Acid and Base

Ch 15 and 16

7-2

acids• 1. tastes sour.• 2. conducts an electric current.• 3. Causes certain dyes ( indicators) to change

color.• 4. Liberates hydrogen when it reacts with certain

metals.• 5. neutralizes basic solutions to form salts.

Bases

• 1. tastes bitter.• 2. conducts an electric current.• 3. causes certain dyes ( indicators) to change

color.• 4. feels slippery.• 5. neutralizes acid solution to form salts.

Definition of Acids and Bases

• An acid is a source of hydrogen ions (H+) or hydronium ions (H3O+ ) in solution.

HCl(aq) + H2O(l) H3O+ (aq) + Cl- (aq)

• A base is a source of hydroxide ions (OH-)

e.g. NaOH(s) Na+ (aq) + OH- (aq)

e.g. NH3 (aq) +H2O(l) NH4+ (aq) + OH-

(aq)

B. DefinitionsB. Definitions• ArrheniusArrhenius - In aqueous solution… - In aqueous solution…

HCl + H2O H3O+ + Cl–

– AcidsAcids form hydronium ions (H3O+)

H

HH H H

H

ClClO O

–+

acid

B. DefinitionsB. Definitions• 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

base

B. DefinitionsB. Definitions• Brønsted-LowryBrønsted-Lowry

HCl + H2O H3O+ + Cl-

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

conjugate base

conjugate acid

baseacid

Conjugate acid base pairs

• conjugate base: the species that remains after an acid has given up a proton

• conjugate acid: the species that is formed when a base gains a proton

NH3 + H2O NH4+ + OH-

conjugate base

conjugate acid

acidbase

• In the two examples water first acts as a base, then as an acid.

• Any species which can both accept and receive protons is called amphiprotic. (also known as amphoteric)

Br –

HSO4-

CO32-

HBr

H2SO4

HCO3-

• Give the conjugate acid for each of the following:

• List the conjugate acids for the following Bronsted bases

• OH -

• CO3 2-

• NO3-

• HCO3-

• CN -

H2O

HCO3-

HNO3

HCO3

HCN

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++

• List the conjugate bases for the following Bronsted acids

• H2SO4

• HPO42-

• HCO3-

• H3O+

• H2PO4-

HSO4-

PO43-

CO32-

H2O

HPO42-

Review 2: Name the acid, base, conjugate acid and base for each reaction.

CH3NH2 + H2O CH3NH3+ + OH -

H3PO4 + H2O H3O + + H2PO4 -

HC2H3O2 + H2O H3O + + C2H3O2 -

CH3NH3+ + H2PO4 - H3PO4 + CH3NH2

base

base

base

base

acid

acid

acid

acid

conjugate acid

conjugate acid

conjugate acid

conjugate acid

conjugate base

conjugate base

conjugate base

conjugate base

Review 2: Name the acid, base, conjugate acid and base for each reaction.

H2PO4- + OH- HPO4

2- + H2O

HCN + H2O CN- + H3O +

NH3 + H2O NH4 + + OH -

NO2- + HCO3 - CO3

2- + HNO2

acid

base

acid

acid

base

acid

base

base

conjugate base

conjugate base

conjugate acid

conjugate base

conjugate acid

conjugate acid

conjugate base

conjugate acid