you are experts at knowing the symbols of elements and using these symbols to write formulae. now we...

You are experts at knowing the symbols of elements and using these symbols to write formulae.Now we are going to use these concepts to describe chemical changes substances undergo. (aka chemical reactions)

A chemical reaction is the process by which one or more substances are changed into one or more DIFFERENT substances.

Bonds are broken and new bonds are formed, in other words, atoms are rearranged.

A chemical reaction is represented by a chemical equation, which is a shorthand method of saying what happens in a chemical reaction.

An equation shows two things: 

1. The change that takes place.2. Relative amounts of the various

elements and compounds that take part in these changes.

NOTATION:

REACTANTS YIELD PRODUCTS

2 C2H2(g) + 5 O2(g) 4 CO2(g) + 2 H2O(g)

s = solid g = gas l = liquidcr = crystalline aq = aqueous

To balance equations:• Determine the reactants and products from the problem.

• Assemble the equation. ( +and )

YOU MUST WRITE CORRECT FORMULAS!!!!!

• Balance the equation, according to the law of conservation of mass.

All atoms must be present and accounted for, NO A.W.O.L.’s.

Rules: 1.Remember the seven diatomic elements.2.Change only the coefficients, never the subscripts.

Hints:• Balance “lone” elements last.

• If a polyatomic ion is represented in both the products and reactants, balance the entire quantity and not each single atom.

• If OH1- and H1+ on one side of the equation and H2O on the other, change the formula of water to its structural formula H OH and balance the H and OH separately. H2OHOH

• In the combustion of hydrocarbons (compound containing C and H) begin balancing by placing a 2 in front of the hydrocarbon.

One final note: It is okay to use fractional coefficients,

though it is NOT PREFERRED, as long as

they do not split atoms.

Coefficients should be reduced if possible.

Classifying Chemical ChangesThere are hundreds of different kinds of chemical reactions, but many can be divided into 5 general categories.

Once we know the type of reaction, we can then predict the products of the reaction.

SynthesisCompositionCombination

DecompositionAnalysis

Single DisplacementSingle Replacement

Double DisplacementDouble ReplacementMetathesisCombustion

General Form: A + X AX

• Combination of 2 elements to form a binary compound

Composition

Metal and nonmetal

ONLY ONE PRODUCT

Tarnishing of silver silver reacts with sulfur

Ag(s) + S(s) Ag2S(s)2

binary ionic compound (salt)

General Form: A + X AX

• Combination of 2 elements to form a binary compound

Composition

Metal and nonmetal

Copper-bottomed pots copper reacts with oxygen

Cu(s) + O2(g) CuO(s)2

binary ionic compound (salt)

Cu(s) + O2(g) Cu2O(s)4

2

2

General Form: A + X AX

• Combination of 2 elements to form a binary compound

Composition

Metal and nonmetal

Rusting (oxidation of iron) iron reacts with oxygen

Fe(s) + O2(g) FeO(s)2

binary ionic compound (salt)

Fe(s) + O2(g) Fe2O3(s)4

2

23

H2O

H2O

General Form: A + X AX

• Combination of 2 elements to form a binary compound

Composition

Nonmetal and nonmetal

ONLY ONE PRODUCT

For the negative charge, pick the element with the greatest electronegativity (closest to Fluorine)

binary covalent compound

(molecule)

For the positive charge(s), determine the number of electrons to lose the p sublevel AND the number of electrons to lose the s and p sublevel

General Form: A + X AX

• Combination of 2 elements to form a binary compound

Composition

Nonmetal and nonmetal

binary covalent compound

(molecule)Burning sulfur sulfur reacts with oxygen

S(s) + O2(g) SO2(g)

S(s) + O2(g) SO3(g)2 23

General Form: A + X AX

• Combination of 2 elements to form a binary compound

Composition

Nonmetal and nonmetal

binary covalent compound

(molecule)Liquid bromine and gaseous chlorine

Br2(l) + Cl2(g) BrCl5(l)25

Br2(l) + Cl2(g) BrCl7(l)27

General Form: A + X AX

• Combination of 2 compounds

Composition

Metallic oxide and Nonmetallic oxide

ONLY ONE PRODUCT

The nonmetallic oxide determines the polyatomic ionIf the non-metal’s charge is “the higher charge” = -ateIf the non-metal’s charge is “the lower charge” = -ite

Ternary ionic compound

(salt with polyatomic ion)

To determine the overall formula, bond the metallic ion with the polyatomic ion.

General Form: A + X AX

• Combination of 2 compounds

Composition

Metallic oxide and Nonmetallic oxide

Ternary ionic compound

(salt with polyatomic ion)Li2O(s) + CO2(g) Li2CO3(s)

CaO(s) + SiO2(s) CaSiO3(s)

General Form: A + X AX

• Combination of 2 compounds

Composition

Metallic oxide and WATER

BASE(metal

with OH1-)

CaO(s) + H2O(l) Ca(OH)2(aq)

Na2O(s) + H2O(l) NaOH(aq)2

General Form: A + X AX

• Combination of 2 compounds

Composition

Nonmetallic oxide and WATER

OXYACID(H1+ and

polyatomic ion)The nonmetallic oxide determines the polyatomic ionIf the non-metal’s charge is “the higher charge” = -ateIf the non-metal’s charge is “the lower charge” = -ite

To determine the overall formula, bond the hydrogen ion with the polyatomic ion.

General Form: A + X AX

• Combination of 2 compounds

Composition

OXYACID(H1+ and

polyatomic ion)

CO2(s) + H2O(l) H2CO3 (aq)

SO3(s) + H2O(l) H2SO4 (aq)

Nonmetallic oxide and WATER

OXYACID(H1+ and

polyatomic ion)

OXYACID(H1+ and

polyatomic ion)

Nonmetallic oxide and WATER

OXYACID(H1+ and

polyatomic ion)

Acid Anhydride Acid

CO2 + H2O H2CO3

N2O3 + H2O 2 HNO2

N2O5 + H2O 2 HNO3

P2O3 + 3 H2O 2 H3PO3

P2O5 + 3 H2O 2 H3PO4

SO2 + H2O H2SO3

SO3 + H2O H2SO4

General Form: AX A + X

• Decomposition of a binary compound into 2 elements• ELECTROLYTIC DECOMPOSITION

• Industrial production of metals

Water

ONLY ONE REACTANT

H2(g) + O2(g)H2O(l)2 e-2

Molten Binary Salt

Mg(s) + Cl2(g)MgCl2(l)

e-

Decomposition

General Form: AX A + X

• Decomposition of a binary compound into 2 elements• THERMAL DECOMPOSITION (heat)

ONLY ONE REACTANT

KCl(s) + O2(g)KClO3(s)2 2

Metallic Chlorate Metallic chloride + oxygen

3

Decomposition

General Form: AX A + X

• Decomposition of a binary compound into 2 elements• THERMAL DECOMPOSITION (heat)

ONLY ONE REACTANT

BaO(s) + CO2(g)BaCO3(s)

Metallic CarbonateMetallic oxide + carbon dioxide

CaO(s) + CO2(g)CaCO3(s)

Decomposition

General Form: AX A + X

• Decomposition of a binary compound into 2 elements• THERMAL DECOMPOSITION (heat)

ONLY ONE REACTANT

Na2CO3(s) + H2O(g) + CO2(g)NaHCO3(s)

Metallic BicarbonateMetallic carbonate + water + carbon dioxide

2

Decomposition

General Form: AX A + X

• Decomposition of a binary compound into 2 elements• THERMAL DECOMPOSITION (heat)

ONLY ONE REACTANT

CaO(s) + H2O(g) Ca(OH)2(s)

Metallic HydroxideMetallic oxide + water

Base

Na2O(s) + H2O(g) NaOH(s)2

Decomposition

General Form: AX A + X

• Decomposition of a binary compound into 2 elements• THERMAL DECOMPOSITION (heat)

ONLY ONE REACTANT

CO2(g) + H2O(l) H2CO3(aq)

Oxyacids

Nonmetallic oxide + water

SO2(g) + H2O(l) H2SO3(aq)

SO3(g) + H2O(l) H2SO4(aq)

Decomposition

General Form: AX A + X

• Decomposition of a binary compound into 2 elements• THERMAL DECOMPOSITION (heat)

ONLY ONE REACTANT

Hg(l) + O2(g) HgO(s)

Metallic Oxides

Metal + oxygen

2 2

Decomposition

Single DisplacementSingle Replacement

General Form: A + BX AX + B

Element + Compound Element + Compound

If free element in the reactants forms cations, then it will replace the positive ion in the compound.

If free element in the reactants forms anions, then it will replace the negative ion in the compound.

The more reactive element must be bonded in the compound.

Single DisplacementSingle Replacement

General Form: A + BX AX + B

Element + Compound Element + Compound

The more reactive element must be bonded in the compound.

Al(s) + Fe2O3(s)2 Fe(l) + Al2O3(s)2

Cl2(g) + KBr(s)2 KCl(s) + Br2(l)2

General Form: AX + BY AY + BX

Compound + Compound Cmpd + Cmpd

Double ReplacementDouble Replacement or Metathesis

For a reaction to occur there must be the formation of:

A PRECIPITATE orA GAS orA MOLECULAR COMPOUND

General Form: AX + BY AY + BX

Compound + Compound Cmpd + Cmpd

Double ReplacementDouble Replacement or Metathesis

a PRECIPITATE – insoluble or slightly soluble

AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq)

General Form: AX + BY AY + BX

Compound + Compound Cmpd + Cmpd

Double ReplacementDouble Replacement or Metathesis

a GAS – insoluble that bubbles out of solution

Produced by the spontaneous decomposition of:

H2SO4(aq) + Na2CO3(aq) Na2SO4(aq) + H2CO3(aq)

Carbonic Acid into CO2 and H2O

H2SO4(aq) + Na2CO3(aq) Na2SO4(aq) + H2O(l) + CO2(g)

General Form: AX + BY AY + BX

Compound + Compound Cmpd + Cmpd

Double ReplacementDouble Replacement or Metathesis

a GAS – insoluble that bubbles out of solution

Produced by the spontaneous decomposition of:

HCl(aq) + Na2SO3(aq) NaCl(aq) + H2SO3(aq)

Sulfurous acid into SO2 and H2O

HCl(aq) + Na2SO3(aq) NaCl(aq) + H2O(l) + SO2(g)2 2

General Form: AX + BY AY + BX

Compound + Compound Cmpd + Cmpd

Double ReplacementDouble Replacement or Metathesis

a GAS – insoluble that bubbles out of solution

Produced by the spontaneous decomposition of:

NH4Cl(s) + NaOH(aq) NaCl(aq) + NH4OH(aq)

Ammonium Oxide or Ammonium Hydroxide

NH4Cl(s) + NaOH(aq) NaCl(aq) + H2O(l) + NH3(g)

into NH3 and H2O

General Form: AX + BY AY + BX

Compound + Compound Cmpd + Cmpd

Double ReplacementDouble Replacement or Metathesis

a GAS – insoluble that bubbles out of solution

Production of BINARY ACID (VOLATILE ACID)

NaCl(s) + H2SO4(aq) HCl(g) + Na2SO4(aq)2 2

FeS(s) + HCl(aq) H2S(g) + FeCl2(aq)2

General Form: AX + BY AY + BX

Compound + Compound Cmpd + Cmpd

Double ReplacementDouble Replacement or Metathesis

a MOLECULAR COMPOUND – like water or ammonia

HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l)

Molecular, Complete Ionic, and

Net Ionic Equations

HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l)

Double Displacement reactions can be written in several forms.

Complete Molecular

Complete IonicThis shows the dissociation of soluble ionic

compounds and strong acids.

Molecular, Complete Ionic, and

Net Ionic Equations

HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l)

Complete IonicThis shows the dissociation of soluble ionic

compounds and strong acids.

H1+(aq) + Cl1-

(aq) + Na1+(aq) + OH1-

(aq) Na1+(aq) + Cl1-

(aq) + H2O(l)

Molecular, Complete Ionic, and

Net Ionic EquationsNet IonicIons that occur on both sides of the reaction do not participate directly in the reaction. They are called SPECTATOR IONS, and can be removed from the complete ionic equation.

H1+(aq) + Cl1-

(aq) + Na1+(aq) + OH1-

(aq) Na1+(aq) + Cl1-

(aq) + H2O(l)

H1+(aq) + OH1-

(aq) H2O(l)

Rules for DissociationStrong Acids are to be dissociated, while weak ones are not

Binary: HCl, HBr, HI, HF is weak

Ternary: The number of oxygen exceeds the hydrogen

atoms by two or more.Strong Weak

HCl HCN

HClO3 HClO

HClO4 HC2H3O2

H2SO4 H2SO3

HNO3 HNO2

H2SeO4 H2CO3

Rules for DissociationStrong Bases dissociate (hydroxides), weak ones do not

Salts dissociate if soluble; if not leave undissociated.

Oxides are either solids or gases; therefore do not dissociate.

Strong Weak

NaOH NH3

Neutralization and Combustion

Neutralization is a common form of a metathesis reaction

that produces water.

HNO3(aq) + KOH(aq) KNO3(aq) + H2O(l)

Acid + Base Binary/ternary salt + water

HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l)

Neutralization and Combustion

The general definition of a combustion reaction is one in which oxygen is a reactant. Specifically, when oxygen reacts with a hydrocarbon to produce carbon dioxide and water.

CH4(g) + O2(g) CO2(g) + H2O(g)

Hydrocarbon and oxygen

Carbon dioxide and water

2 2

C8H18(g) + O2(g) CO2(g) + H2O(g)25 182 16

Neutralization and Combustion

The general definition of a combustion reaction is one in which oxygen is a reactant. Specifically, when oxygen reacts with a hydrocarbon to produce carbon dioxide and water.Hydrocarbon and

oxygenCarbon dioxide and

water

If N is part of the hydrocarbonNO2 is produced too!

If S is part of the hydrocarbonSO2 is produced too!

Neutralization and Combustion

The general definition of a combustion reaction is one in which oxygen is a reactant. Specifically, when oxygen reacts with a hydrocarbon to produce carbon dioxide and water.Hydrocarbon and

oxygenCarbon dioxide and

water

Incomplete combustion…. Oxygen is lacking

CO is produced instead of CO2!!

Hydrocarbon and oxygen

Carbon monoxide and water

COMPLETE

INCOMPLETE