quantitative information - available from the coefficients of a balanced equation  

• coefficients represent the relative number of molecules/moles of the substance
  • 2H2O same as 2 molecules of water, or 2 moles of water
• substances in a balanced equation are stoichiometrically equivalent
• use dimensional analysis to predict amount of products/reactants
  • In the chemical equation 2H2 + O2 >> H2O, how many moles of water can be created from 4 moles of hydrogen?
  • 4 mol H2 x 1 mol H2O / 2 mol H2 = 2 mol H2O
• combinations of conversion factors can be used to predict amount of products/reactants when given known masses and a balanced equation
  • How much water can be made from 23.1 grams of hydrogen?
  • 23.1 g x 1 mol H2 / 2.01588 g x 1 mol H2O / 2 mol H2 x 18.01528 g = 103 g H2O

limiting reactant - restricts how much of the excess substance can be used  

• determines how much of the product can possibly form
  • When given 23.1 grams of hydrogen and 25.4 grams of oxygen, how much water can be produced?
  • 23.1 g x 1 mol H2 / 2.01588 g x 1 mol H2O / 2 mol H2 x 18.01528 g = 103 g H2O
  • 25.4 g x 1 mol O2 / 31.9988 g x 1 mol H2O / 1 mol O2 x 18.01528 g = 14.3 g H2O
  • oxygen, the limiting reactant, would produce less water product than hydrogen
  • no more than 14.3 grams of water can be made from the reactants given
• theoretical yield - quantity of product predicted to form if all the limiting reactant is used
• percent yield - actual yield divided by theoretical yield
  • What is the percent yield if 12.5 g of water was produced from 23.1 g of hydrogen and 25.4 g of oxygen? (see above)
  • 12.5 / 14.3 = 0.874 = 87.4%