Chapter 4

Chapter 4Chapter 4

Reactions in Aqueous Reactions in Aqueous SolutionSolution

7.1 Predicting Whether a 7.1 Predicting Whether a Reaction Will Occur?Reaction Will Occur?

Driving ForcesDriving Forces Formation of solidFormation of solid Formation of waterFormation of water Transfer of electronsTransfer of electrons Formation of a gasFormation of a gas

7.2 Reactions in Which a 7.2 Reactions in Which a Solid Forms?Solid Forms?

Driving forcesDriving forces Precipitation – formation of solidPrecipitation – formation of solid

Ba(NOBa(NO33))22(aq) + K(aq) + K22CrOCrO44(aq) (aq) BaCrO BaCrO44(s) + (s) + 2KNO2KNO33(aq)(aq)

yellow sol.yellow sol. Colorless Yellow pptColorless Yellow ppt

7.2 Reactions in Which a 7.2 Reactions in Which a Solid Forms?Solid Forms?

Acid-Base Neutralization Reactions: Processes in which an acid reacts with a base to yield water plus a salt.

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

Some Ways That Some Ways That Chemical Reactions Chemical Reactions

OccurOccur Oxidation-Reduction (Redox) Oxidation-Reduction (Redox) Reactions: Processes in which one Reactions: Processes in which one or more electrons are transferred or more electrons are transferred between reactions partner (atoms, between reactions partner (atoms, molecules or ions)molecules or ions)

Mg(s) + 2HCl(aq) Mg(s) + 2HCl(aq) MgCl MgCl22(aq) + (aq) + HH22(g)(g)

Electrolytes in Aqueous Electrolytes in Aqueous SolutionSolution

Electrolytes:Electrolytes: substances which substances which dissolve in water to produce dissolve in water to produce conducting solution of ionsconducting solution of ions

HH22OO

NaCl(s) NaCl(s) Na Na++(aq) + Cl(aq) + Cl--(aq)(aq)

A solution of NaCl conducts electricity because of the movement of charged particles (ions).


Nonelectrolytes: substances which Nonelectrolytes: substances which do not produce ions in aqueous do not produce ions in aqueous solutionsolution

HH22OO

CC1212HH2222OO1111(s) (s) C C1212HH2222OO1111(aq)(aq)

A solution of C12H22O11 does not conduct electricity because it contains no charged particles (ions).


Strong electrolytes:Strong electrolytes: compounds compounds that dissociate to a large extent into that dissociate to a large extent into ions when dissolve in waterions when dissolve in water

HCl(aq) HCl(aq) H H++(aq) + Cl(aq) + Cl--(aq)(aq)

completely dissociatecompletely dissociate


Weak electrolytes:Weak electrolytes: compounds that compounds that dissociate to a small extent into ions dissociate to a small extent into ions when dissolve in waterwhen dissolve in water

H1+(aq) + CH3CO21-(aq)CH3CO2H(aq)


Strong Acids: hydrochloric acid, hydrobromic acid, hydroiodic acid, perchloric acid, nitric acid, sulfuric acid.

Predicting productPredicting product

Ba(NOBa(NO33))22(aq) + K(aq) + K22CrOCrO44(aq) (aq) yellow solidyellow solid

How to Decide What How to Decide What Products FormProducts Form

Write out all possible formula that Write out all possible formula that can be formedcan be formed

NONO33-- CrOCrO44

2-2-

KK++ KNOKNO33

BaBa2+2+ Ba(NOBa(NO33))22

Solubility of inorganic Solubility of inorganic compounds at 25Ccompounds at 25C

NONO33--, NO, NO22

--, ClO, ClO44--, ClO, ClO33

--, , MnOMnO44

--, Cr, Cr22OO77-2-2, CH, CH33COOCOO--

All nitrates are soluble. All nitrates are soluble.

NaNa++, K, K++ and NH4 and NH4++ All sodium, potassium and All sodium, potassium and ammonium salts are soluble. ammonium salts are soluble.

SOSO442-2- All sulfate salts are soluble except All sulfate salts are soluble except

BaBa2+2+, Sr, Sr2+2+ and Pb and Pb2+2+

ClCl--, Br, Br--, I, I-- and SCN and SCN-- All chlorides are soluble except for All chlorides are soluble except for AgCl, PbClAgCl, PbCl22 and Hg2 and Hg22+2+

COCO332-2-, PO, PO44

3-3-, SO, SO33-2-2, AsO, AsO333-, 3-,

AsOAsO33-3-3, BO, BO33

3-3-, SiO, SiO332-2-, C, C22OO44

2-2- and Fand F--

These salts are insoluble except for These salts are insoluble except for group IA cations and NHgroup IA cations and NH44

++ (FeC (FeC22OO44 is soluble) is soluble)

OO2- 2- and and --OHOH All oxides and hydroxides are All oxides and hydroxides are insoluble except Bainsoluble except Ba2+2+, Ca, Ca2+2+, Sr, Sr2+2+ and Group IA cations and Group IA cations

CrOCrO442-2- All salts are insoluble except NHAll salts are insoluble except NH44

++ , , MgMg2+2+, Ca, Ca2+2+, Sr, Sr2+2+, Cu, Cu2+2+ and group IA and group IA cations cations

SS2-2- All salts are insoluble except NHAll salts are insoluble except NH44++

and cations from group IA, IIA and and cations from group IA, IIA and AlAl3+3+

ExamplesExamples

Using solubility rules to predict the Using solubility rules to predict the product of Reactionsproduct of Reactions KNOKNO33(aq) + BaCl(aq) + BaCl22(g) (g) NaNa22S(aq) + Cu(NOS(aq) + Cu(NO33))22(aq) (aq) KOH(aq) + Fe(NOKOH(aq) + Fe(NO33))22(aq) (aq)

Identifying Precipitates in Identifying Precipitates in Reactions Where a Solid Reactions Where a Solid

FormsForms Step 1: Write the reactants as they Step 1: Write the reactants as they

actually exist before any reaction actually exist before any reaction occursoccurs

Step 2:Step 2: Consider the various solids Consider the various solids that could form.that could form.

Step 3: use solubility rules to decide Step 3: use solubility rules to decide whether a solid formswhether a solid forms

E.gE.g AgNOAgNO33(aq) + KCl(aq) (aq) + KCl(aq) white solidwhite solid

Describing Reactions in Describing Reactions in Aqueous SolutionsAqueous Solutions

Molecular equation:Molecular equation: shows overall shows overall reaction but not necessary the actual reaction but not necessary the actual forms of the reactants and products forms of the reactants and products in solutionin solution

AgNOAgNO33(aq) + NaCl(aq) (aq) + NaCl(aq) NaNO NaNO33(aq) (aq) + + AgCl(s)AgCl(s)


Complete ionic equation:Complete ionic equation: represents all reactants and represents all reactants and products that are strong electrolytes products that are strong electrolytes as ions. All reactants and products as ions. All reactants and products are included.are included.

AgAg++(aq) + (aq) + NONO33--(aq)(aq) + + NaNa++(aq)(aq) + Cl + Cl--

(aq) (aq) NaNa++(aq)(aq) + + NONO33--(aq) + (aq) + AgCl(s)AgCl(s)


The The net ionic equationnet ionic equation includes only includes only those components that undergoes a those components that undergoes a change. Spectator ions are not change. Spectator ions are not includedincluded

AgAg++(aq) + Cl(aq) + Cl--(aq) (aq) AgCl(s)AgCl(s)

Physical state must be included for all Physical state must be included for all equations or equations or No Credit.No Credit.

ExamplesExamples

For each of the following reactions, For each of the following reactions, write molecular equation, the write molecular equation, the complete ionic equation and the net complete ionic equation and the net ionic equationionic equation Cu(NOCu(NO33))22(aq) + Na(aq) + Na22COCO33(aq) (aq)

NHNH44NONO33(aq) + KCl(aq) (aq) + KCl(aq)

7.4 Reactions That Form 7.4 Reactions That Form Water: Acids and BasesWater: Acids and Bases

Arrhenius acids:Arrhenius acids: a substance that a substance that produces Hproduces H++ ions (protons) when it ions (protons) when it dissolved in waterdissolved in water Strong acids: strong electrolytesStrong acids: strong electrolytes Common strong acids: HCl, HBr, HI, Common strong acids: HCl, HBr, HI,

HH22SOSO44, HClO, HClO44, HNO, HNO33

Arrhenius AcidArrhenius Acid

Dissolve in waterDissolve in water

HA(aq) HA(aq) H H++(aq) + A(aq) + A--(aq)(aq)

HCl(aq) + HHCl(aq) + H22O O H H33OO++(aq) + Cl(aq) + Cl--(aq)(aq)


Arrhenius Bases:Arrhenius Bases: substance that substance that produces –OH ion (hydroxide ions) in produces –OH ion (hydroxide ions) in waterwater Strong bases: Strong electrolytesStrong bases: Strong electrolytes Common strong bases: KOH, LiOH, NaOH, Common strong bases: KOH, LiOH, NaOH,

Ba(OH)Ba(OH)22 and Sr(OH) and Sr(OH)22

MOH(aq) MOH(aq) M M++(aq) + (aq) + --OH(aq)OH(aq)


dissolved in Hdissolved in H22OO

NaOH(aq) -----------------NaOH(aq) ----------------- Na Na++(aq) + (aq) + --OH(aq)OH(aq)

Weak BaseWeak Base

NHNH33(aq) + H(aq) + H22O(l) O(l) NH NH44++(aq) + (aq) + --OH(aq)OH(aq)

Acids, Bases, and Acids, Bases, and Neutralization ReactionsNeutralization Reactions

Weak acids and weak bases are weak electrolytes.

Strong acids and strong bases are strong electrolytes.

Acids, Bases, and Acids, Bases, and Neutralization ReactionsNeutralization Reactions

These acid-base neutralization These acid-base neutralization reactions are double replacement reactions are double replacement reactions just like precipitionreactions just like precipition

MA + H2OHA + MOH

or

MA + HOHHA + MOH

WaterAcid Base Salt

Writing Equations for Acid-Writing Equations for Acid-Base ReactionsBase Reactions

HNOHNO33(aq) + Sr(OH)(aq) + Sr(OH)22(aq) (aq)

HH22SOSO44(aq) + NaOH(aq) (aq) + NaOH(aq)

Oxidation-Reduction Oxidation-Reduction (Redox) Reactions(Redox) Reactions

2Fe2O3(s)4Fe(s) + 3O2(g)Rusting of iron:an oxidation of Fe

4Fe(s) + 3CO2(g)2Fe2O3(s) + 3C(s) Manufacture of iron: a reduction of Fe

Oxidation-Reduction Oxidation-Reduction (Redox) Reactions(Redox) Reactions

Oxidation Number (state): a value Oxidation Number (state): a value which indicates whether an atom is which indicates whether an atom is neutral, electron-rich, or electron-neutral, electron-rich, or electron-poorpoor

Rules for Assigning Oxidation Numbers

An atom in its elemental state has an oxidation number of 0

Na Br2 SNe

Oxidation number 0

H2


A monatomic ion has an oxidation A monatomic ion has an oxidation number identical to its chargenumber identical to its charge

Na1+

+1

Ca2+

+2

Al3+

+3

Cl1-

-1

O2-

-2


An atom in a polyatomic ion or in a molecular compound usually has the same oxidation number it would have if it were a monatomic ion.

Hydrogen can be either +1 or -1.H O1-

-2+1

HH Ca

-1-1 +2


Oxygen usually has an oxidation number of -2.

OH O

-1+1 -1

HH O

+1+1 -2

H

+1


Halogens usually have an oxidation number of -1 except when bonding to oxygen.

H Cl

+1 -1

ClCl O

+1+1 -2


4. The sum of the oxidation numbers is 0 for a neutral compound and is equal to the net charge for a polyatomic ion.

Cr2O72-

-2x

x = +6

2(x) + 7(-2) = -2 (net charge)

H2SO3

x -2

x = +4

2(+1) + x + 3(-2) = 0 (net charge)

ExamplesExamples

Determine the oxidation for each Determine the oxidation for each atom in the following compoundsatom in the following compounds CdSCdS AlHAlH33

NHNH44++

NaNa22CrCr22OO77

Redox ReactionRedox Reaction Oxidizing Agent

Causes reduction Loses one or more electrons Undergoes oxidation Oxidation number of atom increases Reduction: Gaining e- (RIG)

Reducing Agent Causes oxidation Gains one or more electrons Undergoes reduction Oxidation number of atom decreases Oxidation: Losing e- (OIL)

Identifying Redox Identifying Redox ReactionsReactions

Reducing Agent

Oxidizing Agent

2Fe23O2(g)+4Fe(s) O3(s)

+30

oxidation

reduction

-20

3

Identifying Redox Identifying Redox ReactionsReactions

Reducing Agent

Oxidizing Agent

4Fe(s)C(s) +2Fe2O3 + 3 (g)(s) O2C

reduction

0+3

+40

oxidation

Redox Half ReactionRedox Half Reaction

Fe(s) + Cu Fe(s) + Cu 2+2+ (aq) (aq) Fe Fe 2+2+ (aq) (aq) + Cu(s) + Cu(s)

Oxidation: Fe(s) Oxidation: Fe(s) Fe Fe 2+2+ (aq) + (aq) + 2e-2e-

Reduction: Cu Reduction: Cu 2+2+ (aq) + (aq) + 2e-2e- Cu(s) Cu(s)

ExamplesExamples

For each of the following reactions, For each of the following reactions, show how electrons are gained and show how electrons are gained and lostlost 2 Al(s) + 3 I2 Al(s) + 3 I22(g) (g) 2 AlI 2 AlI33(s)(s)

2 Cs(s) + F2 Cs(s) + F22(g) (g) 2 CsF(s) 2 CsF(s)

2SO2SO22(g) + O(g) + O22(g) (g) 2SO 2SO33(g)(g)

The Activity Series of the The Activity Series of the ElementsElements

2Ag1+(aq) + Cu(s)2Ag(s) + Cu2+(g)

Cu2+(aq) + 2Ag(s)Cu(s) + 2Ag1+(g)

Which one of these reactions will occur?


The elements that are higher up in the table are more likely to be oxidized.

Thus, any element higher in the activity series will reduce the ion of any element lower in the activity series.


2Ag1+(aq) + Cu(s)2Ag(s) + Cu2+(g)

Cu2+(aq) + 2Ag(s)Cu(s) + 2Ag1+(g)

Which one of these reactions will occur?

ExamplesExamples

Mn(s) + AuClMn(s) + AuCl33(aq) (aq)

Fe(s) + Zn(NOFe(s) + Zn(NO33))2(2(aq) aq)

Cu(s) + HCl(aq) Cu(s) + HCl(aq)

Chapter 4

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