know the Arrhenius definition and the BronsteadLowry definition of an acid and a base'

1
Acids and Bases Goals
At the end of this chapter you should

• know the Arrhenius definition and the
  Bronstead-Lowry definition of an acid and a base.
• know how to name common acids and bases.
• know how acids and bases are classified as
  strong or weak.
• know how to describe the ionization of water
  and the concept of the ion product of water.
• know the pH scale and how to calculate pH from
  the H and H and OH- from pH
• know how acids react with Bases.
• know the concept of a buffer and how buffers
  help maintain biological pH.

2
Acids and Bases of the Arrhenius type

• Arrhenius acids
• produce H ions in water.
• HCl(g) H(aq) Cl- (aq)
• are electrolytes.
• have a sour taste.
• turn litmus red.
• neutralize bases.
• Arrhenius bases
• produce OH- ions in water.
• taste bitter or chalky.
• are electrolytes.
• feel soapy and slippery.
• neutralize acids.

H2O
3
Acids and Bases Naming

• Acids with H and a nonmetal are named with the
  prefix hydro and end with ic acid.
• HCl hydrochloric acid
• Acids with H and a polyatomic ion are named by
  changing the end of the name of the polyatomic
  ion from ate to ic acid or ite to ous acid.
• ClO3- chlorate HClO3 chloric acid
• ClO2- chlorite HClO2 chlorous acid
• Bases with OH- ions are named as the hydroxide
  of the metal in the formula.
• NaOH-sodium hydroxide KOH-potassium hydroxide
• Ba(OH)2-barium hydroxid

4
Acids and Bases of the Bronsted-Lowry type

• According to the BrØnsted-Lowry theory,
• acids donate a proton (H).
• bases accept a proton (H).

5
Acids and Bases strength of acids and bases

• A strong acid completely ionizes (100) in
  aqueous solutions.
• HCl(g) H2O(l) H3O
  (aq) Cl- (aq)
• A weak acid dissociates only slightly in water to
  form a few ions in aqueous solutions.
  
• CH3COOH(aq) H2O(l)
  H3O(aq) CH3COO- (aq)

In an HCl solution, the strong acid HCl
dissociates 100. A solution of the weak acid
CH3COOH contains mostly molecules and a few ions.
6
Acids and Bases strength of acids and bases

• Strong acids
• make up six of all the acids.

7
Acids and Bases strength of acids and bases

• Weak acids
• make up most of the acids.

8
Acids and Bases strength of acids and bases

• Strong bases
• are formed from metals of Groups 1A (1) and 2A
  (2).
• include LiOH, NaOH, KOH, and Ca(OH)2.
• dissociate completely in water.
• KOH(s) K(aq) OH-(aq)
• Weak bases
• are most other bases.
• dissociate only slightly in water.
• form only a few ions in water.
• NH3(g) H2O(l) NH4(aq) OH-(aq)

9
Acids and Bases water as an acid and a base

• In water,
• H is transferred from one H2O molecule to
  another.
• one water molecule acts as an acid, while another
  acts as a base.
• H2O H2O H3O
  OH-
• water water
  hydronium hydroxide
• 
  ion () ion (-)
• In pure water,
• the ionization of water molecules produces small,
  but equal quantities of H3O and OH- ions.
• molar concentrations are indicated in brackets as
  H3O and OH-.
• H3O 1.0 x 10-7 M
• OH- 1.0 x 10-7 M

10
Acids and Bases ionization of water

• The ion product constant, Kw, for water
• is the product of the concentrations of the
  hydronium and hydroxide ions.
• Kw H3O OH-
• can be obtained from the concentrations in pure
  water.
• Kw H3O OH-
• Kw 1.0 x 10- 7 M x 1.0 x 10- 7 M
  
• 1.0 x 10- 14
• In neutral, acidic, or basic solutions, the Kw is
  always 1.0 x 10-14.
• Adding an acid to pure water - increases the
  H3O, causes the H3O to exceed 1.0 x 10-7 M,
  decreases the OH-.
• Adding a base to pure water - increases the
  OH-, causes the OH- to exceed 1.0 x 10- 7
  M, decreases the H3O.

11
Acids and Bases ionization constant in
calculations

• What is the H3O of a solution if OH- is 5.0
  x 10-8 M?
• STEP 1 Write the Kw for water.
• Kw H3O OH- 1.0 x 10-14
• STEP 2 Rearrange the Kw expression.
• H3O 1.0 x 10-14
• OH-
• STEP 3 Substitute OH-.
• H3O 1.0 x 10-14 2.0 x 10-7 M
• 5.0 x 10- 8

12
Acids and Bases pH scale

• The pH of a solution
• is used to indicate the acidity of a solution.
• has values that usually range from 0 to 14.
• is acidic when the values are less than 7.
• is neutral with a pH of 7.
• is basic when the values are greater than 7.

13
Acids and Bases pH and the hydronium ion
concentration

• pH is the negative log of the hydronium ion
  concentration.
• pH - log H3O
• Example For a solution with H3O 1 x 10-4
• pH -log 1 x 10-4
• pH - -4.0
• pH 4.0
• Note The number of decimal places in the pH
  equals the significant figures in the coefficient
  of H3O.
• 4.0 - 1 SF in 1 x 10-4
• H3O 1 x 10-4 pH 4.0
• H3O 8.0 x 10-6 pH 5.10
• H3O 2.4 x 10-8 pH 7.62

14
Acids and Bases pH and the hydronium ion
concentration
15
Acids and Bases reactions of acids with bases

• In a neutralization reaction
• an acid such as HCl reacts with a base such as
  NaOH.
• HCl H2O H3O Cl-
• NaOH Na OH-
• the H3O from the acid and the OH- from the base
  form water.
• H3O OH- 2
  H2O
• Write the neutralization reactions for stomach
  acid HCl and Mylanta.
• Mylanta Al(OH)3 and Mg(OH)2
• 3HCl(aq) Al(OH)3(aq) AlCl3(aq)
  3H2O(l)
• 2HCl(aq) Mg(OH)2(aq) MgCl2(aq)
  2H2O(l)

16
Acids and Bases Buffers
17
Acids and Bases Buffers

• Buffers
• resist changes in pH from the addition of acid or
  base.
• in the body, absorb H3O or OH- from foods and
  cellular processes to maintain pH.
• are important in the proper functioning of cells
  and blood.
• in blood maintain a pH close to 7.4. A change in
  the pH of the blood affects the uptake of oxygen
  and cellular processes.
• A buffer solution
• contains a combination of acid-base conjugate
  pairs.
• may contain a weak acid and a salt of its
  conjugate base.
• typically has equal concentrations of a weak acid
  and its salt.
• may also contain a weak base and a salt of the
  conjugate acid.

18
Acids and Bases Buffers

• In the acetic acid/acetate buffer with acetic
  acid (CH3COOH) and sodium acetate (CH3COONa)
• The function of the weak acid in a buffer is to
  neutralize a base. The acetate ion produced adds
  to the available acetate.
• CH3COOH OH- CH3COO- H2O
• acetic acid base
  acetate ion water
• The function of the acetate ion CH3COO- is to
  neutralize H3O from acids. The acetic acid
  produced contributes to the available weak acid.
• CH3COO- H3O CH3COOH H2O
• acetate ion acid
  acetic acid water

19
The biological carbonic acid/bicarbonate buffer.
the bicarbonate buffering system is open
because it is coupled to the lungs and kidneys.
Lungs maintain dissolved Co2 levels
Kidneys maintain bicarbonate and H levels
Carbonic Acid (H2CO3)
biocarbonate ion (HCO3-)
Blood (pH 7.4)
improper function
Respiratory Acidosis (inadequate CO2 excretion -
related to respiratory problems such as
asthma) Metabolic Acidosis - excessive H ion
production
acidosis - low blood pH alkalosis - high blood pH
Also respiratory and metabolic alkalosis.