2 A Chemical Reaction Reactants Products Types of Chemical reactions: There are many types of reactions butmost can be classified into a few simplereactions types.How do you know a chemical reaction has occurred?
3 Chemical equations Chemist’s shorthand to describe a reaction. It shows:All reactants and productsThe state of all substancesAny conditions used in the reactionCaCO3 (s) CaO (s) CO2 (g)Reactant ProductsA balanced equation shows the relationshipbetween the quantities of all reactants and products.
4 Balancing chemical equations Each side of a chemical equation must have the same number of each type of atom.CaCO3 (s) CaO (s) + CO2 (g)Reactants Products1 Ca Ca1 C C3 O O
5 Balancing chemical equations Step 1 Count the number of atoms of each element on each side of the equation.Step 2 Determine which atom numbers are not balanced.Step 3 Balance one atom at a time by using coefficients in front of one or more substances.Step 4 Repeat steps 1-3 until everything is balanced.
6 Chemical Changes Temperature Changes Light Gas formation Precipitation Color changes
7 Types of Chemical Reactions Reactions involving electron transfersynthesis or combinationdecompositionElectrochemical or single replacementCombustion of hydrocarbons.Reactions that involve rearrangement but not necessarily involve electron transferMetathesis or Double SubstitutionPrecipitation reactions andAcid Base ReactionsPolymerization reaction
8 Properties of aqueous solutions There are two general classes of solutes.Electrolyticionic compounds in polar solventsdissociate in solution to make ionsconduct electricitymay be strong (100% dissociation) or weak (less than 100%)Nonelectrolyticdo not conduct electricitysolute is dispersed but does not dissociate
9 Dissolving ionic compounds When an ionic solid dissolves in water, the solvent removes ions from the crystal.NaCl + H2O Na+(aq) + Cl- (aq)
10 Dissolving covalent compounds Covalent compounds do not dissociate.C6H12O6 C6H12O6 (aq)
11 Ionic equationsWhen ionic substances dissolve in water, they dissociate into ions.AgNO Ag+ + NO3-KCl K+ + Cl-When a reaction occurs, only some of the ions are actually involved in the reaction.Ag+ + NO K+ + Cl AgCl(s) + K+ + NO3-H2OH2O
12 Ag+ + NO3- + K+ + Cl- AgCl(s) + K+ + NO3- Ionic equationsTo help make the reaction easier to see, we commonly list only the species actually involved in the reaction.Molecular equationKCl + AgNO3 AgCl(s) + KNO3Full ionic equationAg+ + NO K+ + Cl AgCl(s) + K+ + NO3-Net ionic equationAg+ + Cl AgCl(s)NO3- and K+ are referred to as spectator ions.
13 Some simple solubility rules All acids are soluble.All Na+, K+ and NH4+ salts are soluble.All nitrate and acetate salts are soluble.All chlorides except AgCl and Hg2Cl2 are soluble. PbCl2 is slightly soluble.All sulfates are soluble except PbSO4, Hg2SO4, SrSO4 and BaSO4. Ag2SO4 and CaSO4 are slightly soluble.All sulfides are insoluble except those of the Group IA (1), IIA (2) and ammonium sulfide.All hydroxides are insoluble except those of the group IA(1) and Ba(OH)2. Sr(OH)2 and Ca(OH)2 are slightly soluble.
14 Metathesis Reactions Precipitation reactions the formation of a solid upon mixing two solutions.Gas formationThe formation of a gas when two mixtures are reactedAcid Base titrationThe neutralization of acids and bases to form a salt in water.
16 Gas Formation Vinegar + Baking soda = Carbon dioxide CH3COOH + NaHCO3 = NaCH3COO + H2O + CO2
17 Acid Base Neutralization Vinegar + Ammonia = Salt + waterCH3COOH + NH4OH = NH4CH3COO + H2O
18 Common REDOX Reactions CombustionCorrosionPhotosynthesisKreb’s CycleSynthesis and DecompositionSingle Replacement
19 Oxidation numbers and the periodic table Some observed trends in compounds.Metals have positive oxidation numbers.Transition metals typically have more than one oxidation number.Nonmetals and semimetals have both positive and negative oxidation numbers.No element exists in a compound with an oxidation number greater than +8.The most negative oxidation numbers equals 8 - the group number
20 Oxidation Numbers1. An atom in its elemental state has an oxidation number of 0.2. An atom in a monatomic ion has an oxidation number identical to its charge.3. An atom in a polyatomic ion or in a molecular compound usually has the same oxidation number it would have it were a monatomic ion.4. The sum of the oxidation numbers is 0 for a neutral compound and equal to the net charge for a polyatomic ion.
21 Identifying oxidation-reduction reactions. Oxidation-Reduction - REDOXA chemical reaction where there is a net change in the oxidation number of one or more species.Both an oxidation and a reduction must occur during the reaction.Mg (s) + Cl2 (g) MgCl2 (s)Here the oxidation number of Mg has changed fromzero to +2. Cl has changed from zero to -1.
22 2 Fe(NO3)3 (aq) + Zn(s) 2 Fe(NO3)2 (aq) + Zn(NO3)2 (aq) REDOX reactionsOxidationAn increase in oxidation number.ReductionA decrease in oxidation number.If the oxidation number of any element changes in the course of a reaction, the reaction is oxidation-reduction.Example.2 Fe(NO3)3 (aq) + Zn(s) Fe(NO3)2 (aq) + Zn(NO3)2 (aq)
23 Half Reactions The reactions that show the loss or gain of electrons. 2 Mg + O2 2 MgOWhat are the oxidation states of each of the atoms in the above reaction?Mg Mg+2O2 2 O2-
24 Oxidation 2 Mg + O2 2 MgO Mg Mg+2 12 p, 12 e 12 p, 10 e Mg Mg eThe loss of electrons
25 Single replacement reaction Where one element displaces another in a chemical compound.H2 + CuO Cu + H2OIn this example, hydrogen replaces copper.This type of reaction always involves oxidation and reduction (REDOX).Since one species is replacing another, there are no spectator ions.
30 1774: Antoine Lavoisier solves the question of the burning process and chemical processes
31 Combustion The burning of a substance in the presence of oxygen. Gasoline burns when oxygen is taken into your engine, the products of the reaction are carbon dioxide and waterC8H O2 = CO2 + H2OFe + O2 = Fe2O3 (rust)