Review: Arrhenius Definition of Review: Arrhenius Definition of Acids and BasesAcids and Bases

Acids produce HAcids produce H++ in aqueous (water) solutions in aqueous (water) solutions waterwater

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

Bases produce OHBases produce OH-- in aqueous (water) solutions in aqueous (water) solutions

waterwater

NaOHNaOH Na Na+ + (aq) + OH(aq) + OH- - (aq)(aq)

The BrThe Brøønsted-Lowry Definition nsted-Lowry Definition of Acids and Basesof Acids and Bases

Acid:Acid: PROTON DONOR PROTON DONOR

can donate Hcan donate H++ ions. ions.

Base:Base: PROTON ACCEPTORPROTON ACCEPTOR

acceptsaccepts HH++ ions. ions.

Broader Definition than ArrheniusBroader Definition than Arrhenius

HH++ Transfer Transfer

Acid/base reactions involve Acid/base reactions involve ““proton transferproton transfer”.”.

The reaction need not occur in water.The reaction need not occur in water.

HH++ leaves one compound and is leaves one compound and is transferred to another.transferred to another.

Ex: Ex: NHNH33 + H + H22O O NHNH44++ + +

OHOH--

BaseBase AcidAcid

Follow the HFollow the H++

Conjugate acid/base pairs:Conjugate acid/base pairs: formulas differformulas differ

by only a hydrogen ion, Hby only a hydrogen ion, H++..

The acid on one side becomes the base onThe acid on one side becomes the base on

the other side and vice versa.the other side and vice versa.

Ex: Ex:

HCl + HHCl + H22O O HH33OO++ + Cl + Cl--

AcidAcid Base Base AcidAcid Base Base

Conjugate acidConjugate acid

contains onecontains one

more Hmore H++ in its in its

formulaformula

Label the Conjugate Acids and Label the Conjugate Acids and Bases in Each ReactionBases in Each Reaction

Amphoteric/Amphiprotic Substances:Amphoteric/Amphiprotic Substances:

Can act as either an acid or a base.Can act as either an acid or a base.

Must have an “H” in formula (to donate)Must have an “H” in formula (to donate)

Must have a free eMust have a free e-- pair (to accept a H pair (to accept a H++))

Water is amphotericWater is amphoteric

It can donate an HIt can donate an H++ or accept an Hor accept an H++

It depends on what it It depends on what it is combined with.is combined with.

Water Water donates Hdonates H++

to NHto NH33 forming the hydroxide ion (OH forming the hydroxide ion (OH--). ).

Water Water acceptsaccepts HH++

from HCl forming the hydronium ion (Hfrom HCl forming the hydronium ion (H33OO++).).

When it can go either way…Amphoteric (amphiprotic) substances

HCO3-

H2CO3 CO3-2

+ H+ - H+

Acting like a base

Acting like an acid

accepts H+ donates H+

Let’s PracticeLet’s Practice

What is the Brønsted-Lowry definition of an What is the Brønsted-Lowry definition of an acid? acid?

1)1) A substance that donates protons. A substance that donates protons.

2)2) A substance that accepts protons. A substance that accepts protons.

3)3) A substance that dissolves in water to form ions. A substance that dissolves in water to form ions.

4)4) A substance that dissolves in water to form ions.A substance that dissolves in water to form ions.

If HIf H33OO++ is an acid according to the is an acid according to the

Brønsted-Lowry theory, what is the Brønsted-Lowry theory, what is the conjugate base of this acid? conjugate base of this acid?

1)1) HH44OO+2+2 (aq)(aq)

2)2) HH++ (aq)(aq)

3)3) HH22O O (l)(l)

4)4) OHOH-- (aq)(aq)

According to one acid-base theory, water According to one acid-base theory, water acts as an acid when an Hacts as an acid when an H22O moleculeO molecule

(1) accepts an H+ (1) accepts an H+ 

(2) accepts an H-(2) accepts an H-

(3) donates an H+ (3) donates an H+ 

(4) donates an H- (4) donates an H-

One acid-base theory defines a base as One acid-base theory defines a base as anan

(1) H+ donor        (1) H+ donor       

(2) H donor(2) H donor

(3) H+ acceptor   (3) H+ acceptor  

(4) H acceptor (4) H acceptor

What is the conjugate base of HWhat is the conjugate base of H22POPO44--

1)1) HH33O+ O+ (aq)(aq)

2)2) HH33POPO44 (aq)(aq)

3)3) HPOHPO44-2-2 (aq)(aq)

4)4) POPO44-3-3 (aq)(aq)

Online tutorial on Bronsted/LowryOnline tutorial on Bronsted/Lowryhttp://www.sophia.org/acids-and-bases-defhttp://www.sophia.org/acids-and-bases-def

initions-bronsted-lowry/acids-and-bases-dinitions-bronsted-lowry/acids-and-bases-definitions-bronsted-lowry-tutorialefinitions-bronsted-lowry-tutorial

Dilution

water (solvent) solute

concentrated, Minitial

diluted, Mfinal

adding water lowers the solute concentration

moles of solute remain constant

Vinitial

Vfinal

molesinitial = molesfinal

Mfinal x Vfinal = Minitial x Vinitial

Acid/Base Summary FilmsAcid/Base Summary Films The Proton in Chemistry The Proton in Chemistry

http://www.learner.org/vod/vod_window.html?pid=808http://www.learner.org/vod/vod_window.html?pid=808

Acid and Base Tutorial:Acid and Base Tutorial:http://http://www.youtube.com/watch?vwww.youtube.com/watch?v=MzK3bDkzXq4&safe=active=MzK3bDkzXq4&safe=active

Acid Base QuizAcid Base Quizhttp://www.sciencegeek.net/Chemistry/taters/Unit6AcidsBases.htmhttp://www.sciencegeek.net/Chemistry/taters/Unit6AcidsBases.htm

Acid Bases Hydrogen Transfer (Neutralization)Acid Bases Hydrogen Transfer (Neutralization)http://preparatorychemistry.com/neutralization_flash.htmhttp://preparatorychemistry.com/neutralization_flash.htm