Molar MassMolar mass of manganese(IV) oxide (MnO2)
The molar mass of manganese(IV) oxide, MnO2, is 86.94 g/mol. One mole of it, which is 6.022 × 1023 formula units, has a mass of 86.94 grams.
86.94 g/mol
54.938 + 2 × 15.999 = 86.936 · 3 atoms in the formula · also called manganese dioxide
About manganese(IV) oxide
Manganese(IV) oxide is a black powder used in dry cells and as the catalyst when hydrogen peroxide or potassium chlorate is decomposed to give oxygen.
Other names: manganese dioxide.
The working
The formula MnO2 has 1 manganese 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 |
|---|---|---|---|---|
| Manganese (Mn) | 1 | 54.938 | 54.938 | 63.19% |
| Oxygen (O) | 2 | 15.999 | 31.998 | 36.81% |
54.938 + 2 × 15.999 = 86.936 g/mol
With the rounded atomic masses used in many school books (Mn = 55, O = 16) the answer is 87 g/mol. The difference from 86.94 is too small to matter in most school sums.
Percentage composition
By mass, MnO2 is 63.19% manganese and 36.81% oxygen. The largest share comes from manganese. In a 100 g sample there are 63.2 g of manganese and 36.8 g of oxygen.
Notice that oxygen has more atoms in the formula (2) than manganese (1), 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 25 g of MnO2? Divide the mass by the molar mass: 25 ÷ 86.94 = 0.2876 mol.
Moles to grams. What is the mass of 0.1 mol of MnO2? Multiply: 0.1 × 86.94 = 8.694 g.
Counting particles. 25 g contains 0.2876 mol × 6.022 × 1023 = 1.732 × 1023 formula units.
Quick conversion tables
| Amount | Mass |
|---|---|
| 0.1 mol | 8.694 g |
| 0.5 mol | 43.47 g |
| 1 mol | 86.94 g |
| 2 mol | 173.9 g |
| 5 mol | 434.7 g |
| Mass | Moles |
|---|---|
| 1 g | 0.0115 mol |
| 10 g | 0.115 mol |
| 100 g | 1.15 mol |
| 1 kg | 11.5 mol |
For other amounts use the grams and moles converter.
Questions people ask
What is the molar mass of MnO2?
The molar mass of manganese(IV) oxide (MnO2) is 86.94 g/mol, or 86.936 g/mol before rounding, using IUPAC abridged atomic weights.
How many moles are in 100 g of MnO2?
100 ÷ 86.94 = 1.15 mol.
What is the mass of one formula unit of MnO2?
Divide the molar mass by the Avogadro constant: 86.94 ÷ 6.022 × 1023 = 1.444 × 10-22 g.
What is the percentage of manganese in MnO2?
Manganese makes up 63.19% of the mass of MnO2: 1 × 54.938 ÷ 86.936 × 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.