Molar mass of water
18.02 g/molH₂O
Molar mass
Molar mass. The mass of one mole in grams: add the atomic mass of every atom in the formula. Masses. Standard atomic masses to two decimals, hydrogen 1.008, every element to uranium. Typing. Ca(OH)2, (NH4)2SO4, CuSO4.5H2O and K4[Fe(CN)6] all work.
18.02g/mol
H₂O
- H× 211.19%
- O× 188.81%
- H2 × 1.0082.016
- O1 × 16.0016.00
- Total18.02 g/mol
Grams, moles, particles
Type any one. The other three fill in. Moles. From grams, particles or litres they are rounded to 3 significant figures first, as in a worked answer. 1 mol = 6.022 × 10²³ particles = 22.7 L of gas at STP (1 bar); 22.4 L at 1 atm.
1 mol of H₂O = 6.022 × 10²³ molecules
At 1 atm (older value): 22.40 L
Add up the atoms
- Hydrogen: 2 × 1.008 = 2.016 g
- Oxygen: 1 × 16.00 = 16.00 g
- Molar mass = 2 × 1.008 + 16.00 = 18.02 g/mol
Share of the mass
- Hydrogen11.19%
- Oxygen88.81%
1 mol of H₂O = 18.02 g
1 g of H₂O = 0.05551 mol
Molar mass of water: quick answers
What is the molar mass of water?
The molar mass of water, H₂O, is 18.02 g/mol. So 1 mol of water has a mass of 18.02 g.
How do you calculate the molar mass of H₂O?
Add the atomic masses of all the atoms: 2 × 1.008 + 16.00 = 18.02 g/mol.
What is the percentage of oxygen in water?
Oxygen is 88.81% of the mass of H₂O: 16.00 g in every 18.02 g. In full: H 11.19%, O 88.81%.