CHAPTER 9 STOICHIOMETRY IS THE BRANCH OF CHEMISTRY

CHAPTER 9 STOICHIOMETRY IS THE BRANCH OF CHEMISTRY THAT DEALS WITH: A) MASS RELATIONSHIPS OF ELEMENTS IN COMPOUNDS B) MASS RELATIONSHIPS BETWEEN REACTANTS AND PRODUCTS IN CHEMICAL REACTIONS. 1) COMPOSITION STOICHIOMETRY- DEALS WITH MASS RELATIONSHIP OF ELEMENTS IN COMPOUNDS. (Uses subscripts & Oxidation #’s) (LAW OF DEFINITE COMPOSITION & MULTIPLE PROPORTIONS) (Chap 3) 2) REACTION STOICHIOMETRY- DEALS WITH MASS RELATIONSHIPS AMONG REACTANTS AND PRODUCTS IN A CHEMICAL REACTION (BALANCED EQUATIONS & CONSERVATION OF MASS)

4 TYPES OF REACTION-STOICHIOMETRY PROBLEMS n 1) MOLE - MOLE, MOLES OF A -> MOLES OF B n n 2) 2 H 2 + O 2 2 H 2 O 2 mols + 1 mol 2 mols 6 mols +__mols ____mols MOLE - MASS, MOLES OF A -> MOLES OF B -> MASS OF B 2 H 2 + O 2 2 H 2 O n 2 mols + 1 mol 2 mols n 6 mols + 3 mols __6__mols n Mass of O 2 ____and mass of water____ Mols of O 2 x 32 g = mass of O 2 96 g) 1 MOL Mols of water x 18 g = mass of water (108 g) 1 MOL n

n n 3) MASS-MOLE, MASS OF A -> MOLS OF B n 2 H 2 + O 2 2 H 2 O n 2 mols + 1 mol 2 mols 28 g OF Hydrogen produces _______mols of water 28 g x 1 mol x 2 mol H 20 = mols of water 2 g 2 mols H 2 n n n 4) MASS-MASS, MASS A -> MOLES B -> MASS OF B 28 g of Hydrogen produces _______grams of water 28 g x 1 mol x 2 mol H 20 = mols of water x 18 g 2 g 2 mols H 2 1 mol water

CONVERSION FACTORS n MOLAR MASS AND MOLE RATIO n MOLE RATIO - CONVERSION FACTOR THAT RELATES # OF MOLES OF ANY 2 SUBSTANCES IN A REACTION *COEFFICIENTS n n Molar Mass – Mass of a mole, - Formula mass in grams

Solving Problems n TO SOLVE REACTION STOICHIOMETRY PROBLEMS: 1. BALANCE EQUATION 2. DETERMINE WHAT IS GIVEN AND WHAT IS REQUIRED. (Read Problem) (GIVEN MOLES OR MASS - REQUIRED MOLES OR MASS) n n IF GIVEN MASS, # OF MOLES OF GIVEN MUST BE CALCULATED BY THE EQUATION: MASS # OF MOLS = MOLAR MASS 3. FROM EQUATION CALCULATE MOLE RATIOS 4. USE MOLE RATIOS TO FIND THE # OF MOLS REQUIRED. (Use Coefficients) n 5. IF MASS OF REQUIRED CALCULATE USING THE SAME EQUATION MASS # OF MOLS = MOLAR MASS OR MASS = # OF MOLS x MOLAR MASS

CONVERSION FACTORS n A C) MOLAR MASS AS CONVERSION FACTOR ARE: 102 g 1 MOL Al 2 O 3 27 g 1 MOL Al E) ___32 g__ n 1 MOL OF O 2 B) I MOL Al 2 O 3 102 g D) 1 MOL Al 27 g F) 1 MOL OF O 2 32 g

CONVERSION FACTORS n n n 2 Al 2 O 3 -> 4 Al + 3 O 2 A) 2 MOLES OF ALUMINUM OXIDE OR 4 MOLES OF ALUMINUM n C) 4 MOLS OF Al n 3 MOLS OF O 2 n E) 2 MOLS OF Al 203 n n OR 3 MOLS OF O 2 OR B) 4 MOLES OF Al 2 O 3 D) 3 MOLS OF O 2 4 MOLS OF Al F) 3 MOLS OF O 2 2 MOLS OF Al 2 O THEREFORE IF GIVEN 13 MOLES OF Al 2 O 3, HOW MANY MOLS OF Al WILL BE PRODUCED. 13 MOLES OF Al 2 O 3 X 4 MOLS OF Al = 26 MOLS OF Al 2 O 3

n n n THEREFORE, IF YOU WANTED THE MASS OF THE ALUMINUM PRODUCED IN THE PREVIOUS PROBLEM, YOU CALCULATE THE FOLLOWING 26 MOLS OF Al x 27 g Al = 702 g OF Al 1 MOL OF Al

9. 2 IDEAL STOICHIOMETRY CALCULATIONS ASSUME COMPLETE CONVERSION OF ALL REACTANTS INTO PRODUCTS. n 1) MOLE - MOLE CALCULATION n MOLES OF SUBSTANCE A -> MOLS OF B n MOLES OF A x MOLE RATIO B -> MOLS OF B n A 2) MOLE - MASS CALCULATION – MOLES OF A -> MOLS OF B -> MASS OF B MOLS OF A x MOLE RATIO B x MOLAR MASS OF B = MASS OF B n A

n 3) MASS - MOLE CALCULATION – MASS OF A -> MOLS OF B MASS OF A MOLAR MASS OF A n n n x MOLE RATIO OF B -> MOLS OF B A 4) MASS - MASS CALCULATION – Mass A Mols A Mols B Mass B MASS OF A X MOLE RATIO B -> MOLS B X Molar Mass B ->Mass B MOLAR MASS OF A A