Balancing Chemical Equations and Types of Chemical Reactions Unit 4 1

What is a chemical equation? Parts of an equation: 2Ag + H2S Ag2S + H2 Reaction symbol

Reactants and Products 3

Subscripts and Coefficients ‏ Coefficient - 4

2H2 + O2 → 2H2O 6

Law of Conservation of Mass In a chem. rxn, matter is If an equation obeys the Law of Conservation, 7

Choosing the order of balancing Start Save for later Pb + PbO2 + H+ → Pb2+ + H2O Start Elements that appear only 1 time per side Start Save for later To balance this equation, use the order: O, H, Pb

Rules of Balancing 1. 9

Rules of Balancing A few extra tips: 10

. CH4 + O2 → CO2 + H2O 1 carbon atom 4 hydrogen atoms 2 oxygen atoms 11

CH4 + O2 → CO2 + H2O 1 carbon atom 4 hydrogen atoms 4 oxygen atoms 12

DO NOW: What are the reactants in this chemical equation? C O2 → CO2 1 Carbon atom 1 oxygen molecule → 1 carbon dioxide molecule What are the reactants in this chemical equation? What are the products in this chemical equation? Are there the same number of atoms on both sides of the equation? Where any atoms destroyed or created? Was the Law of Conservation of Matter maintained?

Balancing Equations _ _ 2 1 2 3 N2 + H2 → NH3 N H Balance the following equation by adjusting coefficients. N2 + H2 → NH3 _ _ reactants products N 2 1 2 3 H 15

Balancing Equations 3 2 2 2 1 6 2 6 3 N2 + H2 → NH3 N H Balance the following equation by adjusting coefficients. N2 + H2 → NH3 3 2 reactants products N 2 2 1 6 2 6 3 H 16

Balancing Equations _ _ 1 1 1 1 3 2 KClO3 → KCl + O2 K Cl O Balance the following equation by adjusting coefficients. _ KClO3 → KCl + O2 _ reactants products K 1 1 Cl 1 1 3 2 O 17

Balancing Equations 3 2 2 2 1 1 2 2 1 2 1 6 3 2 6 KClO3 → KCl + O2 K Balance the following equation by adjusting coefficients. 3 2 KClO3 → KCl + O2 2 reactants products K 2 1 1 2 Cl 2 1 2 1 6 3 2 6 O 18

DO NOW: Is this equation balanced? 3 H2SO4 + 2 B(OH)3 → B2 (SO4) 3 + 6 H2O If not, balance it!

Balancing Equations Balance the following equation: __C2H6 + __ O2 → __ CO2 + __ H2O 20

__Fe + __ O2 → __ Fe2O3 Balancing Equations Balance the following equation: __Fe + __ O2 → __ Fe2O3 21

Balancing Equations Balance the following equation: __ HCl + __ Ca(OH)2 → __ CaCl2 + __ H2O __ H2 + __ O2 → __ H2O ____ P4 + ____ O2 → ____ P2O3 22

DO NOW Balance the following equation: ___ Ga + ___ H2SO4 ___ Ga2(SO4)3 + ___ H2 23

5 Types of Chemical Reactions

Combination A+ B → AB

Decomposition AB → A + B

Single Displacement

Double Displacement AB + CD → CB + AD

Combustion

Activity Series

Examples Mg + Cu(NO3)2 → Fe + NA2SO4 → Zn + MnCl2 → 2Al + 3SnSO4 →

Examples 2Al + 3SnSO4 → Mg + Cu(NO3)2 → Mg(No3)2 + Cu Fe + Na2SO4 → no rxn Zn + MnCl2 → no rxn 2Al + 3SnSO4 → Al2(SO4)3 + 3 SN

DO NOW: Will a reaction occur in the following single displacement reactions? If yes, write the products… Fe + Al2O3 → Ca + 2HCl →

The Mole

The Mole … what is it? Abbreviation for the mole: mol A mole is defined as the number of atoms in exactly 12 grams of carbon- 12 The number is called Avogadro’s Number One mole of carbon atoms has a mass of 12 grams Abbreviation for the mole: mol

A Mole of Particles Contains 6.02 x 1023 particles 1 mole C = 6.02 x 1023 C atoms 1 mole H2O = 6.02 x 1023 H2O molecules 1 mole NaCl = 6.02 x 1023 NaCl molecules

What does a mole count in? Avogadro’s Number: 6.022142 x 1023 “things” = 1 mole 6.02 × 1023 = 602,000,000,000,000,000,000,000 ! “mole” 6.02 × 1023 1 mole of doughnuts 6.02 × 1023 doughnuts 1 mole of atoms 6.02 × 1023 atoms 1 mole of molecules 6.02 × 1023 molecules This means a 12 ounce bottle of water would have 19.7 “moles” of water…a much easier-to-work-with number!

Converting to Molar Mass Molar Mass: The mass for one mole of an atom of molecule Other terms commonly used for the same meaning: Molecular Weight Molecular Mass Formula Weight Formula Mass

Unit for molar mass: g/mole or g/mol Mass of 1 Mole of Atoms The average atomic mass = grams for 1 mole Average atomic mass found on periodic table Element Mass 1 mole of carbon atoms 12.01 g 1 mole of oxygen atoms 16.00 g 1 mole of hydrogen atoms 1.01 g Unit for molar mass: g/mole or g/mol

Calculating a Molecule’s Mass To find the molar mass of a molecule: 1 Count the number of each type of atom 2 Find the molar mass of each atom on the periodic table 3 Multiple the # of atoms × molar mass for each atom 4 Find the sum of all the masses

Example Problem - Molar Mass Find the molar mass for CaBr2

Example Problem - Molar Mass Count the number of each type of atom 1 Example: Find the molar mass for CaBr2 Ca 1 Br 2

Example Problem - Molar Mass 2 Find the molar mass of each atom on the periodic table Example: Find the molar mass for CaBr2 Ca 1 40.08 g/mole Br 2 79.91 g/mole

Example Problem - Molar Mass Multiply the # of atoms x molar mass for each atom 3 Example: Find the molar mass for CaBr2 Ca 1 x 40.08 = 40.08 g/mole Br 2 x 79.91 = 159.82 g/mole

Example Problem - Molar Mass Find the sum of all the masses 4 Example: Find the molar mass for CaBr2 Ca 1 x 40.08 = 40.08 g/mol Br 2 x 79.91 = 159.82 g/mol 199.90 g/mol 1 mole of CaBr2 molecules would have a mass of 199.90 g

Example of Molar Mass and Parenthesis Be sure to distribute the subscript outside the parenthesis to each element inside the parenthesis. Example: Find the molar mass for Sr(NO3)2

Example of Molar Mass and Parenthesis Be sure to distribute the subscript outside the parenthesis to each element inside the parenthesis. Example: Find the molar mass for Sr(NO3)2 Sr 1 × 87.62 g/mole = 87.62 g/mole N 2 × 14.01 g/mole = 28.02 g/mole O 6 × 16.00 g/mole = + 96.00 g/mole 211.64 g/mole 1 mole of Sr(NO3)2 molecules would have a mass of 211.64 g

Example of Molar Mass and Parenthesis Be sure to distribute the subscript outside the parenthesis to each element inside the parenthesis. Example: Find the molar mass for Al(OH)3

Example of Molar Mass and Parenthesis Be sure to distribute the subscript outside the parenthesis to each element inside the parenthesis. Example: Find the molar mass for Al(OH)3 Al 1 × 26.98 g/mole = 26.98 g/mole O 2 × 16.00 g/mole = 32.00 g/mole H 2 × 1.01 g/mole = + 2.02 g/mole 61.00 g/mole 1 mole of Al(OH)3 molecules would have a mass of 61.00 g

Percent Composition %

The percent by mass of each element present in a compound. Percent Composition The percent by mass of each element present in a compound. Example: H2O → 1 mole = 18.01 grams of H2O 2 moles of H: 2 x 1.008 = 2.016 grams 1 mole of O: 1 x 16 = 16 grams % of H → 2.018 x 100% = 11.19% % of O → 16 x 100% = 88.81% 18.016 18.016

Example: KMnO4 Find the mass of each element: K → Mn → O (4) →

Example: C6H12O6 First, find the masses of each element: C (6) → H (12) → O (6) →

Using Molar Mass in Conversions

Example: Moles to grams How many grams are in 1.25 moles of water? 1 H O 2 1 1.01 g/mole 16.00 g/mole × = 2.02 g/mole + 18.02 g/mole 1 mole H2O molecules = 18.02 g

Example: Moles to grams How many grams are in 1.25 moles of water? 2 1 mole H2O molecules = 18.02 g 1.25 mol H2O 18.02 g H2O = _______ g H2O 22.53 1 mol H2O

Example: Grams to moles How many moles are in 25.5 grams of NaCl? 1 Na Cl 1 22.99 g/mole 35.45 g/mole × = + 58.44 g/mole 1 mole NaCl molecules = 58.44 g

Example: Moles to grams How many moles are in 25.5 grams of NaCl? 1 mole NaCl = 58.44 g 2 25.5 g NaCl 1 mole NaCl = _______ mole NaCl 0.44 58.44 g NaCl

Example: Grams to Molecules How many molecules are in 25.5 grams NaCl? Think: what steps need to be taken? 1. Convert grams to moles 2. Convert moles to molecules

Example: Grams to Molecules How many molecules are in 25.5 grams NaCl? Example: Grams to Molecules 1 Na Cl 1 22.99 g/mole 35.45 g/mole × = + 58.44 g/mole 1 moles NaCl molecules = 58.44 g 1 mol = 6.02×1023 molecules

Example: Grams to Molecules How many molecules are in 25.5 grams NaCl? Example: Grams to Molecules 2 1 moles NaCl molecules = 58.44 g 1 mol = 6.02×1023 molecules 25.5 g NaCl 1 mol NaCl 6.02×1023 molecules NaCl 58.44 g NaCl 1 mol NaCl = _________ molecules NaCl 2.63 × 1023

Example: Molecules to grams How many grams is a sample of 2.75 x 1024 molecules of SrCl2? Think: what steps need to be taken? 1. Convert molecules to moles 2. Convert moles to grams

Example: Molecules to grams How many grams is a sample of 2.75 x 1024 molecules of SrCl2? Example: Molecules to grams 1 Sr Cl 1 2 87.62 g/mole 35.45 g/mole × = 70.90 g/mole + 158.52 g/mole 1 moles SrCl2 molecules = 158.52 g 1 mol = 6.02×1023 molecules

Example: Molecules to Grams How many grams is a sample of 2.75 x 1024 molecules of SrCl2? Example: Molecules to Grams 2 1 moles SrCl2 molecules = 158.52 g 2.75 × 1024 molecules SrCl2 1 mol SrCl2 158.52 g SrCl2 6.02 × 1023 molecules SrCl2 1 mol SrCl2 = _________ g SrCl2 7.24