Stoichiometry  the calculations of quantities in chemical reactions  “stoichio” = elements  “metry” = to measure

N 2 + 3H 2 2NH 3  Information that can be derived from a chemical equation: 1.Particles – ratio of particles always remains the same 2.Moles – coefficients of a balanced equation indicate the number of moles of reactants and products

N 2 + 3H 2 2NH 3 3.Mass – a balanced equation must obey the law of conservation of mass – the mass of the reactants must equal the mass of the products (even though the number of moles may be different) 4.Volume – a balanced equation will indicate the volume of gases (1 mole = 22.4 L)

N 2 + 3H 2 2NH 3  Mole ratios – used to calculate the number of moles of a product from a given number of moles of a reactant (or visa-versa)  Ratios: 1 mol N 2 3 mol H 2 2 mol NH 3 1 mol N 2 3 mol H 2 2 mol NH 3

How many moles of ammonia (NH 3 ) are produced when 0.60 mol of nitrogen reacts with hydrogen? N 2 + 3H 2 2NH mol N 2 2 mol NH 3 1 mol N 2 = 1.2 mol NH 3

Try These! 1.How many moles of aluminum are needed to form 3.7 mol Al 2 O 3 ? 2.How many moles of oxygen are required to react completely with 14.8 mol Al? 3.How many moles of Al 2 O 3 are formed when 0.78 mol oxygen reacts with aluminum? 4Al + 3O 2 2Al 2 O 3

Here’s the good stuff - Representative particles R Mass R Volume of gas R 1 mol R 6.02 X mol R mass R 1 mol R 22.4 L R Representative particles P Mass P Volume of gas P 6.02 X mol P mass P 1 mol P 22.4 L P 1 mol P # mol P # mol R

CaC 2 + 2H 2 O C 2 H 2 + Ca(OH) 2 How many grams of C 2 H 2 are produced by adding water to 5.0 g CaC 2 ? ? g C 2 H 2 = 5.0 g CaC g CaC 2 64 g CaC 2 1 mol CaC 2 1 mol C 2 H 2 26 g C 2 H 2 = 2.03 g C 2 H 2

CaC 2 + 2H 2 O C 2 H 2 + Ca(OH) 2 How many molecules of calcium hydroxide are produced if 48.2 grams of water are combined with CaC 2 ? ? molecules Ca(OH) 2 = 48.2 g H 2 O 48.2 g H 2 O 18 g H 2 O 1 mol H 2 O 2 mol H 2 O 1 mol Ca(OH) X mc Ca(OH) 2 = 8.06 X mc Ca(OH) 2