Ch. 9 Stoichiometry Stoichiometry is a branch of chemistry that deals with the mass relationships of elements in compounds and the mass relationships between reactants and products in chemical reactions. 2 Types of Stoichiometry 1. Composition Stoichiometry – is the mass relationships of elements in chemical compounds. Ex. Molar mass of Li is 6.941 grams

2. Reaction Stoichiometry – is the mass relationship among reactants and products of a chemical reaction. Ex. NaCl + H2O  HCl + NaOH 58.44g 18.02g 36.46g 40.00g 4 Reaction – Stoichiometry Problems 1. Mole to Mole 2. Mass to Mass 3. Mole to Mass 4. Mass to Mole

EXAMPLES ??? Sample Problems 9.1 – 9.5 Limiting Reactant is the reactant that limits the amount of the other reactants that can combine, and the amount of products formed in a chemical reaction. Excess Reactant is the substance that is not used up completely in a reaction. Ex. If a bus holds 50 people and 60 are waiting to ride the bus, 10 will be left in excess. Sample problems 9.6 – 9.7

Percent Yield is the ratio of the actual yield to theoretical yield times 100%. (Actual yield / Theoretical yield) X 100% Theoretical yield is the maximum amount of product that can be produced from a given amount of reactant. Actual yield is the measured amount of a product obtained from the product of a reaction. Sample Problem 9.8