Ch 9 Stoichiometry How does this apply to everyday life? Following recipe for cooking/ baking Following directions in building/construction Knowing how much of ingredients needed Using Balanced Chem Eqns Knowing how much reagent(s) needed to make product or how much product formed in reaction Stoichiometry: “element” and “to measure” = calculation of amounts of substances involved in chem rxn

9.1 Intro 4 Types of Problems Mole Ratios Remember Molar Mass mol given moles of unknown moles given mass of unknown mass given moles of unknown mass given mass of unknown Mole Ratios Written as conversion factors Remember Molar Mass Mass (g) of 1 mol of substance

9.2 Ideal Stoichiometric Calculations Don’t Forget Mass Conservation! (Mass and atoms conserved; reactants = products) Given quantity x conversion factor = unknown quantity Type 1: mole-to-mole conversion Type 2: mole-to-gram conversion Type 3: gram-to-mole conversion Type 4: mass-to-mass conversion

Arithmetic of Equations Interpreting Chem Eqns Quantities of atoms: # and type of atoms in reactant(s) and product(s) Quantities of molecules: # and type of molecules in reactant(s) and product(s) Quantities of moles: coefficients of balanced ch rxn is # moles of reactants/ products! Mass: follows law of conservation of mass; use mole relationships Volume: remember 1 mole of gas at STP has volume of 22.4L; coefficients to know relative volumes

Chem Calculations Moles ratios used? Steps in Stoichiometric problems Mole ratios are the coefficients in a balanced chemical equation! Relates reactants to products Steps in Stoichiometric problems Get moles: Convert given quantity to moles Mole Ratio: Use mole ratio from equations to find moles of wanted component Get Right Units: Convert moles of wanted to desired unit

9.3Limiting Reagent and Percent Yield Limiting Reagents: insufficient quantity, run out reaction is over/ limit product made Excess Reagents: not completely used up/ have extra when reaction is over

Yield Theoretical yield: max amount of product that could be formed from all reactants Actual Yield: amount actually formed in exp. Percent yield = actual yield/ theoretical yield x100% Measures efficiency of exp; remember % error