Safety boundary
Use paper models, supplied data, and approved simulations only. No unsupervised reactive mixtures are required.
Explicit chemistry instruction
Molar mass is the mass of one mole of a substance, usually expressed in g/mol.
For a compound, add atomic masses according to subscripts. Parentheses and coefficients must be interpreted carefully.
Mass-to-mole conversion uses n=m/M. The molar mass belongs to the chemical formula, not to the sample size.
Vocabulary: molar mass; formula mass; grams; moles; conversion factor.
Worked example
H₂O has molar mass about 18.02 g/mol. A 36.04 g sample therefore contains 2.00 mol.
Guided question
Calculate the molar mass of CO₂ and determine moles in 22.0 g.
Independent work
- Calculate molar masses for four formulas.
- Convert three masses to moles.
- Convert two mole amounts to grams.
Misconception check
Do not multiply molar mass by a coefficient unless the question is about that many moles of substance.
Formative check
What determines a compound's molar mass?
Reveal response
Its chemical formula and constituent atomic masses.
Mentor evidence conference
Ask Archaemenes to audit units, conversion factors, equation coefficients, and model assumptions.
Teacher guidance
Foundation: Use formula/subscript organizers.
Core: Complete mass↔mole conversions.
Extended: Audit unit cancellation and significant figures.