1 Net ionic equations. 2 REDOX REACTIONS EXCHANGEAcid-BaseReactionsEXCHANGEGas-FormingReactions...

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Net ionic equationsNet ionic equations

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REDOX REDOX REACTIONSREACTIONS

REDOX REDOX REACTIONSREACTIONS

EXCHANGEEXCHANGEAcid-BaseAcid-BaseReactionsReactions

EXCHANGEEXCHANGEGas-FormingGas-FormingReactionsReactions

EXCHANGEEXCHANGE:: Precipitation Reactions Precipitation Reactions

REACTIONSREACTIONS

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TerminologyTerminologyTerminologyTerminology

In solution we need to define the In solution we need to define the --

• SOLVENTSOLVENT

the component whose the component whose physical state is physical state is preserved when preserved when solution formssolution forms

• SOLUTESOLUTE

the other solution componentthe other solution component

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IONIC COMPOUNDSIONIC COMPOUNDSCompounds in Aqueous SolutionCompounds in Aqueous Solution

Many reactions involve ionic compounds, Many reactions involve ionic compounds,

especially reactions in water — especially reactions in water — aqueous aqueous solutions.solutions.

KMnOKMnO44 in water in water KK++(aq) + MnO(aq) + MnO44--(aq)(aq)

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An Ionic An Ionic Compound, Compound,

CuClCuCl22, in , in WaterWater

CCR, page 149CCR, page 149

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How do we know ions are How do we know ions are present in aqueous present in aqueous solutions?solutions?

The solutions The solutions conduct conduct electricity!electricity!

They are called They are called ELECTROLYTESELECTROLYTES

HCl, MgClHCl, MgCl22, and NaCl are , and NaCl are strong strong electrolyteselectrolytes. . They They dissociate completely (or dissociate completely (or nearly so) into ions.nearly so) into ions.

Aqueous Aqueous SolutionsSolutions

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HCl, MgClHCl, MgCl22, and NaCl are , and NaCl are strong strong electrolyteselectrolytes. . They dissociate They dissociate completely (or nearly so) into ions.completely (or nearly so) into ions.

Aqueous Aqueous SolutionsSolutions

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An acid -------> HAn acid -------> H++ in water in waterAn acid -------> HAn acid -------> H++ in water in water

ACIDSACIDSACIDSACIDS

Some Some strongstrong acids areacids are

HClHCl hydrochlorichydrochloric

HH22SOSO44 sulfuricsulfuric

HClOHClO44 perchloricperchloric

HNOHNO33 nitricnitricHNOHNO33

Basic Chemistry Copyright © 2011 Pearson Education, Inc.9

Strong acids• make up six of all the acids • have weak conjugate bases

Strong Acids


Strong Bases

Strong bases • are formed from metals of

Groups 1A (1) and 2A (2) • include LiOH, NaOH, KOH,

and Ba(OH)2

• dissociate 100% in water

KOH(s) K+(aq) + OH−(aq)

Bases in household products are used to remove grease and to open drains.

11Aqueous Aqueous SolutionsSolutions

Acetic acid ionizes only to a small extent, so Acetic acid ionizes only to a small extent, so it is a it is a weak electrolyte.weak electrolyte.CHCH33COCO22H(aq)H(aq) ---> ---> CHCH33COCO22

--(aq) + H(aq) + H++(aq)(aq)

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Weak AcidsWeak AcidsWeak AcidsWeak AcidsWEAK ACIDS = weak WEAK ACIDS = weak

electrolyteselectrolytes

CHCH33COCO22HH

acetic acidacetic acid

HH22COCO33 carbonic acidcarbonic acid

HH33POPO44 phosphoric phosphoric acidacid

HFHF

hydrofluoric acidhydrofluoric acid

Acetic acid


Weak acids• make up most of the acids• have strong conjugate bases

Weak Acids


Weak Bases

Weak bases • are poor acceptors of protons• dissociate only slightly in water• produce only a few ions in water• are used in household products

such as cleaners

NH3(g) + H2O(l) NH4+(aq) + OH−(aq)

15AqueouAqueou

s s SolutionSolution

ssAcetic acid ionizes only to a small Acetic acid ionizes only to a small extent, so it is a extent, so it is a weak weak electrolyte.electrolyte.

CHCH33COCO22H(aq)H(aq) ---> ---> CHCH33COCO22--(aq) + (aq) +

HH++(aq)(aq)

16Aqueous Aqueous SolutionsSolutions

Some compounds Some compounds dissolve in water but do dissolve in water but do not conduct electricity. not conduct electricity. They are called They are called nonelectrolytes.nonelectrolytes.

Examples include:Examples include:sugarsugarethanolethanolethylene glycolethylene glycol

Examples include:Examples include:sugarsugarethanolethanolethylene glycolethylene glycol


Learning Check

Identify each of the following as a strong or weak acid or base:

A. HBr

B. HNO2

C. NaOH

D. H2SO4

E. Cu(OH)2

strong acid

weak acid

strong basestrong acid

weak base


Learning Check

A. Identify the stronger acid in each pair.

1. HNO2 or H2S

2. HCO3- or HBr

3. H3PO4 or H3O+

B. Identify the stronger base in each pair.

1. NO3- or F-

2. CO32- or NO2

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3. OH- or H2O

Basic Chemistry Copyright © 2011 Pearson Education, Inc.

Acid-Base ReactionsAcid-Base Reactions The “driving force” = formation of water.The “driving force” = formation of water.

NaOH (NaOH (aqaq) + HCl () + HCl (aqaq) ) ’’

NaCl (NaCl (aqaq) + H) + H22O (l)O (l)

Net ionic equationNet ionic equation

OHOH- - ((aqaq) + H) + H+ + ((aqaq) ) ’’ H H22O (l)O (l)

This applies to ALL reactions This applies to ALL reactions

of of STRONGSTRONG acids and bases. acids and bases.


Gas-Forming Gas-Forming ReactionsReactions

The chemistry of The chemistry of metal carbonatesmetal carbonates..

COCO22 and water and water ’’ H H22COCO33

HH22COCO3 3 ((aqaq) + Ca) + Ca2+2+ ’’

2 H2 H++((aqaq) + CaCO) + CaCO3 3 (s) (limestone)(s) (limestone)

Adding acid reverses this reaction.Adding acid reverses this reaction.

MCOMCO33 + acid + acid ’’ CO CO22 + salt + salt

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Water Solubility of Ionic Water Solubility of Ionic CompoundsCompounds

Common minerals are often formed with Common minerals are often formed with anions that lead to insolubility:anions that lead to insolubility:

sulfidesulfide fluoridefluoride

carbonatecarbonate oxideoxide

Azurite, a copper carbonate

Iron pyrite, a sulfideOrpiment, arsenic sulfide

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Precipitation Precipitation ReactionsReactions

Precipitation Precipitation ReactionsReactions

The “driving force” is the formation of an The “driving force” is the formation of an insoluble compound — a insoluble compound — a precipitateprecipitate..

Pb(NOPb(NO33))2 2 ((aqaq) + 2 KI () + 2 KI (aqaq) ) ’’

2 KNO2 KNO3 3 ((aqaq) + PbI) + PbI2 2 ((ss))

Net ionic equationNet ionic equation

PbPb2+ 2+ ((aqaq) + 2 I) + 2 I- - ((aqaq) ) ’’ PbI PbI2 2 ((ss))

28Net Ionic Net Ionic EquationsEquationsNet Ionic Net Ionic EquationsEquations

Mg(s) + 2 HCl(Mg(s) + 2 HCl(aqaq) --> H) --> H22(g) + MgCl(g) + MgCl22((aqaq))

We really should writeWe really should write

Mg(s) + 2 HMg(s) + 2 H++((aqaq) + 2 Cl) + 2 Cl--((aqaq) --->) --->

HH22(g) + Mg(g) + Mg2+2+((aqaq) + 2 Cl) + 2 Cl--((aqaq))

The two ClThe two Cl-- ions are ions are SPECTATOR IONSSPECTATOR IONS — — they do not participate.they do not participate.

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Li+(aq) + Na+(aq) + OH-(aq) + CrO4-(aq) ---> Li+(aq) + Na+(aq) + OH-(aq) + CrO4

-(aq) Li+(aq) + Na+(aq) + OH-(aq) + CrO4-(aq) ---> Li+(aq) + Na+(aq) + OH-(aq) + CrO4

-(aq)

Cr3+(aq) + Na+(aq) + NO3-(aq) + Br-(aq) ---> Cr3+(aq) + Na+(aq) + NO3

-(aq) + Br-(aq) Cr3+(aq) + Na+(aq) + NO3-(aq) + Br-(aq) ---> Cr3+(aq) + Na+(aq) + NO3

-(aq) + Br-(aq)

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If one ion from the If one ion from the “Soluble Compd.” list is “Soluble Compd.” list is present in a compound, present in a compound, the compound is water the compound is water

soluble.soluble.

Water Solubility of Ionic Water Solubility of Ionic CompoundsCompounds

Screen 5.4 & Figure 5.1

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