The relationship between moles and grams is based on the molar mass of a substance.
- 1 mole of any substance contains Avogadro’s number of particles (6.022 × 10²³ atoms, molecules, or ions).
- The mass of 1 mole of a substance is equal to its molar mass in grams.
Formula:
Mass (grams)=Number of moles×Molar mass (g/mol)
Examples:
- Water (H₂O)
- Molar mass = 18 g/mol
- 1 mole of H₂O = 18 g
- So, 2 moles of H₂O = 2 × 18 = 36 g
- Carbon dioxide (CO₂)
- Molar mass = 44 g/mol
- 1 mole CO₂ = 44 g
- 0.5 moles CO₂ = 0.5 × 44 = 22 g
Key idea:
- Moles tell you how many particles you have.
- Grams tell you how much mass that number of particles represents.