Intro to Acids

1
Intro to Acids Bases
2
Properties of Acids Bases

• Acids
• Taste sour
• Reacts with metals
• Turns litmus red
• Conducts electricity

• Base
• Taste bitter
• Slippery
• Turns litmus blue
• Conducts electricity

3
Ions in Solution

• Acidic solutions contain more H than OH-
• Basic solutions contain more OH- than H
• Neutral solutions contain equal amounts of H
  and OH-

4
Autoionization of Water

• H2O H2O ? H3O OH-
• Water is the usual solvent for acids and bases
• It produces equal numbers of H3O and OH-

5
Arrhenius Model of Acids Bases

• Acid a substance that contains H and ionized to
  produce H when dissolved in water.
• Base a substance that contains OH and ionizes to
  produce OH- when dissolved in water

6
Arrhenius Model of Acids Bases

• HCl ? H Cl-
• HCl contains H and ionizes to form H
• This could be an Arrhenius acid
• NaOH ? Na OH-
• NaOH contains OH and ionized to form OH-
• This could be considered an Arrhenius base

7
Arrhenius Model of Acids Bases

• Although the Arrhenius model is useful in
  describing many acids and bases, it does not
  describe them all
• For example NH3 contains no OH- ions, but it is a
  base
• A model to describe all bases is needed

8
Bronsted-Lowry Model

• Acid proton donor
• Base proton acceptor
• HX H20 ? H3O X-
• HX donates an H to the water molecule
• The water takes the H and is there for considered
  the base

9
Bronsted-Lowry Model

• Conjugate acid the species produced when a base
  accepts the H ion from the acid
• Conjugate base the species produced when the
  acid gives up its H

10
Conjugate Acids Conjugate Bases

• Identify the acid, base, conjugate acid, and
  conjugate base of the following reaction
• HX H20 ? H3O X-
• A B CA CB
• Every Bronsted-Lowry interaction involves
  conjugate acid base pairs

11
Conjugate Acids Conjugate Bases

• Identify the acid, base, conjugate acid, and
  conjugate base of the following reaction
• NH3 H20 ? NH4 OH-
• B A CA CB

12
Conjugate Acids Conjugate Bases

• What did you notice that was different about the
  previous two reactions?
• Water was an acid in one and a base in the other
• Amphoteric substance that can act as either an
  acid or a base

13
Conjugate Acids Conjugate Bases

• Identify the acid, base, conjugate acid, and
  conjugate base of the following reactions
• NH4 OH- ? NH3 H20
• A B CB CA
• HBr H2O ? H3O Br -
• A B CA CB

14
The pH Scale

• H is often expressed in very small numbers.
  Chemists needed an easier way to express H
  ions
• pH is a mathematical scale in which the
  concentration of hydronium ions in a solution is
  expressed as a number from 0 to 14.
• pH -logH

15
Interpreting the pH Scale

• pH of 7 is neutral. A pH less than 7 is acidic,
  and a pH greater than 7 is basic.

pH pOH 14
16
Acid Strength

• The strength of an acid or a base tells you the
  degree of ionization
• Strong acids bases break down into many ions
• Weak acids bases break down into just a few ions

17
Neutralization Reactions

• Neutralization reactions acid base ? a salt
  water
• Neutralization reactions are just a special type
  of double replacement reactions

18
Neutralization Reactions

• Write the equations for the following
  neutralization reactions
• Acetic acid and ammonium hydroxide
• HCH3COO NH4OH ? HOH NH4CH3COO
• Nitric acid and cesium hydroxide
• HNO3 CsOH ? HOH CsNO3