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# How do I compute mass of product (O2) from mass of reactant (KClO3)?

50.0 g of potassium chlorate is decomposed by heating. What is the mass of O2 prepared?

1. Calculate moles of KClO3 decomposed. To convert grams to moles, use the molecular weight of the compound:
 50.0 g KClO3 × 1 mol KClO3122.6 g KClO3 = 0.408 mol KClO3
2. Calculate moles of O2 prepared. To convert moles of one substance to moles of another, you need a balanced chemical equation that relates them. In this case, it's
2 KClO3 2 KCl + 3 O2
The coefficients in the equation give the mole-to-mole conversion factor:
 0.408 mol KClO3 × 3 mol O21 mol KClO3 = 0.610 mol O2
3. Calculate the mass of O2 prepared. Again, to convert moles to grams, use the molecular weight of the compound:
 = 0.610 mol O2 32.0 g O21 mol O2 = 19.6 g O2

Author: Fred Senese senese@antoine.frostburg.edu

General Chemistry Online! How do I compute mass of product (O_2_) from mass of reactant (KClO_3_)?