Molar MassMolar mass of silicon dioxide (SiO2)
The molar mass of silicon dioxide, SiO2, is 60.08 g/mol. One mole of it, which is 6.022 × 1023 formula units, has a mass of 60.08 grams.
60.08 g/mol
28.085 + 2 × 15.999 = 60.083 · 3 atoms in the formula · also called silica, quartz
About silicon dioxide
Silicon dioxide is sand and quartz, and the main ingredient of glass. It is a giant network solid with no separate molecules, so the formula shows only the ratio of atoms.
Other names: silica, quartz.
The working
The formula SiO2 has 1 silicon atom and 2 oxygen atoms, 3 atoms in all. Multiply each count by the atomic weight of the element and add:
| Element | Atoms | Atomic weight | Total | Share by mass |
|---|---|---|---|---|
| Silicon (Si) | 1 | 28.085 | 28.085 | 46.74% |
| Oxygen (O) | 2 | 15.999 | 31.998 | 53.26% |
28.085 + 2 × 15.999 = 60.083 g/mol
With the rounded atomic masses used in many school books (Si = 28, O = 16) the answer is 60 g/mol. The difference from 60.08 is too small to matter in most school sums.
Percentage composition
By mass, SiO2 is 46.74% silicon and 53.26% oxygen. The largest share comes from oxygen. In a 100 g sample there are 46.7 g of silicon and 53.3 g of oxygen.
Worked examples
Grams to moles. How many moles are in 40 g of SiO2? Divide the mass by the molar mass: 40 ÷ 60.08 = 0.6657 mol.
Moles to grams. What is the mass of 3 mol of SiO2? Multiply: 3 × 60.08 = 180.2 g.
Counting particles. 40 g contains 0.6657 mol × 6.022 × 1023 = 4.009 × 1023 formula units.
Quick conversion tables
| Amount | Mass |
|---|---|
| 0.1 mol | 6.008 g |
| 0.5 mol | 30.04 g |
| 1 mol | 60.08 g |
| 2 mol | 120.2 g |
| 5 mol | 300.4 g |
| Mass | Moles |
|---|---|
| 1 g | 0.01664 mol |
| 10 g | 0.1664 mol |
| 100 g | 1.664 mol |
| 1 kg | 16.64 mol |
For other amounts use the grams and moles converter.
Questions people ask
What is the molar mass of SiO2?
The molar mass of silicon dioxide (SiO2) is 60.08 g/mol, or 60.083 g/mol before rounding, using IUPAC abridged atomic weights.
How many moles are in 100 g of SiO2?
100 ÷ 60.08 = 1.664 mol.
What is the mass of one formula unit of SiO2?
Divide the molar mass by the Avogadro constant: 60.08 ÷ 6.022 × 1023 = 9.977 × 10-23 g.
What is the percentage of oxygen in SiO2?
Oxygen makes up 53.26% of the mass of SiO2: 2 × 15.999 ÷ 60.083 × 100.
Which values? This site uses the abridged standard atomic weights published by IUPAC (CIAAW), read on 12 November 2026. Your textbook or question paper may round them differently, for example H = 1 and O = 16, so its answer can differ slightly. In an exam, use the values the paper gives.