Acid-Base theories

Acid-Base theoriesAcid-Base theoriesAcid-Base theoriesAcid-Base theoriesAn IntroductionAn Introduction

Properties of acids and basesProperties of acids and bases

Acids:

Taste sour or tart

React with some metals to produce H2(g)

Turn litmus paper red

Can be strong (HCl) or weak (CH3COOH)

Acids:

Taste sour or tart

React with some metals to produce H2(g)

Turn litmus paper red

Can be strong (HCl) or weak (CH3COOH)


Common Acids:

HCl: hydrochloric acid

HNO3: nitric acid

H2SO4: sulfuric acid

H3PO4: phosphoric acid

CH3COOH: acetic (ethanoic) acid

H2CO3: carbonic acid

Common Acids:

HCl: hydrochloric acid

HNO3: nitric acid

H2SO4: sulfuric acid

H3PO4: phosphoric acid

CH3COOH: acetic (ethanoic) acid

H2CO3: carbonic acid


Bases:

Taste bitter

Feel slippery

Turn litmus paper blue

Can be strong (NaOH) or weak (NH3)

Bases:

Taste bitter

Feel slippery

Turn litmus paper blue

Can be strong (NaOH) or weak (NH3)


Common Bases:

KOH: potassium hydroxide

NaOH: sodium hydroxide

Ca(OH)2: calcium hydroxide

Mg(OH)2: magnesium hydroxide

Common Bases:

KOH: potassium hydroxide

NaOH: sodium hydroxide

Ca(OH)2: calcium hydroxide

Mg(OH)2: magnesium hydroxide

TheoriesTheories

Acid-Base theories try to explain the actions of acids and bases.

Acids and bases play such a very important role in general and biochemistry that we need a good theory to help us understand the reactions.

In addition, with a good theory, we should be able to predict the products of unknown but related reactions.

Acid-Base theories try to explain the actions of acids and bases.

Acids and bases play such a very important role in general and biochemistry that we need a good theory to help us understand the reactions.

In addition, with a good theory, we should be able to predict the products of unknown but related reactions.

TheoriesTheories

All theories deal with strong and weak acids and bases.

Strong acids and bases are fully dissociated in solution.

HCl(g) → H+(aq) + Cl-(aq)

NaOH(s) → Na+(aq) + OH-(aq)

The reactions go to completion.

There are no reactants present in the solution.

All theories deal with strong and weak acids and bases.

Strong acids and bases are fully dissociated in solution.

HCl(g) → H+(aq) + Cl-(aq)


The reactions go to completion.

There are no reactants present in the solution.

TheoriesTheories

Strong acids (these are all of them):

HCl hydrochloric acid

HBr hydrobromic acid

HI hydroiodic acid

HNO3 nitric acid

HClO3 chloric acid

H2SO4 sulfuric acid

Strong acids (these are all of them):

HCl hydrochloric acid

HBr hydrobromic acid

HI hydroiodic acid

HNO3 nitric acid

HClO3 chloric acid

H2SO4 sulfuric acid

TheoriesTheories

Strong bases:

all metal hydroxides, such as

NaOH sodium hydroxide

KOH potassium hydroxide

Ca(OH)2 calcium hydroxide

Strong bases:

all metal hydroxides, such as

NaOH sodium hydroxide

KOH potassium hydroxide

Ca(OH)2 calcium hydroxide

TheoriesTheories

Weak acids and bases are only partially dissociated.

There is an equilibrium when the rate of product formation equals the rate of reactant formation.

CH3COOH(aq) + H2O(l) ⇌ H3O+(aq) + CH3COO-

(aq)

NH3(aq) + H2O(l) ⇌ NH4+(aq) + OH-(aq)

Both reactants and products remain in solution.

Weak acids and bases are only partially dissociated.

There is an equilibrium when the rate of product formation equals the rate of reactant formation.

CH3COOH(aq) + H2O(l) ⇌ H3O+(aq) + CH3COO-

(aq)

NH3(aq) + H2O(l) ⇌ NH4+(aq) + OH-(aq)

Both reactants and products remain in solution.

TheoriesTheories

Weak acids:

any acid not a strong acid, such as

H3PO4 phosphoric acid

CH3COOH acetic acid

HF hydrofluoric acid

Weak acids:

any acid not a strong acid, such as

H3PO4 phosphoric acid

CH3COOH acetic acid

HF hydrofluoric acid

TheoriesTheories

Weak bases:

any base that is not a metal hydroxide, such as

NH3 ammonia

CH3NH2 methylamine

CH3CH2NH2 ethylamine

and other nitrogen containing organic compounds

Weak bases:

any base that is not a metal hydroxide, such as

NH3 ammonia

CH3NH2 methylamine

CH3CH2NH2 ethylamine

and other nitrogen containing organic compounds

Arrhenius acids and basesArrhenius acids and bases

Arrhenius acids are

H+ containing compounds

increase the H+ concentration in water

Typical reactions:

H-Cl(g) → H+(aq) + Cl-(aq)

H-Cl(g) + H2O(l)→ H3O+(aq) + Cl-(aq)

Arrhenius acids are

H+ containing compounds

increase the H+ concentration in water

Typical reactions:

H-Cl(g) → H+(aq) + Cl-(aq)

H-Cl(g) + H2O(l)→ H3O+(aq) + Cl-(aq)

hydronium ionhydronium ion

Arrhenius acids and basesArrhenius acids and bases

Arrhenius bases are

OH- containing compounds

increase the OH- concentration in water

Typical Reactions:


KOH(s) → K+(aq) + OH-(aq)

Arrhenius bases are

OH- containing compounds

increase the OH- concentration in water

Typical Reactions:


KOH(s) → K+(aq) + OH-(aq)

Brønsted-Lowry acids and basesBrønsted-Lowry acids and bases

Brønsted-Lowry acids are

H+ donors

HCl(g) + H2O(l) → Cl-(aq) + H3O+(aq)

Brønsted-Lowry bases are

H+ acceptors

NH3(g) + H2O(l) → NH4+(aq) + OH-(aq)

Brønsted-Lowry acids are

H+ donors


Brønsted-Lowry bases are

H+ acceptors

NH3(g) + H2O(l) → NH4+(aq) + OH-(aq)


Conjugate acids and bases:


In this reaction

HCl is the H+ donor (acid)

H2O is the H+ acceptor (base)



In this reaction

HCl is the H+ donor (acid)

H2O is the H+ acceptor (base)

(acid)(acid) (base)(base)




In the reverse reaction




H3O+ is the H+ donor (acid)

Cl- is the H+ acceptor (base)

H3O+ is the H+ donor (acid)

Cl- is the H+ acceptor (base)

(acid)(acid) (base)(base) (base)(base) (acid)(acid)






HCl is an acid

Cl- is a base

HCl and Cl- are conjugate acid and base.

HCl is an acid

Cl- is a base

HCl and Cl- are conjugate acid and base.







H3O+ is an acid

H2O is a base

H3O+ and H2O are conjugate acid and base.

H3O+ is an acid

H2O is a base

H3O+ and H2O are conjugate acid and base.




NH3(g) + H2O(l) → NH4+(aq) + OH-(aq)

In this reaction

H2O is the H+ donor (acid)

NH3 is the H+ acceptor (base)


NH3(g) + H2O(l) → NH4+(aq) + OH-(aq)

In this reaction

H2O is the H+ donor (acid)

NH3 is the H+ acceptor (base)

(base)(base) (acid)(acid)



NH3(g) + H2O(l) → NH4+(aq) + OH-(aq)



NH3(g) + H2O(l) → NH4+(aq) + OH-(aq)


NH4+ is the H+ donor (acid)

OH- is the H+ acceptor (base)

NH4+ is the H+ donor (acid)

OH- is the H+ acceptor (base)

(base)(base) (acid)(acid) (acid)(acid) (base)(base)



NH3(g) + H2O(l) → NH4+(aq) + OH-(aq)


NH3(g) + H2O(l) → NH4+(aq) + OH-(aq)

NH3 is a base

NH4+ is an acid

NH3 and NH4+ are conjugate acid and base.

NH3 is a base

NH4+ is an acid

NH3 and NH4+ are conjugate acid and base.




NH3(g) + H2O(l) → NH4+(aq) + OH-(aq)


NH3(g) + H2O(l) → NH4+(aq) + OH-(aq)

H2O is an acid

OH- is a base

H2O and OH- are conjugate acid and base.

H2O is an acid

OH- is a base

H2O and OH- are conjugate acid and base.



Notice that in the reaction


H2O acts as a base

and in the reaction

NH3(g) + H2O(l) → NH4+(aq) + OH-(aq)

H2O acts as an acid

Notice that in the reaction


H2O acts as a base

and in the reaction

NH3(g) + H2O(l) → NH4+(aq) + OH-(aq)

H2O acts as an acid


The behavior of water to act as a base or as an acid is called amphoterism.

Water is amphoteric.

Other species can also be amphoteric:

HSO4- (hydrogen sulfate ion)

HCO3- (hydrogen carbonate ion)

H2PO4- (dihydrogen phosphate ion)

The behavior of water to act as a base or as an acid is called amphoterism.

Water is amphoteric.

Other species can also be amphoteric:

HSO4- (hydrogen sulfate ion)

HCO3- (hydrogen carbonate ion)

H2PO4- (dihydrogen phosphate ion)

Lewis acids and basesLewis acids and bases

Lewis acid:

e- pair acceptor

H+ (the H is e- poor)

Lewis base:

e- pair donor

O−H- (the O is e- rich)

Lewis acid:

e- pair acceptor

H+ (the H is e- poor)

Lewis base:

e- pair donor

O−H- (the O is e- rich)::. .. .. .. .

Lewis acids and basesLewis acids and bases

Lewis acid/base reactions:

H+(aq) + H2O(l) → H3O+(aq)

H3O+ is called a Lewis acid/base adduct.

NH3(g) + H+(aq) → NH4+(aq)

Cl3B(g) + :NH3(g) → Cl3B−NH3(s)

Cl3B−NH3 is called a Lewis acid/base adduct.

Lewis acid/base reactions:

H+(aq) + H2O(l) → H3O+(aq)

H3O+ is called a Lewis acid/base adduct.

NH3(g) + H+(aq) → NH4+(aq)

Cl3B(g) + :NH3(g) → Cl3B−NH3(s)

Cl3B−NH3 is called a Lewis acid/base adduct.

acids/bases theoriesacids/bases theories

Type Acid Base

Arrhenius H+ producer OH- producer

Brønsted-Lowry H+ donor H+ acceptor

Lewis e- pair acceptor e- pair donor

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Acid-Base theories