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Chemistry · Grades 9–12

Mass of a pure component

Convert purity percent to a fraction before multiplying the total sample mass.

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Rule and assumptions

Convert purity percent to a fraction before multiplying the total sample mass.

component mass = sample mass × purity/100

Worked examples

A 33 g sample is 24% desired substance by mass. Find the desired substance mass. Round to 3 decimal places if needed. Answer in g.

component mass = sample mass × purity/100 33 × 24/100 = 7.92

7.92 g

A 158 g sample is 85% desired substance by mass. Find the desired substance mass. Round to 3 decimal places if needed. Answer in g.

component mass = sample mass × purity/100 158 × 85/100 = 134.3

134.3 g

Try two questions

  1. A 32 g sample is 85% desired substance by mass. Find the desired substance mass. Round to 3 decimal places if needed. Answer in g.

  2. A 19 g sample is 65% desired substance by mass. Find the desired substance mass. Round to 3 decimal places if needed. Answer in g.

Answers and reasoning

Answers and marking notes
  1. 27.2 g

    component mass = sample mass × purity/100 32 × 85/100 = 27.2

  2. 12.35 g

    component mass = sample mass × purity/100 19 × 65/100 = 12.35

Further reading and review references

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Learning preview · independent educational and translation review required. Suggested grades are not official curriculum alignment.