Molar Mass of Water (H2O)
Molar Mass of Water is used in gas-law and stoichiometry questions that require clean mole-to-mass conversion. Molar Mass of H₂O is 18.02 g/mol, based on 2 element types, with O contributing the largest share.
For fast checks, use the calculate molar mass, verify element values in the periodic table with molar mass, or explore more molar mass.
Molar Mass of Water is:
18.02 g/mol
Molar Mass of H₂O equals 18.02 g/mol, so 18.02 grams is one mole.
Element Breakdown Table
| Element | Count | Atomic mass | Calculation | Contribution |
|---|---|---|---|---|
| Hydrogen (H) | 2 | 1.01 | 2 x 1.01 | 2.02 g/mol |
| Oxygen (O) | 1 | 16.00 | 1 x 16.00 | 16.00 g/mol |
Final molar mass 2.020 + 16.000 | 18.02 g/mol | |||
Computing Molar Mass of Water Step by Step
Molar Mass of Water: Step-by-Step Calculation
1. Identify Element Counts
Read H2O and list how many atoms of each element are present:
- 2 atoms of Hydrogen (H)
- 1 atom of Oxygen (O)
2. Determine Atomic Masses
Look up each element mass from the periodic table:
- Hydrogen (H) ~= 1.008 g/mol
- Oxygen (O) ~= 15.999 g/mol
3. Multiply Atomic Mass by Quantity
Multiply atom count by atomic mass for each element:
- Hydrogen (H): 2 x 1.008 = 2.020 g/mol
- Oxygen (O): 1 x 15.999 = 16.000 g/mol
4. Sum Total Molar Mass
Add all contributions to get the final molar mass in g/mol.
Molar Mass = (2 x 1.008 + 1 x 15.999)
Molar Mass = 2.020 + 16.000
Molar Mass = 18.020 g/mol
Final rounded value shown on this page: 18.02 g/mol.
Visual Calculation Chart
| Element | Count | Mass | Count x mass | Contribution |
|---|---|---|---|---|
| Hydrogen (H) | 2 | 1.008 | 2 x 1.008 | = 2.020 |
| Oxygen (O) | 1 | 15.999 | 1 x 15.999 | = 16.000 |
Final molar mass 2.020 + 16.000 | = 18.020 | |||
Easy Way to Remember
Easy way to remember Molar Mass of Water
- Molar Mass of Water: count atoms, multiply masses, and add totals.
- Write each element in a table so you do not miss subscripts.
- Keep 2-3 decimals during steps, then round only at the end.
Sample Reactions
| Type | Reaction |
|---|---|
| Synthesis | ₂H₂ + O₂ → ₂H₂O |
| Combustion | CH₄ + ₂O₂ → CO₂ + ₂H₂O |
Do You Know?
– Water contains 2 element types: H, O.
– O contributes the largest share of this compound's total molar mass.
– In H₂O, H appears with the highest atom count.
– Its molar mass is 18.02 g/mol, which is used directly in gram-to-mole conversions.
– A common reaction for Water is synthesis (₂H₂ + O₂ → ₂H₂O).
Why This Compound Matters
Water is relevant in gas-law topics and atmosphere-focused chemistry examples.
Its molar mass is used in mole-volume and pressure-based conversion exercises.
Similar calculations can be compared with Carbon Dioxide (CO2) and Carbon Monoxide (CO).
Where This Is Used
- Competitive exams and school chemistry tests.
- Lab work when preparing measured solutions.
- Real-world manufacturing and quality checks.
Common Mistakes When Calculating This
- Skipping subscripts in H₂O and miscounting atoms.
- Rounding atomic masses too early before finishing all multiplication steps.
- Mixing up O element contribution with total molar mass.
- Reporting a value without units; final answer should be in g/mol for Water.
Quick Revision
Formula: H2O
Molar Mass: 18.02 g/mol
Key takeaway: count atoms accurately, multiply by atomic masses, and sum only at the end.
Formula Explanation
H2O contains Hydrogen (H) (2), Oxygen (O) (1). Add each element contribution to get total molar mass.
Keep molar mass page open while practicing so your totals match the same method shown here.
FAQ
Conclusion
Molar Mass of Water and Molar Mass of H₂O are now easy to revise with this structured page. You can use this method in exams, lab reports, and daily chemistry practice.