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