Stoichiometry CaCO3 a CaO + CO2 involves the mass relationships between reactants and products in a chemical reaction. Example CaCO3 a CaO + CO2 10 g ? g or ? g

2 H2 + O2 a 2 H2O 2 molecules 1 molecule 2 molecules 2000 molecules 2 dozen molecules 1 dozen molecules 2 dozen molecules 2 moles molecules 1 mole molecules 2 moles molecules 1 dozen = 12 1 mole = 6.02 x 1023

The coefficients represent the number of moles reacting (not the number of grams). 2 H2 + O2 a 2 H2O 2 grams ? grams 2 moles 2 moles 2 grams of H2 does not make 2 grams H2O but 2 moles of H2 does make 2 moles H2O

2 2 H2 + O2 a 2 H2O 1 Stoichiometry Problem 4 moles H2 ? moles O2 2 x ____________ = 2 moles O2 moles H2 molar ratio step

2 H2 + O2 a 2 H2O 2 2 4 ? moles H2O 4 moles H2 moles H2O 4 moles H2 x ____________ = 4 moles H2O moles H2 molar ratio step

2 H2 + O2 a 2 H2O 2 1 6 grams H2 1.5 ? moles O2 3 moles H2 6 grams H2 1 mole H2 moles O2 x ____________ x ____________ = 1.5 moles O2 2 grams H2 moles H2 molar ratio step 3 moles H2

2 H2 + O2 a 2 H2O 90 grams H2O 5 moles H2 5 moles H2O 10 grams H2 1 mole H2 2 moles H2O 18 grams H2O x x ____________ x ____________ ___________ = 2 grams H2 2 moles H2 1 mole H2O 90 grams H2O 5 moles H2

2 H2 + O2 a 2 H2O 90 grams H2O 10 grams ? grams 5 moles H2 5 moles H2O

Change moles A to moles C A + B a C Grams A Moles A Moles C Grams C Change grams to moles Change moles A to moles C Change moles to grams