Chapter 8 Table of Contents Section 1 Describing Chemical Reactions Chemical Equations and Reactions Chapter 8 Table of Contents Section 1 Describing Chemical Reactions Section 2 Balancing Chemical Equations Section 3 Classifying Chemical Reactions Section 4 Writing Net Ionic Equations

Section 1 Describing Chemical Reactions Chapter 8 Bellringer For the following situations, list observations that you think indicate that a chemical reaction has taken place: a cut apple turns brown an egg changes when it cooks a log burns a car rusts

Chapter 8 Objectives (Slides 2-15) Section 1 Describing Chemical Reactions Chapter 8 Objectives (Slides 2-15) List evidence that suggests that a chemical reaction has occurred and evidence that proves that a chemical reaction has occurred. Describe a chemical reaction by using a word equation and a formula equation. Interpret notations in formula equations, such as those relating to states of matter or reaction conditions.

Chapter 8 Chemical Reaction Section 1 Describing Chemical Reactions Chapter 8 Chemical Reaction A chemical reaction is the process by which one or more substances change into one or more new substances. Reactants are the original substances in a chemical reaction. Products are the substances that are created in a chemical reaction.

Evidence of a Chemical Reaction Section 1 Describing Chemical Reactions Chapter 8 Evidence of a Chemical Reaction

Signs of a Chemical Reaction Chapter 8 Visual Concepts Signs of a Chemical Reaction

Chapter 8 Visual Concepts Precipitate

Evidence of a Chemical Reaction Section 1 Describing Chemical Reactions Chapter 8 Evidence of a Chemical Reaction solution color changes solution bubbles copper is used up

Chemical Reaction Versus Physical Change Section 1 Describing Chemical Reactions Chapter 8 Chemical Reaction Versus Physical Change chemical change – new substance forms with properties that differ from original substance density boiling point melting point physical change - changes of state evaporation condensation melting freezing

Reactions and Energy Changes Section 1 Describing Chemical Reactions Chapter 8 Reactions and Energy Changes Energy can be released in a chemical reaction. methane + oxygen  carbon dioxide + water + energy Energy is a product. Energy can be absorbed in a chemical reaction. dinitrogen tetroxide + energy  nitrogen dioxide Energy is a reactant.

Constructing a Chemical Equation Section 1 Describing Chemical Reactions Chapter 8 Constructing a Chemical Equation A chemical equation shows the chemical formulas and relative amounts of all reactants and products. A word equation contains the names of the reactants and products. Equations must be balanced.

methane + oxygen  carbon dioxide + water Section 1 Describing Chemical Reactions Chapter 8 Writing a Word Equation or Formula Equation methane + oxygen  carbon dioxide + water ?CH4 + ?O2  ?CO2 + ?H2O

Equations and Reaction Information Section 1 Describing Chemical Reactions Chapter 8 Equations and Reaction Information Physical States NaHCO3(s) + HC2H3O2(aq)  NaC2H3O2(aq) + CO2(aq) + H2O(l) solid liquid aqueous solutions Reaction Conditions 350°C, 25 000 kPa N2(g) + 3H2(g) 2NH3(g) catalyst

Equations and Reaction Information Section 1 Describing Chemical Reactions Chapter 8 Equations and Reaction Information

Chapter 8 Visual Concepts Chemical Equation

sugar + flour + eggs + vanilla + salt  cake Section 2 Balancing Chemical Equations Chapter 8 Bellringer Write a word equation for baking a cake. Does the cake have the same properties as the ingredients? Answer: sugar + flour + eggs + vanilla + salt  cake The properties are different.

Chapter 8 Objectives (slides 16- 27) Section 2 Balancing Chemical Equations Chapter 8 Objectives (slides 16- 27) Relate the conservation of mass to the rearrangement of atoms in a chemical reaction. Write and interpret a balanced chemical equation for a reaction, and relate conservation of mass to the balanced equation.

Reactions Conserve Mass Section 2 Balancing Chemical Equations Chapter 8 Reactions Conserve Mass Mass cannot be created or destroyed by a chemical or physical change Equations must be balanced. ?Na + ?H2O  ?NaOH + ?H2

Chapter 8 Balancing Equations Section 2 Balancing Chemical Equations Chapter 8 Balancing Equations The number of atoms for each element must be the same on the reactants’ side and on the products’ side. A coefficient multiplies the number of atoms of each element in the formula that follows. H2O: 2 hydrogen atoms, 1 oxygen atom 2H2O: 4 hydrogen atoms, 2 oxygen atoms

Reading a Chemical Equation Chapter 8 Visual Concepts Reading a Chemical Equation

Chapter 8 Balancing Equations Sample Problem A Section 2 Balancing Chemical Equations Chapter 8 Balancing Equations Sample Problem A Balance the equation for the reaction of iron(III) oxide with hydrogen to form iron and water.

Chapter 8 Balancing Equations Sample Problem A Solution Section 2 Balancing Chemical Equations Chapter 8 Balancing Equations Sample Problem A Solution Identify reactants and products. reactants products Fe2O3 + H2  Fe + H2O Count atoms 3 2 3 Reactants Products Balanced? Unbalanced formula equation Fe2O3 + H2 Fe + H2O Iron atoms 2 1 no Oxygen atoms 3 Hydrogen atoms yes Insert coefficients.

Reactions Conserve Mass Section 2 Balancing Chemical Equations Chapter 8 Reactions Conserve Mass Balanced equations show mass conservation ?Na + ?H2O  ?NaOH + ?H2 2Na + 2H2O  2NaOH + H2 Never change subscripts to balance equations Unbalanced: H2 + O2  H2O Incorrect: H2 + O2  H2O2 H2O  H2O2 Correct: 2H2 + O2  2H2O

Reactions Conserve Mass Section 2 Balancing Chemical Equations Chapter 8 Reactions Conserve Mass

Polyatomic Ions can be balanced as a group Section 2 Balancing Chemical Equations Chapter 8 Polyatomic Ions can be balanced as a group

Chapter 8 Balancing Equations Section 2 Balancing Chemical Equations Chapter 8 Balancing Equations Sample Problem C Aluminum reacts with arsenic acid, HAsO3, to form H2 and aluminum arsenate. Write a balanced equation for this reaction.

Chapter 8 Balancing Equations reactants products 2 6 3 2 Section 2 Balancing Chemical Equations Chapter 8 Balancing Equations Sample Problem C Solution 1. Identify reactants and products. reactants products Al + HAsO3  H2 + Al(AsO3)3 2. Count Atoms 2 6 3 2 Reactants Products Balanced? Unbalanced formula equation Al + HAsO3 H2 + Al(AsO3)3 Iron atoms 1 yes Oxygen atoms 2 no Hydrogen atoms 3 3. Insert coefficients

Chapter 8 Bellringer Describe the following terms. synthesis Section 3 Classifying Chemical Reactions Chapter 8 Bellringer Describe the following terms. synthesis decomposition displacement

Chapter 8 Objectives (slides 28-49) Section 3 Classifying Chemical Reactions Chapter 8 Objectives (slides 28-49) Identify combustion reactions, and write chemical equations that predict the products. Identify synthesis reactions, and write chemical equations that predict the products. Identify decomposition reactions, and write chemical equations that predict the products.

Chapter 8 Objectives, continued Section 3 Classifying Chemical Reactions Chapter 8 Objectives, continued Identify displacement reactions, and use the activity series to write chemical equations that predict the products. Identify double-displacement reactions, and write chemical equations that predict the products.

Chapter 8 Combustion Reactions Section 3 Classifying Chemical Reactions Chapter 8 Combustion Reactions A combustion reaction is a reaction of a carbon-based compound with oxygen. Combustion of propane: C3H8 + 5O2  3CO2 + 4H2O Combustion of ethanol: CH3CH2OH + 3O2  2CO2 + 3H2O

Chapter 8 Visual Concepts Combustion Reaction

CaO(s) + H2O(l)  Ca(OH)2(s) Section 3 Classifying Chemical Reactions Chapter 8 Synthesis Reactions In a synthesis reaction a single compound forms from two or more reactants. Two elements form a binary compound C + O2  CO2 2C + O2 2CO Two compounds form a ternary compound CaO(s) + H2O(l)  Ca(OH)2(s) CO2(g) + H2O(l)  H2CO3(aq)

Chapter 8 Visual Concepts Synthesis Reactions

Decomposition Reactions Section 3 Classifying Chemical Reactions Chapter 8 Decomposition Reactions In a decomposition reaction a single compound breaks down, often with the input of energy, into two or more elements or simpler compounds. Decomposition of water electricity 2H2O(l) O2(g) + 2H2(g) A metal carbonate decomposes to form a metal oxide and carbon dioxide. heat CaCO3(s) CaO(s) + CO2(g)

Decomposition Reaction Chapter 8 Visual Concepts Decomposition Reaction

Chapter 8 Visual Concepts Electrolysis

Decomposition Reactions, continued Section 3 Classifying Chemical Reactions Chapter 8 Decomposition Reactions, continued Sample Problem D Predicting Products Predict the product(s) and write a balanced equation for the reaction of potassium with chlorine.

Decomposition Reactions, continued Section 3 Classifying Chemical Reactions Chapter 8 Decomposition Reactions, continued Sample Problem D Solution Reaction is most likely a synthesis reaction, so the product will be binary Potassium will lose one electron to become a 1+ ion. Chlorine will gain one electron to become a 1– ion. K + Cl2  KCl Balance the equation. 2K + Cl2  2KCl

Displacement Reactions Section 3 Classifying Chemical Reactions Chapter 8 Displacement Reactions In a displacement reaction a single element reacts with a compound and displaces another element from the compound. 2Al(s) + 3CuCl2(aq)  2AlCl3(aq) + 3Cu(s) Aluminum displaces copper.

Single Displacement Reaction Chapter 8 Visual Concepts Single Displacement Reaction

Displacement Reactions, continued Section 3 Classifying Chemical Reactions Chapter 8 Displacement Reactions, continued The activity series ranks the reactivity of elements

Chapter 8 Visual Concepts Activity Series

Displacement Reactions, continued Section 3 Classifying Chemical Reactions Chapter 8 Displacement Reactions, continued Sample Problem E Determining Products by Using the Activity Series Magnesium is added to a solution of lead(II) nitrate. Will a reaction happen? If so, write the equation and balance it.

Displacement Reactions, continued Section 3 Classifying Chemical Reactions Chapter 8 Displacement Reactions, continued Sample Problem E Solution Identify the reactants. Magnesium will attempt to displace lead from lead(II) nitrate. Check the activity series. Magnesium is more active than lead and displaces it. Write the balanced equation. Mg + Pb(NO3)2  Pb + Mg(NO3)2

HCl(aq) + NaOH(aq)  HOH(l) + NaCl(aq) Section 3 Classifying Chemical Reactions Chapter 8 Double-Displacement Reactions In a double-displacement reaction two compounds in aqueous solution appear to exchange ions and form two new compounds. One of the products must be a solid precipitate, a gas, or a molecular compound, such as water. HCl(aq) + NaOH(aq)  HOH(l) + NaCl(aq)

Double-Displacement Reaction Chapter 8 Visual Concepts Double-Displacement Reaction

Chapter 8 Identifying Reactions and Predicting Products

Understanding Concepts Chapter 8 Standardized Test Preparation Understanding Concepts 2. Which of these sentences correctly states the law of conservation of mass? F. In a chemical reaction, the mass of the products cannot exceed the mass of the reactants. G. In a chemical reaction, the mass of the products is always equal to the mass of the reactants. H. In a chemical reaction, the mass of the products is always less than the mass of the reactants. I. In a chemical reaction, the mass of the products is always greater than the mass of the reactants.

Section 4 Writing Net Ionic Equations Chapter 8 Bellringer Write a definition for the word spectator in terms of the part spectators play in a sporting event.

Objectives (skip Section 8.4) Section 4 Writing Net Ionic Equations Chapter 8 Objectives (skip Section 8.4) Write total ionic equations for reactions in aqueous solutions. Identify spectator ions and write net ionic equations for reactions in aqueous solutions.

Ionic Equations, continued Section 4 Writing Net Ionic Equations Chapter 8 Ionic Equations, continued Ionic compounds dissolve in water KI(aq) = K+(aq) + I–(aq) Pb(NO3)2(aq) = Pb2+(aq) + (aq) Reaction between KI and Pb(NO3)2 2KI(aq) + Pb(NO3)2(aq)  PbI2(s) + 2KNO3(aq) Total Ionic Equation 2K+(aq) + 2I–(aq) + Pb2+(aq) + (aq)  PbI2(s) + 2K+(aq) + (aq)

2I–(aq) + Pb2+(aq)  PbI2(s) Section 4 Writing Net Ionic Equations Chapter 8 Ionic Equations, continued Spectator ions remain unchanged in the solution as aqueous ions. They do not react. 2K+(aq) + 2I–(aq) + Pb2+(aq) + (aq)  PbI2(s) + 2K+(aq) + (aq) The net ionic equation is the chemical equation that shows only the net change. 2I–(aq) + Pb2+(aq)  PbI2(s)

Chapter 8 Visual Concepts Net Ionic Equation

Zn(s) + Cu2+(aq)  Cu(s) + Zn2+(aq) Section 4 Writing Net Ionic Equations Chapter 8 Ionic Equations, continued Net Ionic equations can be used for displacement reactions. Zn(s) + Cu2+(aq) + (aq)  Cu(s) + Zn2+(aq) + (aq) net ionic equation Zn(s) + Cu2+(aq)  Cu(s) + Zn2+(aq)

Ionic Equations, continued Section 4 Writing Net Ionic Equations Chapter 8 Ionic Equations, continued Check atoms and charge to balance net ionic equations. (aq) + Ba2+(aq)  BaSO4(s) Charge: (2–) + (2+) = 0 0 Zn(s) + Cu2+(aq)  Cu(s) + Zn2+(aq) Charge: 2+ 2+

Chapter 8 Writing a Net Ionic Equation