LET’S TRY ONE
For 2H2 + O2 → 2H2O, what amount of O2 is required for 4 mol H2, assuming the reaction follows this ratio?
2 mol
The H2:O2 ratio is 2:1, so 4 mol H2 requires 2 mol O2.
Learning steps & teaching tips
Use a supplied balanced equation or molar mass to calculate amounts with stated units.
- Check which equation coefficients relate the substances.
- Scale the stated mole ratio.
- Keep moles and grams distinct when using a molar mass.
Try it together
Represent a balanced reaction using counters labelled as moles. Double and halve the reaction amounts, then attach supplied mass-per-mole cards.
Read coefficients as mole ratios, and use only the supplied molar masses for mass conversions.