Acids and Bases

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Unit 13

• Acids and Bases

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Properties
ACIDS
BASES

• electrolyte

• electrolyte

• sour taste

• bitter taste

• slippery feel

• sticky feel

• turn litmus blue

• turn litmus red

• react with acids to form water and a salt (ionic
  compound)

• react with bases to form water and a salt (ionic
  compound)

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Examples

• ACIDS Most citrus fruits, tea, battery acid,
  vinegar, milk, soda, apples.
• BASES Common household bases include baking
  soda, lye, ammonia, soap, and antacids.
• .

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Indicators

• Indicators are substances that change color in
  the presence of an acid or a base
• Indicators are made up of weak acids or weak
  bases
• Examples of indicators include pH paper, red and
  blue litmus paper, and phenolphthalein

5

• Acids Affect Indicators
• Blue litmus paper turns red in contact with an
  acid. It remains blue when in contact with a base
  or neutral solution.

6

• Bases affect indicators

Red litmus paper turns blue in contact with a
base. It remains red when in contact with an acid
or neutral solution.
Phenolphthalein turns pink in a base. It is
colorless in an acid or neutral solution.
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Definitions

• There are 3 definitions used to describe acids
  and bases
• Arrhenius
• BrØnsted-Lowry
• Lewis
• The most traditional is Arrhenius acids and
  bases.

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Definitions

• Arrhenius - In aqueous solution

• Acids form hydrogen ions (H)

HCl H2O ? H Cl
Also called hydronium ions (H3O)
acid
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Definitions

• Arrhenius - In aqueous solution

• Bases form hydroxide ions (OH-)

NH3 H2O ? NH4 OH-
base
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Definitions
Another common way to refer to hydrogen ions is
to call them protons

• Brønsted-Lowry

• Acids are proton (H) donors.
• Bases are proton (H) acceptors.

HCl H2O ? Cl H3O
base
acid
Conjugate acid particle formed when a base
gains a H Conjugate base particle that remains
when an acid has donated a H

• .

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Definitions

• Lewis

• Acids are electron pair acceptors.
• Bases are electron pair donors.

Lewis base
Lewis acid
12
White Board Questions

• When you wafted a substance your nose burned.
  Would this substance be an acid or a base?
• A hydrogen ion (H) can also be called a
  _________ or ____________.
• Arrhenius acids are compounds that break up in
  water to give off _____________.
• What color litmus paper would you use to test an
  acid? What color will it turn?
• 5. If your food tastes bitter, which do you think
  it could possibly be an acid or a base?

ACID
H3O
Proton
H
Blue turns red
BASE
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White Board Questions

• 6. A BrØnsted-Lowry base _________ hydrogen
  ions.
• 7. Phenolphthalein turns pink when it comes in
  contact with a(n) _________.
• 8. Which of the scientists defined the typical
  acid?
• 9. If you are eating and it has a sour taste,
  would that be an acid or a base?
• 10. If a piece of red litmus paper turns blue
  than it is a(n) ___________.

accepts
base
Arrhenius
acid
base
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Naming Acids

• Binary acids
• Contains 2 different elements H and another
• Always has hydro- prefix
• Root of other elements name
• Ending -ic

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Examples of Binary Acids

• HI is hydroiodic acid
• H2S is hydrosulfuric acid
• HBr is hydrobromic acid
• HCl is hydrochloric acid

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Naming Acids

• Ternary Acids - Oxyacids
• Contains 3 different elements H, O, and another
• No prefix
• Name of polyatomic ion (p. 147)
• Ending ic for polyatomic ion ending in -ate
  and ous for ion ending in -ite

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Examples of Ternary Acids

• ClO3 is chlorate so HClO3 is chloric acid
• PO4 is phosphate
• so H3PO4 is phosphoric acid
• PO3 is phosphite
• so H3PO3 is phosphorous acid
• NO2 is nitrite HNO2 is nitrous acid
• NO3 is nitrate HNO3 is nitric acid

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Naming Acids cont.

• HC2H3O2 or CH3COOH
• Name is acetic acid
• Common name vinegar

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Practice Naming Acids

• H2SO3
• Sulfurous acid
• HF
• Hydrofluoric acid
• H2Se
• Hydroselenic acid

• Perchloric acid
• HClO4
• Carbonic acid
• H2CO3
• Hydrobromic acid
• HBr

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Ion Product of Water

• Self- ionization of water the simple
  dissociation of water
• H2O H OH-
• Concentration of ea. ion in pure water
• H 1.0 x 10-7M OH- 1.0 x 10-7M
• Ion-product constant for water (Kw), Where Kw
  1.0 x 10-14
• Kw H OH-
• Acid H gt OH-
• Base H lt OH-
• Neutral H OH-

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Calculating H and OH-

• reverse the pH equation
• The pH of a solution is 8. Find the H and
  OH- and determine whether it is acidic, basic,
  or neutral.
• basic

H 1 x 10-pH and OH- 1 x 10-pOH
H 1 x 10-8 M OH- 1 x 10-(14-8) M 1 x
10-6 M
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Examples

• 1. If the H in a solution is 1.0 x 10-5M, is
  the solution acidic, basic or neutral?
• 1.0 x 10-5 M
• What is the concentration of the OH-?
• Use the ion-product constant for water (Kw)
• Kw H OH-
• 1.0 x 10-14 1.0 x 10-5 OH-
• 1.0 x 10-14 OH-
• 1.0 x 10-5
• 1.0 x 10-(14-5)

pH 5 acidic
1.0 x 10-9 M
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Examples

• 2. If the pH is 9, what is the concentration of
  the hydroxide ion?
• Kw H OH-
• 1.0 x 10-14 M 1.0 x 10-9M OH-
• 1.0 x 10-5 M OH-

14 pH pOH
14 9 pOH
5 pOH
3. If the pOH is 4, what is the concentration of
the hydrogen ion? Kw H OH- 1.0 x
10-14 M H 1.0 x 10-4 M 1.0 x 10-10 M
H
14 pH pOH
14 pH 4
10 pH
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Examples

• 4. A solution has a pH of 4. Calculate the pOH,
  H and OH-. Is it acidic, basic, or neutral?
• 14 pH pOH
• 14 4 pOH
• 10 pOH
• Acidic since pH is 4

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Practice Problems

• Classify each solution as acidic, basic or
  neutral.
• 1. H 1.0 x 10-10 M
• 2. H 0.001M
• 3. OH- 1.0 x 10-7 M
• 4. OH- 1.0 x 10-4 M

Basic pH 10
1.0 x 10-3 acid pH 3
Neutral
14pH4 base pH 10
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OH- pOH pH H
1 x 10-14 14 0 1 x 100
1 x 10-13 13 1 1 x 10-1
1 x 10-12 12 2 1 x 10-2
1 x 10-11 11 3 1 x 10-3
1 x 10-10 10 Increasing acidity 4 1 x 10-4
1 x 10-9 9 5 1 x 10-5
1 x 10-8 8 6 1 x 10-6
1 x 10-7 7 Neutral 7 1 x 10-7
1 x 10-6 6 8 1 x 10-8
1 x 10-5 5 9 1 x 10-9
1 x 10-4 4 Increasing basicity 10 1 x 10-10
1 x 10-3 3 11 1 x 10-11
1 x 10-2 2 12 1 x 10-12
1 x 10-1 1 13 1 x 10-13
1 x 100 0 14 1 x 10-14
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White Board Practice Fill in the chart.
OH- pOH pH H
8
1x 10-12
10
1 x 10-3
1.0 X 10 -8
1.0 X 10 -6
6
2
12
1.0 X 10 -2
1.0 X 10 -4
1.0 X 10 -10
4
11
1.0 X 10 -11
3
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Fill in the chart.
OH- pOH pH H
8
1x 10-12
10
1 x 10-3
5
1 10-1
1.0 X 10 -8
1.0 X 10 -6
6
2
12
1.0 X 10 -2
1.0 X 10 -4
1.0 X 10 -10
4
11
1.0 X 10 -11
3
9
1.0 X 10 -5
1.0 X 10 -9
1
13
1.0 X 10 -13
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Strength or Concentration

• Strong Acid/Base
• Ionize completely in water
• strong electrolyte

Acids HCl HNO3 H2SO4 HBr HI HClO4
Bases NaOH KOH Ca(OH)2 Ba(OH)2
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Strength or Concentration

• Weak Acid/Base
• ionize partially in water
• weak electrolyte

Acids HF CH3COOH H3PO4 H2CO3 HCN
Base NH3
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Strength or Concentration

• How strong or weak an acid or base is, depends
  on its degree of ionization.

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pH Scale

0
14
7
INCREASING ACIDITY
INCREASING BASICITY
NEUTRAL
pH is the negative logarithm of the hydrogen ion
concentration
pH -logH
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The pH Scale
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pH Scale

• pH of Common Substances

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pH formulas
pH -logH pOH -logOH- pH pOH 14
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Neutralization

• Chemical reaction between an acid and a base.
• Products are a salt (ionic compound) and water.

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Neutralization

• ACID BASE ? SALT WATER

HCl NaOH ? NaCl H2O
strong
strong
neutral
HC2H3O2 NaOH ? NaC2H3O2 H2O
weak
strong
basic

• Salts can be neutral, acidic, or basic.

• Neutralization does not mean pH 7.

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Titration

• Titration
• Analytical method in which a standard solution is
  used to determine the concentration of an unknown
  solution.

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Titration cont.

• Equivalence point (endpoint)
• Point at which equal amounts of H and OH- have
  been added.
• Determined by
• indicator color change

• dramatic change in pH

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Titration formula
moles H moles OH- M?V? n M?V? n
M Molarity V volume n of H ions in the
acid or OH- ions in the base
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Titration example

• 42.5 mL of 1.3M KOH are required to neutralize
  50.0 mL of H2SO4. Find the molarity of H2SO4.

H2SO4 M ? V 50.0 mL n 2
KOH M 1.3M V 42.5 mL n 1
MVn MVn M(50.0mL)(2)(1.3M)(42.5mL)(1)
M 55.25 100
M 0.55M H2SO4
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Review of Acid and Base Definitions

• Arrhenius
• Most specific/exclusive definition
• Created by Svante Arrhenius, Swedish
• Acid compound that creates H in an aqueous
  solution
• HNO3 ? H NO3-
• Base compound that creates OH- in an aqueous
  solution
• NaOH ? Na OH-

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Review of Acid and Base Definitions

• Bronsted-Lowry
• More general definition than Arrhenius definition
• Most commonly used definition
• Created by 2 scientists around the same time
  (1923)
• Acid Molecule or ion that is a proton (H) donor
• HCl H2O ? H3O Cl-
• Base Molecule or ion that is a proton (H)
  acceptor
• NH3 H2O ? NH4 OH-

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Review of Acid and Base Definitions

• Lewis
• Most general definition
• Defined by electrons and bonding rather than H
• Created by the same scientist who electron-dot
  diagrams are named after
• Acid atom, ion, or molecule that accepts an
  electron pair to form a covalent bond
• NH3 Ag ? Ag(NH3)2
• Base atom, ion, or molecule that donates an
  electron pair to form a covalent bond
• BF3 F- ? BF4-