Acid and Bases: An Introduction

Properties of Acids

1. Sour taste

2. Can produce H+ (hydrogen) ions (protons)

3. Change the color of litmus from blue to red

4. Reacts with metals such as Zn and Mg to produce H2 gas. Ba(s) + H2SO4 BaSO4(aq) + H2(g)

5. Reacts with carbonates (CO32-)to produce CO2

NaHCO3(s) + CH3COOH(aq) NaCH3COO(aq) + H2O(l) + CO2(g)

6. Acids conduct an electric current

Properties of Bases

1. Bitter or caustic taste2. A slippery, soapy feeling3. Can produce OH- (hydroxide) ions4. Ability to change litmus from red to blue5. Bases conduct an electric current6. Bases react with acids to produce a salt and water.

This is known as a neutralization reaction. HCl + NaOH NaCl + H2O HCl + Mg(OH)2 MgCl2 + H2O

acid base salt water

Ions in Solution

Acidic solutions contains more hydrogen (H+) ions than hydroxide ions (OH-) pH < 7

Basic solutions contains more hydroxide ions (OH-) than hydrogen ions pH > 7

Neutral solutions contain an equal concentration of hydrogen and hydroxide ions pH = 7

Question Time

What are the properties of acids? What are the properties of bases? What ion does an acid typically produce? What ion does a base typically produce? What is the OH- ion called? If there are more H+ ions than OH-, is the solution

acidic, basic, or neutral? What if there are an equal number of H+ and OH-

ions?

Three Definitions of Acids/Bases

Type Acid Base

Arrhenius H+ producer OH-producer

Bronsted-Lowry H+ donor H+ acceptor

Lewis Electron-pair acceptor

Electron-pair donor

Bronsted-Lowry Conjugate Acid/Base

HX(aq) + H2O(l) ⇆ H3O+(aq) + X-(aq)

acid base Conjugate Conjugate

Acid Base

Conjugate acid is the substance produced when a base accepts a hydrogen ion from an acid

Conjugate base is the substance that the acid donates a hydrogen ion to form a base

Bronsted-Lowry Conjugate Acid/Base

Conjugate acid-base pair consists of two substances related to each other by donating and accepting of a single hydrogen ion

NH3(aq) + H2O(l) NH4+ (aq) + OH-(aq)

base acid conjugate conjugate

acid base

Practice: Conjugate Acid and Conjugate Base

HCO3- + H2S ⇆ H2CO3 + HS-

H2PO4- + OH- ⇆ HPO4

2- + H2O

H2SO4 + NH3 ⇆ HSO4- + NH4

+

HC2H3O2 + H2O ⇆ H3O+ + C2H3O2-

Question Time

Name the three models of acids/bases. What is the Arrhenius model of acids/bases? What is the Bronsted-Lowry Model of Acid

bases? What is a conjugate acid and a conjugate base?

Question Time Identify the acid, base, conjugate acid, and conjugate base in

the Bronsted-Lowry reactions.

1. NH3 + H2O ⇆ NH4+ + OH-

2. H2O + CH3NH2 ⇆ OH- + CH3NH3+

3. HF + H2O ⇆ H3O+ + F-

4. HCOOH +CN- ⇆ HCOO- + HCN

5. NH4+ + CO3

2- ⇆ NH3 + HCO3-

Water in Acid/Base solutions

Water and other substances can act as both acids and bases and are said to be amphoteric

Hydronium ion = H3O+ = H+ (Remember H+ is a proton)

H2O(l) + H2O(l) ⇆ H3O+(aq) + OH-(aq)

Monoprotic and Polyprotic Acids

Monoprotic acid donates one hydrogen ion Polyprotic acid donates more than one

hydrogen ion

Question Time

What is a Lewis acid? What is a Lewis base? What is the H3O+ ion called? What is the shorthand way to write H3O+? What is amphoteric? Give an example.

Clicker Time

Which is not a property of acids?

A. Changes litmus paper red to blue

B. Sour taste

C. Conducts an electrical current

D. Reacts with metal to product H2 gas

Clicker Time

Which is not a property of bases?

A. Changes litmus paper red to blue

B. Sour taste

C. Feels slippery

D. Reacts with acids to product salt and water.

Clicker Time

What is an Arrhenius acid?

A. Hydrogen ion donor

B. Accepts an electron pair

C. Produces hydrogen ions

D. Produces a hydroxide

Clicker Time

What is a Bronsted-Lowry base?

A. Produces hydroxide ions

B. A hydrogen ion acceptor

C. An electron pair donor

D. Produces hydrogen ions

Clicker Time

What is a Lewis acid?

A. A hydrogen ion producer

B. A hydrogen ion donator

C. An electron pair acceptor

D. An electron pair donor

Clicker Time

HNO3 + H2O NO3- + H3O+

Which substance is the acid?

A. HNO3

B. H2O

C. NO3-

D. H3O+

Clicker Time

HNO3 + H2O NO3- + H3O+

Which substance is the conjugate base?

A. HNO3

B. H2O

C. NO3-

D. H3O+

Clicker Time

HCl + NH3 NH4+ + Cl-

Which substance is the base?

A. HCl

B. NH3

C. NH4+

D. Cl-

Clicker Time

HCl + NH3 NH4+ + Cl-

Which substance is the conjugate acid?

A. HCl

B. NH3

C. NH4+

D. Cl-