StudyBrixFree worksheets, study guides and courses

Chemistry · Grades 10–12

Yield, purity and limiting amounts

Do not confuse an impure recovered mass with a chemical yield.

Make a worksheet

Learn the idea

Yield

Percent yield = actual amount / theoretical amount × 100 for the same product quantity.

Limiting

The limiting reactant is exhausted first under the stated stoichiometric model.

Purity

Mass purity is the mass of desired substance divided by sample mass.

Caution

A reported yield over 100% can indicate impurities, solvent or measurement/model errors.

Worked examples

Theoretical product mass is 20 g and actual dry pure mass is 15 g. Find percent yield.

15/20 × 100 = 75%.

75 %

A 40 g sample contains 30 g desired substance. Find mass purity.

30/40 × 100 = 75%.

75 %

Check your understanding

  1. What identifies the limiting reactant?

    1. Always the smallest mass.
    2. Always the most expensive substance.
    3. The reactant that limits product according to the balanced mole ratio.

  2. For A + 2B → C, 3 mol A and 4 mol B are available. Find the maximum moles of C.

  3. Why can a wet recovered solid produce an apparent yield above 100%?

Answers and marking notes

Answers and marking notes
  1. The reactant that limits product according to the balanced mole ratio.

    Mass alone does not determine the limiting amount.

  2. 2 mol

    B allows 4/2 = 2 mol C; A would allow 3, so B limits.

  3. Retained solvent adds mass not belonging to the intended dry product.

    Other sources include impurities and incorrect assumptions.

Further reading and review references

These are reference links, not copied exercises, institutional endorsement or proof of independent review.

Independent educational review required. Grade bands are approximate; these are not officially aligned curricula.