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Chapter 8 Chemical Equations Objectives: Be able to identify chemical equations Be able to identify chemical equations Write and balance chemical equations.

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Presentation on theme: "Chapter 8 Chemical Equations Objectives: Be able to identify chemical equations Be able to identify chemical equations Write and balance chemical equations."— Presentation transcript:

1 Chapter 8 Chemical Equations Objectives: Be able to identify chemical equations Be able to identify chemical equations Write and balance chemical equations Write and balance chemical equations Describe the information given in any chemical equation Describe the information given in any chemical equation Identify types of chemical equations Identify types of chemical equations Understand and describe the roles of heat in chemical reactions Understand and describe the roles of heat in chemical reactions

2 Chemical Reactions A chemical reaction is a process in which one or more substances are converted into new substances with different physical and chemical properties A chemical reaction is a process in which one or more substances are converted into new substances with different physical and chemical properties Why do chemical reactions occur? Why do chemical reactions occur?

3 The Chemical Equation In a chemical reaction atoms are neither created nor destroyed. All atoms present in the reactants must also be present in the products. In a chemical reaction atoms are neither created nor destroyed. All atoms present in the reactants must also be present in the products. Reactants: Reactants: Products: Products: Reactions involve Reactions involve

4 The Chemical Equation Word Equation: Word Equation: “reacts with” “reacts with” “yields” or “produces” “yields” or “produces” Example: Sodium metal reacts with chlorine gas to produce sodium chloride Example: Sodium metal reacts with chlorine gas to produce sodium chloride

5 The Chemical Equation Formula Equation (chemical equation): Formula Equation (chemical equation): Example: Sodium metal reacts with chlorine gas to produce sodium chloride Example: Sodium metal reacts with chlorine gas to produce sodium chloride

6 The Chemical Equation Magnesium reacts with nitrogen to produce magnesium nitride (remember diatomic molecules) Magnesium reacts with nitrogen to produce magnesium nitride (remember diatomic molecules) Silver (I) nitrate reacts with copper to form copper (II) nitrate and silver Silver (I) nitrate reacts with copper to form copper (II) nitrate and silver When heated, calcium carbonate decomposes to form calcium oxide and carbon dioxide When heated, calcium carbonate decomposes to form calcium oxide and carbon dioxide Ammonia reacts with hydrogen chloride to form ammonium chloride Ammonia reacts with hydrogen chloride to form ammonium chloride

7 The Chemical Equation Conditions required to carry out the reaction sometimes included Conditions required to carry out the reaction sometimes included, etc., etc. Physical state of substances often included Physical state of substances often included (s) = (s) = (l) = (l) = (g) = (g) = (aq) = (aq) = See table 8.1 See table 8.1

8 Writing and Balancing Equations Equations must be BALANCED Equations must be BALANCED Steps to follow: Steps to follow: 1. Write a word equation for the reaction 2. Write the

9 Writing and Balancing Equations 3. Balance the equation a. Count and compare b. Balance each element, one at a time, by placing whole numbers (coefficients) in front of the formulas c. Check all other elements and make adjustments as needed d. Do a final check – all atoms should be balanced a. a.

10 Writing and Balancing Equations Balance the following: Balance the following: Mg + N 2  Mg 3 N 2 AgNO 3 + Cu  Cu(NO 3 ) 2 + Ag CaCO 3  CaO + CO 2 NH 3 + HCl  NH 4 Cl

11 What Information Does an Equation Tell Us? What the What the The The The number of molecules or formula units of reactants and products in the reaction The number of molecules or formula units of reactants and products in the reaction The number of The number of

12 What Information Does an Equation Tell Us? P 4 O 10 + 12HClO 4  6Cl 2 O 7 + 4H 3 PO 4 P 4 O 10 + 12HClO 4  6Cl 2 O 7 + 4H 3 PO 4 We will use this information in Chapter 9… We will use this information in Chapter 9…

13 Types of Chemical Equations Reactions are classified based on how atoms or groups of atoms are rearranged during the reaction Reactions are classified based on how atoms or groups of atoms are rearranged during the reaction Book lists 4 types Book lists 4 types I want you to know 5 types I want you to know 5 types

14 Synthesis (Combination) Reaction Two (or more) substances combine to form a new compound Two (or more) substances combine to form a new compound ** Only ONE product***

15 Synthesis (Combination) Reaction Metal + Oxygen  Metal oxide Metal + Oxygen  Metal oxide Nonmetal + Oxygen  Nonmetal oxide Nonmetal + Oxygen  Nonmetal oxide Metal + Nonmetal  Salt Metal + Nonmetal  Salt Metal Oxide + Water  Metal hydroxide Metal Oxide + Water  Metal hydroxide Nonmetal Oxide + Water  Oxy-acid Nonmetal Oxide + Water  Oxy-acid

16 Decomposition Reaction A single compound reacts to give two or more substances A single compound reacts to give two or more substances Usually requires heat and/or a catalyst Usually requires heat and/or a catalyst

17 Decomposition Reaction Metal Oxides. Some decompose to yield free metal plus oxygen; others given another oxide, and some resist decomposition by heating Metal Oxides. Some decompose to yield free metal plus oxygen; others given another oxide, and some resist decomposition by heating Carbonates and hydrogen carbonates decompose to yield CO 2 when heated Carbonates and hydrogen carbonates decompose to yield CO 2 when heated Miscellaneous reactions in this category: Miscellaneous reactions in this category:

18 Single-Replacement Reaction An element reacts with a compound displacing an element from it An element reacts with a compound displacing an element from it If A is a metal, A will replace B to form AX, provided A is a more reactive metal than B If A is a metal, A will replace B to form AX, provided A is a more reactive metal than B If Y is a halogen, it will replace X to form BY, provided Y is a more reactive halogen than C If Y is a halogen, it will replace X to form BY, provided Y is a more reactive halogen than C Activity series can help make predictions Activity series can help make predictions Table 8.2 Table 8.2

19 Single-Replacement Reaction Metal + Acid  Hydrogen + Salt Metal + Acid  Hydrogen + Salt Metal + Water  Hydrogen + metal hydroxide or metal oxide Metal + Water  Hydrogen + metal hydroxide or metal oxide Metal + Salt  Metal + Salt Metal + Salt  Metal + Salt Halogen + Halide Salt  Halogen + Halide Salt Halogen + Halide Salt  Halogen + Halide Salt

20 Single-Replacement Reactions K, Ca, and Na K, Ca, and Na Mg, Al, Zn, and Fe Mg, Al, Zn, and Fe Ni, Sn, and Pb Ni, Sn, and Pb Cu, Ag, Hg, and Au do not displace hydrogen Cu, Ag, Hg, and Au do not displace hydrogen

21 Double-Replacement Reaction Appears to involve the exchange of parts of the reactions Appears to involve the exchange of parts of the reactions Ions of two compounds exchange places in an aqueous solution to form 2 new compounds Ions of two compounds exchange places in an aqueous solution to form 2 new compounds A precipitate (an insoluble solid compound formed during a reaction in solution) is often formed A precipitate (an insoluble solid compound formed during a reaction in solution) is often formed Heat may be produced Heat may be produced Gas bubbles may be produced Gas bubbles may be produced

22 Double-Replacement Reaction Neutralization of an acid and a base Neutralization of an acid and a base Formation of a precipitate Formation of a precipitate Metal oxide + acid  salt + water (and heat) Metal oxide + acid  salt + water (and heat)

23 Double-Replacement Reaction Formation of a gas Formation of a gas Gas can be produced indirectly Gas can be produced indirectly

24 Combustion Reactions A reaction of a substance with oxygen, usually with the rapid release of heat to produce a flame A reaction of a substance with oxygen, usually with the rapid release of heat to produce a flame Organic compounds (with carbon) usually produce CO 2 Organic compounds (with carbon) usually produce CO 2 If a compound contains hydrogen, water is a product If a compound contains hydrogen, water is a product

25 5 Types of Reactions Identify each: Identify each: AX + BY  AY + BX AX + BY  AY + BX A + B  AB A + B  AB A + BX  AX + B A + BX  AX + B AX  A + X AX  A + X Hydrocarbon + O 2  CO 2 + H 2 O Hydrocarbon + O 2  CO 2 + H 2 O

26 Heat in Chemical Reactions Energy changes always accompany chemical reactions Energy changes always accompany chemical reactions Exothermic reactions Exothermic reactions Endothermic reactions Endothermic reactions

27 Heat in Chemical Reactions Heat of Reaction Heat of Reaction Activation energy Activation energy See figures 8.1 & 8.2 See figures 8.1 & 8.2

28 Homework Finish Worksheets from Thursday Finish Worksheets from Thursday Paired Exercises #13, 19-21 Paired Exercises #13, 19-21 Additional Exercises #25 Additional Exercises #25


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