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Table of Contents

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.

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Table of Contents

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

  2. Section1 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

  3. Section1 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.

  4. Section1 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.

  5. Section1 Describing Chemical Reactions Chapter 8 Evidence of a Chemical Reaction

  6. Visual Concepts Chapter 8 Signs of a Chemical Reaction

  7. Visual Concepts Chapter 8 Precipitate

  8. Section1 Describing Chemical Reactions Chapter 8 Evidence of a Chemical Reaction • solution color changes • solution bubbles • copper is used up

  9. Section1 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

  10. Section1 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.

  11. Section1 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.

  12. Section1 Describing Chemical Reactions Chapter 8 Writing a Word Equation or Formula Equation methane + oxygen  carbon dioxide + water ?CH4 + ?O2  ?CO2 + ?H2O

  13. Section1 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

  14. Section1 Describing Chemical Reactions Chapter 8 Equations and Reaction Information

  15. Visual Concepts Chapter 8 Chemical Equation

  16. Section2 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.

  17. Section2 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.

  18. Section2 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

  19. Section2 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. • Acoefficient 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

  20. Visual Concepts Chapter 8 Reading a Chemical Equation

  21. Section2 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.

  22. Section2 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 • Insert coefficients.

  23. Section2 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

  24. Section2 Balancing Chemical Equations Chapter 8 Reactions Conserve Mass

  25. Section2 Balancing Chemical Equations Chapter 8 Polyatomic Ions can be balanced as a group

  26. Section2 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.

  27. Section2 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 3. Insert coefficients

  28. Section3 Classifying Chemical Reactions Chapter 8 Bellringer • Describe the following terms. • synthesis • decomposition • displacement

  29. Section3 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.

  30. Section3 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.

  31. Section3 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

  32. Visual Concepts Chapter 8 Combustion Reaction

  33. Section3 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)

  34. Visual Concepts Chapter 8 Synthesis Reactions

  35. Section3 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)

  36. Visual Concepts Chapter 8 Decomposition Reaction

  37. Visual Concepts Chapter 8 Electrolysis

  38. Section3 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.

  39. Section3 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

  40. Section3 Classifying Chemical Reactions Chapter 8 Displacement Reactions • In adisplacement reactiona single element reacts with a compound and displaces another element from the compound. • 2Al(s) + 3CuCl2(aq)  2AlCl3(aq) + 3Cu(s) • Aluminum displaces copper.

  41. Visual Concepts Chapter 8 Single Displacement Reaction

  42. Section3 Classifying Chemical Reactions Chapter 8 Displacement Reactions, continued • The activity seriesranks the reactivity of elements

  43. Visual Concepts Chapter 8 Activity Series

  44. Section3 Classifying Chemical Reactions Chapter 8 Displacement Reactions, continued Sample Problem E Determining Products by Using the Activity SeriesMagnesium is added to a solution of lead(II) nitrate. Will a reaction happen? If so, write the equation and balance it.

  45. Section3 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

  46. Section3 Classifying Chemical Reactions Chapter 8 Double-Displacement Reactions • In adouble-displacement reactiontwo 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)

  47. Visual Concepts Chapter 8 Double-Displacement Reaction

  48. Chapter 8 • Identifying Reactions and Predicting Products

  49. Standardized Test Preparation Chapter 8 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.

  50. Section4 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.

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