Acid Definitions

Arrhenius Acids and BasesAcids release hydrogen ions in water.Bases release hydroxide ions in water.

An acid is a substance that produces hydronium ions, H3O+, when dissolved in water.

Lewis DefinitionsA Lewis acid is a substance than can accept (and share) an electron pair.A Lewis base is a substance than can donate (and share) an electron pair.

Lewis Acid

Brønsted-Lowry DefinitionsA Brønsted-Lowry acid is a proton donor; it donates a hydrogen ion, H+.A Brønsted-Lowry base is a proton acceptor; it accepts a hydrogen ion, H+.

Brønsted-Lowry

Arrheniusacids

Acid Definitions

Acid Definitions

Lewis acids

Brønsted-Lowry

Arrheniusacids

The Arrhenius model of acidsand bases was broadened bythe Brønsted-Lowry model.

The Lewis acid-base model isthe most general in scope.

The Lewis definition of an acidincludes any substance thatis an electron pair acceptor;a Lewis base is any substancethat can act as an electron pair donor.

Ralph A. Burns, Fundamentals of Chemistry 1999, page 483

Lewis acids

Brønsted-Lowry

Arrheniusacids

The Arrhenius model of acidsand bases was broadened bythe Brønsted-Lowry model.

The Lewis acid-base model isthe most general in scope.

The Lewis definition of an acidincludes any substance thatis an electron pair acceptor;a Lewis base is any substancethat can act as an electron pair donor.

Ralph A. Burns, Fundamentals of Chemistry 1999, page 483

Acid Definitions

Acid – Base Systems

Type Acid Base

Arrhenius H+ or H3O + producer

OH - producer

Brønsted-

Lowry

Proton (H +) donor

Proton (H +) acceptor

Lewis Electron-pair acceptor

Electron-pair donor

Arrhenius Acid

1+

+ +

hydronium ion

H3O+

1-

chloride ion

Cl-

water

H2O

hydrogen chloride

HCl

(an Arrhenius acid)

Any substance that releases H+ ions as the only positive ion in the aqueous solution.

DefinitionsDefinitions

ArrheniusArrhenius - In aqueous solution… - In aqueous solution…

HCl + H2O H3O+ + Cl– •AcidsAcids form hydronium ions (H3O+)

H

HH H H

H

ClClO O

–+

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ArrheniusArrhenius - In aqueous solution… - In aqueous solution…

•BasesBases form hydroxide ions (OH-)

NH3 + H2O NH4+ + OH-

H

H

HH H

H

N NO O–+

H

H

H H

baseCourtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Arrhenius Bases and Their Properties

According to the definition of Arrhenius a:

BaseBase - "a substance whose water solution yields...

Are NaOH and NH3 considered to be Arrhenius bases?

1) Bases are electroytes

Dissociation equation for NH3

NH3(g) + H2O(l) NH41+(aq) + OH1-(aq)

Dissociation equation for NaOH

NaOH(s) Na1+(aq) + OH1-(aq)

2) Bases cause indicatorsindicators to turn a characteristic color

3) Bases neutralize acidsNaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)

YES

4) Water solutions of bases tasted bitter and feel slippery.

hydroxide ions (OH-) as the only negative ions."

Neutralization

NeutralizationNeutralization is a chemical reaction between an acid and a base to produce a salt (an ionic compound) and water.

NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)base acid salt water

Some neutralization reactions:

H2SO4(aq) + NaOH(aq) Na2SO4 + HOH

sulfuric acid sodium hydroxide sodium sulfate water

HC2H3O2(aq) + Ca(OH)2(aq) Ca(C2H3O2)2 + HOH

acetic acid calcium hydroxide calcium acetate water

2 2

2 2

NeutralizationNeutralization

ACID + BASE ACID + BASE SALT + WATER SALT + WATER

HCl + NaOH HCl + NaOH NaCl + H NaCl + H22OO

HCHC22HH33OO22 + NaOH + NaOH NaC NaC22HH33OO22 + H + H22OO

• Salts can be neutral, acidic, or basic.

• Neutralization does not mean pH = 7.

weak

strong strong

strong

neutral

basic

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

ACID + BASE ACID + BASE SALT + WATER SALT + WATER

HCl + NaOH HCl + NaOH NaCl + H NaCl + H22OO

HCHC22HH33OO22 + NaOH + NaOH NaC NaC22HH33OO22 + H + H22OO

• Salts can be neutral, acidic, or basic.

• Neutralization does not mean pH = 7.

weak

strong strong

strong

neutral

basic


Salts

SaltsSalts - Ionic compounds containing a positive ion other than the hydrogen ion and a negative ion other than the hydroxide ion.

i.e., a metal and a non-metal

Under what conditions do salts conduct current?

NaCl(s) + H2O(l) Na1+(aq) + Cl1-(aq)

Formulas and names of common salts

SALT FORMULA Common Name

sodium chloride NaCl (table) salt

sodium nitrate NaNO3 Chile saltpeter

sodium bicarbonate NaHCO3 baking soda

potassium carbonate K2CO3 potash

ammonium chloride NH4Cl sal ammoniac

NaCl

Salt Formation

NaOH HCl

strongbase

strongacid

salt of a strong base and a strong acidNaCl

NaOH HC2H3O2

strongbase

weakacid

salt of a strong base and a weak acidNaC2H3O2

Note: that in each case H-OH (water) is formed

NaOH + HCl NaCl + H2O

NaOH + HC2H3O2 NaC2H3O2 + H2O

Salt Formation

NH3H2SO4

weakbase

strongacid

salt of a weak base and a strong acid(NH4) 2 SO4

NH3HC2H3O2

weakbase

weakacid

salt of a weak base and a weak acidNH4 C2H3O2

Note: that in each case H-OH (water) is also formed

NH4OH H2SO4

NH4OH + H2SO4 (NH4)2SO4 + H2O

NH4OH + HC2H3O2 NH4C2H3O2 + H2O

NH3H2SO4

weakbase

strongacid

salt of a weak base and a strong acid(NH4) 2 SO4

NH4OH H2SO4

ammonium ion

NH4+

hydroxide ion

OH-

1+ 1-

NH4+ OH-

1+ 1-

sulfuric acid

(NH4)2SO4

HOH

1+

HOH

1+

sulfate ion

2 NH4OH + H2SO4 (NH4)2SO4 + 2 HOH

waterammonium sulfate

2-

H2SO4

2 NH4OH + H2SO4 (NH4)2SO4 + 2 H2O

phosphoric acid ammonium hydroxide ammonium phosphate

Reactions that produce salt acid + base salt + water

H3PO4 NH4OH (NH4)3PO4 H2O

nitric acid magnesium hydroxide magnesium nitrateHNO3 Mg(OH)2 Mg(NO3)2 H2O

carbonic acid potassium hydroxide potassium carbonateH2CO3 KOH K2CO3 H2O

acetic acid aluminum hydroxide aluminum acetateHC2H3O2 Al(OH)3 Al(C2H3O2)3 H2O

perchloric acid barium hydroxide barium perchlorateHClO4 Ba(OH)2 Ba(ClO4)2 H2O

+ +and yields and water

Brønsted-Lowry Acids and Bases

1+

+

hydronium ion

H3O+

1-

chloride ion

Cl-

(base)

H2O

(acid)

HCl

+ -

Acid = any substance that donates a proton.

Base = any substance that accepts a proton.


(acid)

H2O

(base)

NH3

+-1+

+

ammonium ion

NH4+

1-

hydroxide ion

OH-


1+

+

ammonium ion

NH4+

1-

hydroxide ion

OH-

(acid)

H2O

(base)

NH3

+-


Brønsted-LowryBrønsted-Lowry

HCl + H2O Cl– + H3O+

•AcidsAcids are proton (H+) donors. •BasesBases are proton (H+) acceptors.

conjugate acidconjugate base

baseacid



H2O + HNO3 H3O+ + NO3–

CBCAAB


H

H

OH O

O

ON

Base Acid


Amphoteric - can be an acid or a base. - can be an acid or a base.

NH3 + H2O NH4+ + OH-

CA CBB A


H

H

OH

N

Base Acid

H

H


F -

H2PO4-

H2O

HF

H3PO4

H3O+

Give the conjugate base for each of the following:

Polyprotic - an acid with more than one H - an acid with more than one H++



Br -

HSO4-

CO32-

HBr

H2SO4

HCO3-

Give the conjugate acid for each of the following:



LewisLewis• AcidsAcids are electron pair acceptors.

• BasesBases are electron pair donors.

Lewis base

Lewis acid


Acid Definitions

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