STUDENT SPACE · TOPIC 2
Reacting moles and limiting reactants
Use mole ratios to calculate product mass, limiting reactants and yield.
The essentials
- 2Mg + O₂ → 2MgO gives a mole ratio of 2:1:2.
- Convert mass to moles before applying the coefficient ratio.
- 4.8 g Mg in excess oxygen: n(Mg) = 4.8/24 = 0.20 mol.
- n(MgO) = 0.20 mol; mass = 0.20 × 40 = 8.0 g.
Key vocabulary
| English | Chinese |
|---|---|
| mole ratio | 物质的量之比 |
| limiting reactant | 限制反应物 |
| percentage yield | 产率 |
Quick practice
Why must a theoretical yield use the limiting reactant?
Need a hint?
Use the relationships above and check particle ratios and units.
Check your reasoning after trying
That reactant runs out first and sets the maximum amount of product.
Use Lesson 2 in your worksheet for written practice. Your teacher will discuss those answers in class.