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Reactions. CH.3 Balancing Reactions Reaction Types. A Chemical Reaction. Reactants Products Types of Chemical reactions: There are many types of reactions but most can be classified into a few simple reactions types. How do you know a chemical reaction has occurred? .

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reactions

Reactions

CH.3

Balancing Reactions

Reaction Types

a chemical reaction
A Chemical Reaction
  • Reactants Products
  • Types of Chemical reactions:
  • There are many types of reactions but
  • most can be classified into a few simple
  • reactions types.
  • How do you know a chemical reaction has occurred?
chemical equations
Chemical equations
  • Chemist’s shorthand to describe a reaction.
  • It shows:
    • All reactants and products
    • The state of all substances
    • Any conditions used in the reaction
      • CaCO3 (s) CaO (s) + CO2 (g)

Reactant Products

A balanced equation shows the relationship

between the quantities of all reactants and products.

balancing chemical equations
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 Products
          • 1 Ca 1 Ca
          • 1 C 1 C
          • 3 O 3 O
balancing chemical equations5
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.
chemical changes
Chemical Changes

Temperature Changes

Light

Gas formation

Precipitation

Color changes

types of chemical reactions
Types of Chemical Reactions
  • Reactions involving electron transfer
    • synthesis or combination
    • decomposition
    • Electrochemical or single replacement
    • Combustion of hydrocarbons.
  • Reactions that involve rearrangement but not necessarily involve electron transfer
    • Metathesis or Double Substitution
    • Precipitation reactions and
    • Acid Base Reactions
  • Polymerization reaction
properties of aqueous solutions
Properties ofaqueous solutions
  • There are two general classes of solutes.
  • Electrolytic
    • ionic compounds in polar solvents
    • dissociate in solution to make ions
    • conduct electricity
    • may be strong (100% dissociation) or weak (less than 100%)
  • Nonelectrolytic
    • do not conduct electricity
    • solute is dispersed but does not dissociate
dissolving ionic compounds
Dissolving ionic compounds
  • When an ionic solid dissolves in water, the solvent removes ions from the crystal.
  • NaCl + H2O  Na+(aq) + Cl- (aq)
dissolving covalent compounds
Dissolving covalent compounds
  • Covalent compounds do not dissociate.
  • C6H12O6 C6H12O6 (aq)
ionic equations

H2O

H2O

Ionic equations
  • When ionic substances dissolve in water, they dissociate into ions.
  • AgNO3 Ag++ NO3-
  • KClK+ + Cl-
  • When a reaction occurs, only some of the ions are actually involved in the reaction.
  • Ag++ NO3- +K+ + Cl- AgCl(s) + K+ + NO3-
ionic equations12
Ionic equations
  • To help make the reaction easier to see, we commonly list only the species actually involved in the reaction.
  • Molecular equation
  • KCl + AgNO3AgCl(s) + KNO3
  • Full ionic equation
  • Ag++ NO3- +K+ + Cl- AgCl(s) + K+ + NO3-
  • Net ionic equation
  • Ag++Cl-AgCl(s)
  • NO3- and K+ are referred to as spectator ions.
some simple solubility rules
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.
metathesis reactions
Metathesis Reactions
  • Precipitation reactions
    • the formation of a solid upon mixing two solutions.
  • Gas formation
    • The formation of a gas when two mixtures are reacted
  • Acid Base titration
    • The neutralization of acids and bases to form a salt in water.
precipitation
Precipitation
  • NaCl + AgNO3 = AgCl (ppt) + NaNO3
  • Pb(NO3)2 + K2CrO4 = PbCrO4 (ppt) + KNO3
gas formation
Gas Formation
  • Vinegar + Baking soda = Carbon dioxide
  • CH3COOH + NaHCO3 = NaCH3COO + H2O + CO2
acid base neutralization
Acid Base Neutralization
  • Vinegar + Ammonia = Salt + water
  • CH3COOH + NH4OH = NH4CH3COO + H2O
common redox reactions
Common REDOX Reactions
  • Combustion
  • Corrosion
  • Photosynthesis
  • Kreb’s Cycle
  • Synthesis and Decomposition
  • Single Replacement
oxidation numbers and the periodic table
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
oxidation numbers
Oxidation Numbers
  • 1. 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.
identifying oxidation reduction reactions
Identifying oxidation-reduction reactions.
  • Oxidation-Reduction - REDOX
  • A 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 from

zero to +2. Cl has changed from zero to -1.

redox reactions
REDOX reactions
  • Oxidation
  • An increase in oxidation number.
  • Reduction
  • A 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) 2 Fe(NO3)2 (aq) + Zn(NO3)2 (aq)
half reactions
Half Reactions
  • The reactions that show the loss or gain of electrons.
  • 2 Mg + O2 2 MgO
  • What are the oxidation states of each of the atoms in the above reaction?
  • Mg  Mg+2
  • O2  2 O2-
oxidation
Oxidation
  • 2 Mg + O2 2 MgO
  • Mg  Mg+2
  • 12 p, 12 e 12 p, 10 e
  • Mg  Mg+2 + 2 e
  • The loss of electrons
single replacement reaction
Single replacement reaction
  • Where one element displaces another in a chemical compound.
  • H2 + CuO Cu + H2O
  • In 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.
synthesis reaction
Synthesis Reaction
  • The formation of a new compound from several substances
    • 2 H2 + O2 = 2 H2O
    • 2 Na + Cl2 = 2 NaCl
  • CaO (lime water) + CO2 = CaCO3 (s)
decomposition reactions
Decomposition Reactions
  • HgO = Hg + O2
  • H2O2= H2O + O2
  • with MnO2 catalyst
combustion
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 water
  • C8H18 + O2 = CO2 + H2O
  • Fe + O2 = Fe2O3 (rust)
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