Molar MassMolar mass of caffeine (C8H10N4O2)
The molar mass of caffeine, C8H10N4O2, is 194.19 g/mol. One mole of it, which is 6.022 × 1023 molecules, has a mass of 194.19 grams.
194.19 g/mol
8 × 12.011 + 10 × 1.0080 + 4 × 14.007 + 2 × 15.999 = 194.194 · 24 atoms in the formula
About caffeine
Caffeine is the stimulant in tea, coffee and cola. Its formula contains four different elements, good practice for a careful atom count.
The working
The formula C8H10N4O2 has 8 carbon atoms, 10 hydrogen atoms, 4 nitrogen atoms and 2 oxygen atoms, 24 atoms in all. Multiply each count by the atomic weight of the element and add:
| Element | Atoms | Atomic weight | Total | Share by mass |
|---|---|---|---|---|
| Carbon (C) | 8 | 12.011 | 96.088 | 49.48% |
| Hydrogen (H) | 10 | 1.0080 | 10.080 | 5.19% |
| Nitrogen (N) | 4 | 14.007 | 56.028 | 28.85% |
| Oxygen (O) | 2 | 15.999 | 31.998 | 16.48% |
8 × 12.011 + 10 × 1.0080 + 4 × 14.007 + 2 × 15.999 = 194.194 g/mol
With the rounded atomic masses used in many school books (C = 12, H = 1, N = 14, O = 16) the answer is 194 g/mol. The difference from 194.19 is too small to matter in most school sums.
Percentage composition
By mass, C8H10N4O2 is 49.48% carbon, 5.19% hydrogen, 28.85% nitrogen and 16.48% oxygen. The largest share comes from carbon. In a 100 g sample there are 49.5 g of carbon, 5.2 g of hydrogen, 28.9 g of nitrogen and 16.5 g of oxygen.
Notice that hydrogen has more atoms in the formula (10) than carbon (8), yet gives a smaller share of the mass. Percentage by mass depends on how heavy each atom is, not only on how many there are.
Worked examples
Grams to moles. How many moles are in 100 g of C8H10N4O2? Divide the mass by the molar mass: 100 ÷ 194.19 = 0.5149 mol.
Moles to grams. What is the mass of 2 mol of C8H10N4O2? Multiply: 2 × 194.19 = 388.4 g.
Counting particles. 100 g contains 0.5149 mol × 6.022 × 1023 = 3.101 × 1023 molecules, and 7.443 × 1024 atoms in all.
Quick conversion tables
| Amount | Mass |
|---|---|
| 0.1 mol | 19.42 g |
| 0.5 mol | 97.1 g |
| 1 mol | 194.2 g |
| 2 mol | 388.4 g |
| 5 mol | 971 g |
| Mass | Moles |
|---|---|
| 1 g | 0.005149 mol |
| 10 g | 0.05149 mol |
| 100 g | 0.5149 mol |
| 1 kg | 5.149 mol |
For other amounts use the grams and moles converter.
Questions people ask
What is the molar mass of C8H10N4O2?
The molar mass of caffeine (C8H10N4O2) is 194.19 g/mol, or 194.194 g/mol before rounding, using IUPAC abridged atomic weights.
How many moles are in 100 g of C8H10N4O2?
100 ÷ 194.19 = 0.5149 mol.
What is the mass of one molecule of C8H10N4O2?
Divide the molar mass by the Avogadro constant: 194.19 ÷ 6.022 × 1023 = 3.225 × 10-22 g.
What is the percentage of carbon in C8H10N4O2?
Carbon makes up 49.48% of the mass of C8H10N4O2: 8 × 12.011 ÷ 194.194 × 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.