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REACTIONS IN AQUEOUS SOLUTIONS:
Predicting whether a reaction will occurReactions with a solid productDescribing reactions in aqueous solutionsReactions that form water: Acids and BasesReactions of metals with non-metals (Oxidation-Reduction Reactions)Classification of reactionsOther classifications
Homework Problems:7.1: 2 7.2: 3, 4, 9, 10, 11, 13, 21, 227.3: 25, 267.4: 397.5: 507.6: 547.7: 61, 64, 66
REACTIONS IN AQUEOUS SOLUTIONS:
Predicting whether a reaction will occur
JUST BECAUSE A REACTION IS POSSIBLE DOES NOT NECESSARILY MEAN IT WILL OCCUR.
THERE ARE TWO ISSUES: 1. WHETHER A REACTION “WANTS TO OCCUR”
Paper + oxygen carbon dioxide + water
Reactants Products
2. WHETHER SUFFICIENT ENERGY IS PRESENT TO START THE PROCESS
SOME POTENTIAL DRIVING FORCES*Formation of a solid*Formation of (removable) water*Transfer of electrons*Formation of a gas
REACTIONS IN AQUEOUS SOLUTIONS:Reaction is which a solid forms
One driving force is formation of a solid:PRECIPITATION
Precipitate
CHEMICAL CHANGE OCCURRED.WHAT CHEMICAL REACTION FORMULA DESCRIBES
WHAT HAPPENED
Break the problem up:Reactant entities known.What happens when these dissolve in water?What possible products could form?Can we guess what the precipitate might be?Are there rules to guide us on what precipitates?
KCl (aq) + AgNO3 (aq)Colorless Colorless
REACTIONS IN AQUEOUS SOLUTIONS:Reactants dissolving in water
The starting solids are ionic compounds.
They are neutral.
When dissolved in water, they separate and the individual ions move around separately.
This can be demonstrated through in creased conductivity of water that they are dissolved in.
STRONG ELECTROLYTE: Substance which when dissolved in water increases conductance of water.
KCl (aq) + AgNO3 (aq)Colorless Colorless
ADDITIONAL EXAMPLES INAQUEOUS SOLUTIONS:Reactants dissolving in water
KCl (aq) + AgNO3 (aq)Colorless Colorless
K+
K+ K+
K+
Cl-
Cl-
Ag+ NO3-
NO3-
Ions separate.Ratios of ions determined by original compound
K+ (aq)+ Cl- (aq)+Ag+(aq)+NO3-(aq)
Ag+
Cl-
Cl-
REACTIONS IN AQUEOUS SOLUTIONS:
How to decide what products form
K+
Cl-
Ag+
NO3-
KNO3 KCl
Ag NO3 AgCl
Likely precipitate
Like charged ions don’t combineStarting solutions do not precipitateProducts have net charge of zeroThink of possible verification experiments
KCl (aq) + AgNO3 (aq)Colorless Colorless
K+ (aq)+ Cl- (aq)+Ag+(aq)+NO3-(aq)
REACTIONS IN AQUEOUS SOLUTIONS:
Final Description
AgCl (s) + KNO3 (aq) White Colorless
K+
K+NO3
-
NO3-
AgClAgCl
KCl (aq) + AgNO3 (aq)Colorless Colorless
REACTIONS IN AQUEOUS SOLUTIONS:Reaction is which a solid forms
One driving force is formation of a solid:PRECIPITATION
Yellow Precipitate
CHEMICAL CHANGE OCCURRED.WHAT CHEMICAL REACTION FORMULA DESCRIBES
WHAT HAPPENED
Break the problem up:Reactant entities known.What happens when these dissolve in water?What possible products could form?Can we guess what the precipitate might be?Are there rules to guide us on what precipitates?
K2CrO4(aq) + Ba(NO3 )2 (aq)Yellow Colorless
REACTIONS IN AQUEOUS SOLUTIONS:Reactants dissolving in water
The starting solids are ionic compounds.
They are neutral.
When dissolved in water, they separate and the individual ions move around separately.
This can be demonstrated through in creased conductivity of water that they are dissolved in.
STRONG ELECTROLYTE: Substance which when dissolved in water increases conductance of water.
K2CrO4(aq) + Ba(NO3 )2 (aq) Yellow Colorless
ADDITIONAL EXAMPLES INAQUEOUS SOLUTIONS:Reactants dissolving in water
K+
K+ K+
K+
CrO42- Ba2+ NO3
-
Ions separate.Ratios of ions determined by original compound
2K+ (aq)+ CrO42-(aq)+Ba2+(aq)+2NO3
-(aq)
K2CrO4(aq) + Ba(NO3 )2 (aq) Yellow Colorless
CrO42-
Ba2+
NO3-
NO3-
NO3-
REACTIONS IN AQUEOUS SOLUTIONS:
How to decide what products form
K+
CrO42-
Ba2+
NO3-
KNO3 K2CrO4
BaNO3 BaCrO4
Likely precipitate
Like charged ions don’t combineStarting solutions do not precipitateProducts have net charge of zeroThink of possible verification experiments
K2CrO4(aq) + Ba(NO3 )2 (aq) Yellow Colorless
2K+ (aq)+ CrO42-(aq)+Ba2+(aq)+2NO3
-(aq)
REACTIONS IN AQUEOUS SOLUTIONS:
Final Description
BaCrO4(s) + 2KNO3 (aq) Yellow Colorless
K+
K+NO3
-
NO3-
BaCrO4
K2CrO4(aq) + Ba(NO3 )2 (aq) Yellow Colorless
DESCRIBING REACTIONS IN AQUEOUS SOLUTIONS:
Observation:
Molecular Equation:
Complete Ionic Equation:
Net Ionic Equation:
2K+ (aq)+ CrO42-(aq)+Ba2+(aq)+2NO3
-(aq)BaCrO4(s) + 2K+ (aq)+ 2NO3
-(aq)
K2CrO4(aq) + Ba(NO3 )2 (aq)BaCrO4(s) + 2KNO3 (aq)
Ba2+(aq) + CrO42-(aq) BaCrO4(s)
K2CrO4(aq) + Ba(NO3 )2 (aq) Yellow Colorless
Yellow Precipitate
SPECTATOR IONS
ADDITIONAL EXAMPLES INAQUEOUS SOLUTIONS:Reactants dissolving in water
Na+
Na+ Na+
Na+
SO42- Pb2+ NO3
-
Ions separate.Ratios of ions determined by original compound
2Na+ (aq)+ SO42-(aq)+Pb2+(aq)+2NO3
-(aq)
Na2SO4(aq) + Pb(NO3 )2 (aq)
SO42-
Pb2+
NO3-
NO3-
NO3-
REACTIONS IN AQUEOUS SOLUTIONS:
How to decide what products form
Na+
SO42-
Pb2+
NO3-
NaNO3 Na2SO4
PbNO3 PbSO4
Likely precipitate
Like charged ions don’t combineStarting solutions do not precipitateProducts have net charge of zeroThink of possible verification experiments
Na2SO4(aq) + Pb(NO3 )2 (aq)
2Na+ (aq)+ SO42-(aq)+Pb2+(aq)+2NO3
-(aq)
REACTIONS IN AQUEOUS SOLUTIONS:
Final Description
PbSO4(s) + 2NaNO3 (aq) Precipitate Colorless
Na+
Na+NO3
-
NO3-
PbSO4
Na2SO4(aq) + Pb(NO3 )2 (aq)
DESCRIBING REACTIONS IN AQUEOUS SOLUTIONS:
Observation:
Molecular Equation:
Complete Ionic Equation:
Net Ionic Equation:
2Na+ (aq)+ SO42-(aq)+Pb2+(aq)+2NO3
-(aq)PbSO4(s) + 2Na+ (aq)+ 2NO3
-(aq)
Na2SO4(aq) + Pb(NO3 )2 (aq)PbSO4(s) + 2NaNO3 (aq)
Pb2+(aq) + SO42-(aq) PbSO4(s)
Na2SO4(aq) + Pb(NO3 )2 (aq)
Precipitate
SPECTATOR IONS
REACTIONS THAT FORM WATER:ACIDS AND BASES
TWO VERY IMPORTANT CLASSES OF COMPOUNDS.
Mineral acids known as far back as the 1300In late 1800s, Arrhenius proposed that….
An acid is a substance that produces H+ ions (protons) when it is dissolved in water.
Strong acids dissociate completely into protons and the counter anion (Stong electrolytes).
HCl (g) H+ (aq) + Cl-(aq)
HNO3 H+ (aq)+ NO3-(aq)
H2SO4 H+ (aq)+ HSO4-(aq)
REACTIONS THAT FORM WATER:ACIDS AND BASES
TWO VERY IMPORTANT CLASSES OF COMPOUNDS.
A Base is a substance that produces OH- ions (hydroxide ions) when it is dissolved in water.
Strong bases dissociate completely into hydroxide ions and the counter cation.
NaOH (s) Na+ (aq) + OH-(aq)
KOH (s) K+ (aq)+ OH-(aq)
ACIDS and BASES
Dissolved in water
H+
H+ H+
H+
Cl- Na+
Ions separate.Ratios of ions determined by original compound
HCl (aq) + NaOH (aq)
Cl-OH-
Cl-
Cl-
OH-
OH-
OH-
Na+
Na+
Na+
ACID-BASE REACTIONS IN AQUEOUS SOLUTIONS:
H+
Cl-
Na+
OH-
H2O HCl
NaOH NaCl
Like charged ions don’t combineStarting solutions do not precipitateProducts have net charge of zero
HCl (aq) + NaOH (aq)Colorless Colorless
H+ (aq)+ OH- (aq)+Na+(aq)+Cl-(aq)
DESCRIBING REACTIONSBETWEEN ACIDS AND BASES
Observation:
Molecular Equation:
Complete Ionic Equation:
Net Ionic Equation:
H+ (aq) + Cl-(aq) + Na+(aq) + OH-(aq)H2O (l) + Na+ (aq) + Cl-(aq)
HCl(aq) + NaOH(aq)NaCl(aq) + H2O (l)
H+ (aq) + OH-(aq) H2O (l)
Note salt formation!
HCl (aq) + NaOH (aq) Colorless Colorless
Colorless
SPECTATOR IONS
DESCRIBING REACTIONSBETWEEN ACIDS AND BASES
Observation:
Molecular Equation:
Complete Ionic Equation:
Net Ionic Equation:
H+ (aq) + NO3-(aq) + K+(aq) + OH-(aq)
H2O (l) + K+ (aq) + NO3-(aq)
HNO3 (aq) + KOH(aq)KNO3 (aq) + H2O (l)
H+ (aq) + OH-(aq) H2O (l)
HNO3 (aq) + KOH (aq) Colorless Colorless
Colorless
SPECTATOR IONS
Note salt formation!
REACTIONS OF METALS WITH NON-METALS
(OXIDATION-REDUCTION REACTIONS):TO LEARN GENERAL CHARACTERISTICS OF A REACTION
BETWEEN A METAL AND A NON-METAL
TO RECOGNIZE ELECTRON TRANSFER AS A DRIVING FORCE FOR A CHEMICAL REACTION
23
Na11
23
Na+
11
11-
NeutralSodiumAtom
11+ 11+
10-
SodiumIon
IONIZATION OF SODIUM
Na Na+ + e-
9-
9+ 9+
10-
FluorineAtom
FluorideIon
19
F9
19
F-
9
IONIZATION OF FLUORINE
F + e- F-
11-
11+
SodiumAtom
9-
9+
Fluorine Atom
e-
10-
11+
SodiumIon(+)
10-
9+
Fluorine Ion(-)
AN OXIDATION-REDUCTION REACTION
2Na + F2 2 NaF
+
2Mg(s) + O2(g) 2MgO(s)
Mg Mg 2+ + 2e-
O + 2e- O 2-
Examples of Oxidation-Reduction Reactions
Mg
Mg
O
O
2e-
2e-
Mg 2+
Mg 2+
O 2-
O 2-
2Al(s) + Fe2O3(s) 2Fe(s) + Al2O3(s)
Examples of Oxidation-Reduction Reactions
Al Al 3+ + 3e-
Fe 3+
+ 3e- Fe
Al
Al
O O
Al 3+
Al 3+
O
Fe 3+
Fe 3+
O O O
Fe
Fe3e-
3e-
2Al(s) + 3I2(s) 2Al I3(s)
Examples of Oxidation-Reduction Reactions
Al Al 3+ + 3e-
I + e- I-
Al
Al
I IAl 3+
Al 3+
I I
I I
I -
I -
I -
I -
I -
I -
CLASSIFICATION SCHEMES FOR REACTIONS:
One Approach
FORMATION OF A SOLID
FORMATION OF WATER
TRANSFER OF ELECTRONS
K2CrO4 + Ba(NO3 )2 BaCrO4 + 2KNO3
Solution Solution Solid Solution
Precipitation ReactionDouble displacement Reaction
HCl + NaOH NaCl + H2O
Solution Solution Solution Liquid
Acid-Base Reaction
2Na + F2 2 NaF
Solid Gas Solid
Oxidation-Reduction Reaction
FORMATION OF A GAS
2HCl + Na 2CO3 CO2 + H2O + NaCl
Solution Solution Gas Liquid Solution
CLASSIFICATION SCHEMES FOR REACTIONS:
Another Approach
COMBUSTION REACTIONS
SYNTHESIS (COMBINATION) REACTIONS
DECOMPOSITION REACTIONS
C3H8 + 5 O2 3 CO2 + 4H2OPropane Gas Gas Gas Gas
C8H18 + 25 O2 16 CO2 + 18 H2OGasoline liquid Gas Gas Gas
C + O2 CO2
Coal solid Gas Gas
2H2 + O2 H2O C + O2 CO2
N2 + O2 2NO
2H2O 2H2 + O2 2HgO 2Hg + O2 2NaCl 2Na + Cl2