Presentation on theme: "Chemical Equations & Reactions Chapter 8. Objectives List observations that suggest that a chemical reaction has taken place. List three requirements."— Presentation transcript:
Objectives List observations that suggest that a chemical reaction has taken place. List three requirements for a correctly written chemical equation. Write a word equation and a formula equation for a given chemical reaction. Balance a formula equation by inspection.
Chemical Reaction Process by which one or more substances are changed into one or more different substances
Indications of a Chemical Reaction 1. Evolution of heat & light
Indications of a Chemical Reaction 2. Production of a gas
Indications of a Chemical Reaction 3. Formation of a precipitate
Precipitate A solid that is produced as a result of a chemical reaction in solution & that separates from the solution
Indications of a chemical reaction 4. Change in color. (sumac leaves change color when chlorophyll is destroyed)
Chemical Equation Representation, with symbols and formulas, of the identities and relative amounts of the reactants and products in a chemical reaction Reactants Products Follows the Law of Conservation of Mass
Characteristics of Chemical Equations The equation must represent known facts The equation must contain the correct formulas for the reactants & products The law of conservation of mass must be satisfied- which means the same # and type of atoms are present on both sides of the equation.
Word Equation Represents facts- only qualitative Example: Methane + oxygen carbon dioxide + water Writing Chemical Equations
Example: CH 4(g) + O 2(g) CO 2(g) + H 2 O (g) (not balanced) Symbols you will see in equations pg.266 Formula Equation Writing Chemical Equations
Inserting Coefficients-small whole # that appears in front of a formula Multiplies number of atoms of each element indicated in chemical formula Example: CH 4(g) + 2O 2(g) CO 2(g) + 2H 2 O (g) Balanced Formula Equation Writing Chemical Equations
Balancing Chemical Equations Balance the formula equation according to the law of conservation of mass Balance the different types of atoms one at a time Balance polyatomic ions that appear on both sides of the equation as single units Balance H atoms and O atoms after atoms of all other elements have been balanced
Examples Mg + HCl MgCl 2 + H 2 Al 2 (SO 4 ) 3 + Ca(OH) 2 Al(OH) 3 + CaSO 4 MgI 2 + KNO 3 KI + Mg(NO 3 ) 2
Writing and Balancing Equations from Word Equations 1. Write out correct chemical formulas and symbols. 2. Balance equation. Solid aluminum metal combines with oxygen gas to produce solid aluminum oxide
Writing equations from word equations Examples to try. 1. Solid calcium metal reacts with water to form aqueous calcium hydroxide and hydrogen gas. 2. Solid iron(III)oxide and carbon monoxide gas produces solid iron and carbon dioxide gas. 3. Solid copper reacts with aqueous silver nitrate to produce aqueous copper (II) nitrate and solid silver.
Objectives Define & give general equations for synthesis, decomposition, single- replacement, and double-replacement reactions. Classify a reaction as synthesis, decomposition, single displacement, double displacement or combustion. Predict the products of simple reactions if given the reactants.
Synthesis Reactions A reaction in which two or more substances combine to form a new compound A + X AX A and X are elements or compounds AX is a compound
Synthesis Reactions Examples: magnesium + oxygen __________ iron + oxygen __________ calcium oxide + water __________
Decomposition Reactions A reaction in which a single compound produces two or more simpler substances Opposite of synthesis reactions AX A + X AX is a compound A and X are elements or compounds
Decomposition Reactions (Binary Compounds) Decomposition of a binary compound into its elements. Example: water __________ + __________
Electrolysis The decomposition of a substance by an electric current
Decomposition Reactions (Metal Carbonates) Metal carbonates decompose to produce a metal oxide & carbon dioxide gas. Example: calcium carbonate ______ + ______
Decomposition Reactions (Metal Hydroxides) Metal hydroxides (except group 1 metals) decompose to produce metal oxides & water. Example: calcium hydroxide ______ + ______
Single-Replacement Reactions A reaction in which one element replaces a similar element in a compound A + BX AX + B - or – Y + BX BY + X A, B, X, Y are elements AX, BX, BY are compounds
Single-Replacement Reactions (Replacement of a Metal or Nonmetal) Example: aluminum + lead nitrate ____ + ____ fluorine + sodium chloride ____ + ____
Double-Replacement Reactions A reaction in which the ions of two compounds exchange places in an aqueous solution to form two new compounds AX + BY AY + BX A, X, B, Y in reactants represent ions AY & BX represent ionic or molecular compounds
Double-Replacement Reactions (Formation of a Precipitate) One cation of one reactant combine with the anions of another reactant to form insoluble or slightly soluble compound Example: Potassium iodide + lead (II) nitrate ____ + ____
Double-Replacement Reactions (Formation of a Gas) Example: Iron(II) sulfide + hydrochloric acid ____ + ____
Combustion Reactions A reaction in which a substance combines with oxygen, releasing a large amount of energy in the form of light and heat Combustion of a hydrocarbon always yield carbon dioxide and water.
Try this: Write a balanced chemical equation for the following reaction: Ethyl alcohol (C 2 H 5 OH) burns to produce carbon dioxide and water.
Objectives Explain the significance of an activity series. Use an activity series to predict whether a given reaction will occur and what the products will be.
Activity Series A list of elements organized according to the ease with which the elements undergo certain chemical reactions Used to help predict whether certain chemical reactions will occur
Activity Series Table 8.3, p. 286 An element can replace any element below it but not above it Based on experiment Will be given to you on test.
Examples Using the activity series, predict whether each of the possible reactions will occur. For the reactions that will occur, write the products & balance the equation. Ba (s) + H 2 O (l) Cu (s) + HBr (aq) Al (s) + HBr (aq) F 2(g) + NaCl (s)