Chapter 8: Chemical Equations and Reactions 1.List signs of a chemical change 2.Correctly write a chemical equation 3.Balance a chemical equation

Indications of Chemical Reaction Temperature change Formation of a gas Formation of a precipitate (insoluble) Color change

Chemical Equations Represent known facts Contain correct formulas for reactants and products Satisfies law of conservation of mass Subscripts can NEVER be changed Coefficients CAN be changed

Word and Formula Equations Word Equation methane + oxygen  carbon dioxide + water Formula Equation CH 4 (g) + O 2 (g)  CO 2 (g) + H 2 O(g)

Additional Symbols → - “yields” ↔ - reversible reaction ↑ - gaseous product; also (g) ↓ - precipitate (s) – solid ( l ) – liquid (aq) – aqueous; dissolved in water

Meaning of a Chemical Equation 1.Coefficients represent relative amounts of reactants 2.Relative masses of reactants and products can be determined from coefficients 3.The reverse reaction has the same relative amounts of substances as forward reaction

Balancing Equations Balance elements one at a time Balance polyatomic ions as single units Balance atoms that appear only once on each side first Balance hydrogen and oxygen last

Types of Reactions 1.Give general equations for types of reactions 2.Classify reactions 3.List 3 types of synthesis and 6 decomposition reactions 4.List 4 types of single- replacement and 3 types of double- replacement reactions 5.Predict products of reactions given the reactants

Synthesis Reactions General Formula: A + X  AX

Synthesis with Oxygen With metals form metal oxides Ex – Mg(s) + O 2 (g)  MgO(s) K(s) + O 2 (g)  K 2 O(s) 2Fe(s) + O 2 (g)  2FeO(s) 4Fe(s) + 3O 2 (g)  2Fe 2 O 3 S 8 (s) + 8O 2 (g)  8SO 2 (g) C(s) + O 2 (g)  CO 2 (g)

Synthesis with Sulfur With metals produce metal sulfides Ex-16Rb(s) + S 8 (s)  8Rb 2 S(s) 8Ba(s) + S 8 (s)  8BaS(s)

Metals with Halogens Group 1: M + X 2  2MX Ex – Na(s) + Cl 2 (g)  2NaCl(s) Group 2: M + X 2  MX 2 Ex – Mg(s) + F 2 (g)  MgF 2 (s)

Metal Oxides with Water Group 1 & 2 form hydroxides Ex – K 2 O(s) + H 2 O(l)  2KOH(aq) CaO(s) + H 2 O(l)  Ca(OH) 2 (l)

Non-metal Oxide with Water Form oxyacids Ex – SO 2 (g) + H 2 O(l)  H 2 SO 3 (aq) P 2 O 5 (s) + 3H 2 O(l)  2H 3 PO 4 (aq)

Decomposition Reactions AX  A + X

Decomposition of Binary Compounds Breaks down into its elements Process called electrolysis

Decomposition of Metal Carbonates Form metal oxides and carbon dioxide

Decomposition of Metal Hydroxides Form metal oxides and water

Decomposition of Acids Break down into non-metal oxides and water

Single Replacement General Formula A + BX  AX + B

Metal Replaces Another Metal Aluminum is more reactive than lead

Replacement of Hydrogen in Water by a Metal More Active Metals Less Active Metals

Replacement of Hydrogen in an Acid by a Metal Metals more active than hydrogen

Replacement of Halogens Each halogen can replace the halogen below it on the periodic table

Double Replacement AX + BY  AY + BX Formation of a precipitate Formation of a gas Formation of water

Formation of a Precipitate An insoluble product forms

Formation of a Gas Insoluble gas forms Example

Formation of Water Water forms during reaction

Combustion Reaction Substance reacts with oxygen to release heat and light Products are often carbon dioxide and water

Neutralization Reaction HA + BOH  AB + HOH Usually these are acid-base reactions Products include salt and water

Types of Rxn Lab Due Friday That’s if you’re wondering…

Activity Series 1.Explain the significance of an activity series 2.Use an activity series to predict if a reaction will take place

Metals vs. Nonmetals Greater activity of a metal indicates how easily it loses electrons Greater activity of a nonmetal indicates how easily it gains electrons In a single-replacement reaction, if an element with lower activity is to be replaced, the reaction will take place.