Molar Mass Calculator
Write according to IUPAC convention (e.g. H2O, not OH2)
What is Molar Mass?
Molar mass is the mass of exactly 1 mole of a substance. It is measured in g/mol.
1 mole contains 6.022 × 10²³ particles (Avogadro's constant).
Calculation:
Molar mass is calculated from the atomic masses of all atoms in the chemical formula:
M = Σ(n × A)
n = number of atoms, A = atomic mass
n = number of atoms, A = atomic mass
Examples:
- H₂O: 18.016 g/mol
- CO₂: 44.01 g/mol
- NaCl: 58.44 g/mol
- C₆H₁₂O₆: 180.16 g/mol
Formulas
Molar Mass from Formula:
M = Σ(n_i × A_i) [g/mol]
n_i = number of atoms, A_i = atomic mass
M = Σ(n_i × A_i) [g/mol]
n_i = number of atoms, A_i = atomic mass
Calculate Moles:
n = m / M
m = mass, M = molar mass
n = m / M
m = mass, M = molar mass
Molar Mass from Total Mass:
M = m / n [g/mol]
m = total mass, n = number of moles
M = m / n [g/mol]
m = total mass, n = number of moles
Calculate Mass:
m = n × M
n = moles, M = molar mass
m = n × M
n = moles, M = molar mass
Examples
Water (H₂O)
• H: 2 × 1.008 = 2.016 g/mol
• O: 1 × 16.00 = 16.00 g/mol
• M = 18.016 g/mol
• H: 2 × 1.008 = 2.016 g/mol
• O: 1 × 16.00 = 16.00 g/mol
• M = 18.016 g/mol
Carbon Dioxide (CO₂)
• C: 1 × 12.01 = 12.01 g/mol
• O: 2 × 16.00 = 32.00 g/mol
• M = 44.01 g/mol
• C: 1 × 12.01 = 12.01 g/mol
• O: 2 × 16.00 = 32.00 g/mol
• M = 44.01 g/mol
Calcium Hydroxide (Ca(OH)₂)
• Ca: 1 × 40.08 = 40.08 g/mol
• O: 2 × 16.00 = 32.00 g/mol
• H: 2 × 1.008 = 2.016 g/mol
• M = 74.10 g/mol
• Ca: 1 × 40.08 = 40.08 g/mol
• O: 2 × 16.00 = 32.00 g/mol
• H: 2 × 1.008 = 2.016 g/mol
• M = 74.10 g/mol
Glucose (C₆H₁₂O₆)
• M = 180.16 g/mol
• M = 180.16 g/mol
Technical Background
Avogadro's Constant
Avogadro's constant (N_A = 6.022 × 10²³ mol⁻¹) is the number of particles per mole. It connects the atomic scale to the macroscopic scale.
Stoichiometric Relationships
| Calculate moles: | n = m / M (moles = mass / molar mass) |
| Calculate mass: | m = n × M (mass = moles × molar mass) |
Standard Atomic Masses (g/mol)
| Element | Symbol | Atomic Mass |
|---|---|---|
| Hydrogen | H | 1.008 g/mol |
| Carbon | C | 12.01 g/mol |
| Nitrogen | N | 14.01 g/mol |
| Oxygen | O | 16.00 g/mol |
| Sodium | Na | 23.00 g/mol |
| Magnesium | Mg | 24.31 g/mol |
| Sulfur | S | 32.07 g/mol |
| Chlorine | Cl | 35.45 g/mol |
| Calcium | Ca | 40.08 g/mol |
| Iron | Fe | 55.85 g/mol |
Applications
- Stoichiometric Calculations in chemical reactions
- Concentration Calculation (Molarity M = mol/L)
- Laboratory Work – weighing and dissolving substances
- Titration and analytical chemistry
|
|
|
|