Ch. 15 - Acids & BasesCh. 15 - Acids & Bases

Ch. 15-1 p. 542-549Ch. 15-2 p. 550-558

Ch. 15-1 p. 542-549Ch. 15-2 p. 550-558

PropertiesProperties

electrolytes electrolytes

turn litmus red

sour taste

react with metals to form H2 gas

slippery feel

turn litmus blue

bitter taste

ChemASAP

vinegar, milk, soda, apples, citrus fruits

ammonia, lye, antacid, baking soda

ArrheniusArrhenius - In aqueous solution… - In aqueous solution…

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

H

HH H H

H

ClClO O

–+

acid

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

Brønsted-LowryBrønsted-Lowry

HCl + H2O Cl– + H3O+

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

conjugate acidconjugate base

baseacid

Acids and bases come in pairs...Acids and bases come in pairs...

A A conjugate baseconjugate base is the is the remainder of the original acid, remainder of the original acid, after it donates it’s hydrogen after it donates it’s hydrogen ionion

A A conjugate acidconjugate acid is the particle is the particle formed when the original base formed when the original base gains a hydrogen iongains a hydrogen ion

H2O + HNO3 H3O+ + NO3–

CBCAAB

NH3 + H2O NH4+ + OH-

CA CBB A

F -

H2PO4-

H2O

HF

H3PO4

H3O+

Give the conjugate base for each of the following:

Br -

HSO4-

CO32-

HBr

H2SO4

HCO3-

Give the conjugate acid for each of the following:

Polyprotic AcidsPolyprotic Acids Some compounds have more than Some compounds have more than

1 ionizable hydrogen.1 ionizable hydrogen. HNOHNO3 3 nitric acid - monoprotic – 1 Hnitric acid - monoprotic – 1 H++

HH22SOSO44 sulfuric acid - diprotic - 2 H sulfuric acid - diprotic - 2 H++

HH33POPO44 phosphoric acid - triprotic - 3 phosphoric acid - triprotic - 3 HH++

Having more than one ionizable Having more than one ionizable hydrogen does not mean stronger hydrogen does not mean stronger acid!acid!

Not all the hydrogen in a Not all the hydrogen in a compound may be released compound may be released as ionsas ions

The hydrogen in a The hydrogen in a compound may be released compound may be released as ions when the hydrogen as ions when the hydrogen is joined to a very is joined to a very electronegative elementelectronegative element

LewisLewis•AcidsAcids are electron pair acceptors. •BasesBases are electron pair donors.

Lewis base

Lewis acid

Strengths of Acids and BasesStrengths of Acids and Bases

Strong acids completely ionize (100%) in Strong acids completely ionize (100%) in aqueous solutionsaqueous solutions

HCl + HHCl + H22O O HH33OO++ + Cl + Cl-- (100 % (100 %

ionsions))

Strong bases completely (100%) Strong bases completely (100%) dissociate into ions in aqueous solutions. dissociate into ions in aqueous solutions.

NaOH NaOH NaNa++ (aq) + OH (aq) + OH--(aq)(aq) (100 % ions)(100 % ions)

NHNH33, A Bronsted-Lowry Base, A Bronsted-Lowry Base

When NHWhen NH33 reacts with water, most of the reacts with water, most of the reactants remain dissolved as reactants remain dissolved as molecules, but a few NHmolecules, but a few NH33 reacts with reacts with water to form NHwater to form NH44

++ and hydroxide ion. and hydroxide ion.

NHNH33 + H + H22O O NH NH44++(aq) (aq) + +

OHOH-- (aq) (aq)

acceptoracceptor donor donor

++ ++

Strong and Weak Strong and Weak Acids and BasesAcids and Bases

Strong acidsStrong acids

HCl, HNOHCl, HNO3 3 ,, HH22SOSO44

Most other acids are weak.Most other acids are weak.

Strong basesStrong bases

NaOH, KOH, and Ca(OH)NaOH, KOH, and Ca(OH)22

Most other bases are weak.Most other bases are weak.

Learning Check

Identify each of the following as a

1) strong acid or base 2) weak acid

3) weak base

A. ___ HCl (aq)

B. ___ NH3(aq)

C. ___ NaOH (aq)

D. ___ H2CO3 (aq)

Solution

Identify each of the following as a

1) strong acid or base 2) weak acid

3) weak base

A. _1__ HCl (aq)

B. _3__ NH3(aq)

C. _1__ NaOH (aq)

D. _2__ H2CO3 (aq)

Antacids

Used to neutralize stomach acid (HCl)

Many contain one or more weak bases

Alka-Seltzer: NaHCO3, citric acid, and aspirin

Di-gel: CaCO3 and Mg(OH)2

Gelusil: Al(OH)3 and Mg(OH)2

Maalox: Al(OH)3 and Mg(OH)2

Mylanta: Al(OH)3 and Mg(OH)2

More Antacids

Milk of Magnesia: Mg(OH)2

Rolaids: AlNa(OH)2CO3

aluminum sodium dihydroxy carbonate

Tums: CaCO3

Tempo: CaCO3, Al(OH)3, Mg(OH)2