Acids, Bases, & Salts Acids, Bases, & Salts

PropertiesProperties

Taste Sour. Can sting skin if open (cut).

React with metals to produce H2 gas.

Disassociate in water to produce ions that conduct electricity. (ELECTROLYTE)

Acids cause indicators to change color.Blue litmus paper turns red!

PropertiesProperties

Taste Bitter. Feel slippery to touch. Do not react with metals. Disassociate in water to produce ions that

conduct electricity. (ELECTROLYTE) Bases cause indicators to change color.

Red litmus paper turns blue!

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Neutralize each other in what is called a Neutralization Reaction.

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•Arrhenius AcidsArrhenius Acids form hydrogen ions (H+)

• HCl (hydrochloric acid)HCl (hydrochloric acid)

• HNOHNO33 (nitric acid) (nitric acid)

• HCHC22HH33OO22 (acetic acid) (acetic acid)

• HH22SOSO44 (sulfuric acid) (sulfuric acid)

• HH22COCO33 (carbonic acid) (carbonic acid)

• HH33POPO44 (phosphoric acid) (phosphoric acid)

DefinitionsDefinitions

•Arrhenius BasesArrhenius Bases form hydroxide ions (OH-)

• NaOH (sodium hydroxide)NaOH (sodium hydroxide)• KOH (potassium hydroxide)KOH (potassium hydroxide)

• Mg(OH)Mg(OH)22 (magnesium hydroxide) (magnesium hydroxide)

• Ca(OH)Ca(OH)22 (calcium hydroxide) (calcium hydroxide)

• Ba(OH)Ba(OH)22 (barium hydroxide) (barium hydroxide)

OH! It’s a base!

DefinitionsDefinitions

Always produce a salt and water

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

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

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DefinitionsDefinitions

Brønsted-LowryBrønsted-Lowry

HCl + H2O Cl– + H3O+

•AcidsAcids are hydrogen ion (H+) donors. •BasesBases are hydrogen ion (H+) acceptors.

baseacid

DefinitionsDefinitions

Types of Acids:Types of Acids:• Monoprotic AcidsMonoprotic Acids – have 1 proton to donate.

• Diprotic AcidsDiprotic Acids – have 2 protons to donate.

• Triprotic AcidsTriprotic Acids – have 3 protons to donate. HCl, HNO3, HF

H2SO4, H2CO3, H2S

H3PO4

Hydronium IonHydronium Ion

Produced when an acid dissociates in water and the water picks up the

hydrogen ion.

H3O+

H

HH H H

H

ClClO O

–+

Brønsted-Lowry Acids & BasesBrønsted-Lowry Acids & BasesBrønsted-Lowry Acids & BasesBrønsted-Lowry Acids & Bases

What part does water play?What part does water play?

H2O + HNO3 H3O+ + NO3–

AcidBase

What part does water play?What part does water play?

Water is amphoteric: can act as an can act as an

acid or a acid or a base.base.

NH3 + H2O NH4+ + OH-

Base Acid

Conjugate Acid – Base PairsConjugate Acid – Base Pairs

When a base gains a proton, it becomes its conjugate acid.When a base gains a proton, it becomes its conjugate acid. When an acid loses a proton, it becomes its conjugate base.When an acid loses a proton, it becomes its conjugate base.

HCl + H2O Cl– + H3O+

conjugate acidconjugate base

baseacid

Conjugate Acid – Base PairsConjugate Acid – Base Pairs

Pairs are joined together by the loss and gain of a proton.Pairs are joined together by the loss and gain of a proton. Acid & Base – Reactants side.Acid & Base – Reactants side. Conjugate Base & Conjugate Acid – Products side.Conjugate Base & Conjugate Acid – Products side.

NH3 + H2O NH4+ + OH-

acidbase conjugateacid

conjugatebase

Strength of Conjugate Acid-Base PairsStrength of Conjugate Acid-Base Pairs

The stronger the acid …

The weaker its conjugate base.

The weaker its conjugate acid.

The stronger the base …

Conjugate Acid – Base PairsConjugate Acid – Base Pairs

Determining Strengths of Acids and Bases

Determining Strengths of Acids and Bases

StrengthStrength

Strong Acids – Dissociate almost completely in water to produce HStrong Acids – Dissociate almost completely in water to produce H33OO++ ions ions Strong Bases – Strongly attract hydrogen ions in water, thus leaving OHStrong Bases – Strongly attract hydrogen ions in water, thus leaving OH--

- +

HCl

HNO3

H2SO4

NaOH

KOH

HBr

HI

HClO4

STRONG ACIDS STRONG

BASES

Ca(OH)2

CaO

StrengthStrength

Weak Acids – Dissociate slightly in water to produce HWeak Acids – Dissociate slightly in water to produce H33OO++ ions. Do not readily dissociate. ions. Do not readily dissociate. Weak Bases – react only partially with water to form OHWeak Bases – react only partially with water to form OH-- ions. ions.

NH3

H2NNH2

WEAK

ACIDS

WEAK BASES

CO32-2-

PO43-3-

- +

HF

CH3COOH

H3PO4

H2CO3

HCN

HCl + H2O H3O+ + Cl–

Strong Acid: SINGLE ARROW

DOUBLE ARROWWeak Acid:

HC2H3O2 + H2O H3O+ + C2H3O2–HC2H3O2 + H2O H3O+ + C2H3O2–

CaO Ca2+ + O2–

Strong Base: SINGLE ARROW

DOUBLE ARROWWeak Base:

CO32-

+ H2O

O2– + H2O 2OH–

HCO3- + OH–

Strong & WeakStrong & Weak

Acid Dissociation ConstantAcid Dissociation Constant

Ka = [H3O+][A-]

[HA]

Kais a measure of the strength of an acid.

HA(aq) + H2O (l)

The greater the Ka, the stronger the acid!

H3O+ (aq) + A–(aq)

Each ionization resultsin a different Ka value.

If the acid is diprotic or triprotic, the loss of each hydrogen

is a separate ionization.

Base Dissociation ConstantBase Dissociation Constant

Kb = [HB][OH-]

[B]

Kbis a measure of the strength of a base.

B(aq) + H2O(l) HB(aq) + OH–(aq)

The greater the Kb, the stronger the base!

Practice Problem #1Practice Problem #1

Acetic acid is a weak monoprotic acid. If the initial concentration of acetic acid is 0.200 M and the equilibrium concentration of H3O+ is 0.0019 M, calculate Ka for acetic acid.

Ka =[H3O+][A-]

[HA]

HA(aq) + H2O(l) H3O+(aq) + A–(aq)

Practice Problem #1Practice Problem #1

Ka =[H3O+][A-]

[HA]

HA(aq) + H2O(l) H3O+(aq) + A–(aq)

Use Stoichiometry!The reaction produces an A- ion

for every H3O+ ion.

[H3O+] = [A-]

Practice Problem #1Practice Problem #1

Ka =[H3O+][A-]

[HA]

HA(aq) + H2O(l) H3O+(aq) + A–(aq)

The equilibrium concentration of

HA equals its initial concentrationminus the amount

that ionizes.

[HA] = 0.200M – 0.0019M

[HA] = 0.1981M

Practice Problem #1Practice Problem #1

Ka =[H3O+][A-]

[HA]

HA(aq) + H2O(l) H3O+(aq) + A–(aq)

[H3O+] = [A-] = 0.0019M

[HA] = 0.1981M

=(0.0019M)(0.0019M)

(0.1981M)

= 1.8 x 10-5

Acid-Base Properties of SaltsAcid-Base Properties of Salts

Salts dissociate in water to form H3O+ or OH-

Knowing what type of acid and base formed the salt helps predict salt solution acid-base properties.

Acid-Base Properties of SaltsAcid-Base Properties of Salts

RULES:

Strong Acid + Strong Base Neutral Salt

Strong Acid + Weak Base

Weak Acid + Strong Base

Weak Acid + Weak Base

Acidic Salt

Basic Salt

Cannot predictvery easily

HCl + NaOH Neutral Salt

NaClSTRONGACID & BASE

NH3 + HClAcidic

Salt

NH4Cl

STRONGACID

WEAKBASE

NaOH + H2CO3

BasicSalt

Na2CO3

WEAKACID

STRONGBASE