constant, 6.02214076 × 10²³ per mole.
| Compound | Formula | Molar mass (g/mol) | Millimoles in 1 g |
|---|---|---|---|
| Iron(III) chloride | FeCl3 | 162.195 | 6.1654 |
| Trisodium phosphate | Na3PO4 | 163.9391 | 6.0998 |
| Potassium iodide | KI | 166.0028 | 6.024 |
| Silver nitrate (this page) | AgNO3 | 169.8722 | 5.8868 |
| Gypsum | CaSO4·2H2O | 172.164 | 5.8084 |
| Potassium sulfate | K2SO4 | 174.2526 | 5.7388 |
| Epsom salt | MgSO4·7H2O | 246.466 | 4.0574 |
Ordered by molar mass. The last column is 1000/M, which is the number a weighed gram actually gives you.