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Acids and Bases

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Title: PowerPoint Presentation Author: Christina Hantgin Last modified by: Windows User Created Date: 7/10/2001 11:23:53 PM Document presentation format – PowerPoint PPT presentation

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Title: Acids and Bases


1
Acids and Bases
2
Acids Compounds that contain one or more
hydrogen ions (H) when dissolved in
water Bases Compounds that contain one or
more hydroxide ions (OH-) when dissolved in water
3
Arrhenius Acid
A substance that dissociates in water to form
hydrogen ions (H) that is, an acid increases
the concentration of H ions in an aqueous
solution
4
Arrhenius Base
a substance that dissociates in water to form
hydroxide (OH-) ions that is, a base increases
the concentration of OH- ions in an aqueous
solution.
5
Bronsted-Lowry Acid
A molecule or ion that is able to lose, or
"donate," a hydrogen cation (proton,
H) acidbase ? conjugate baseconjugate
acid. The conjugate base is the ion or molecule
remaining after the acid has lost a proton, and
the conjugate acid is the species created when
the base accepts the proton. The reaction can
proceed in either forward or backward direction
in each case, the acid donates a proton to the
base.
6
Bronsted-Lowry Base
Substance with the ability to gain, or "accept,"
a hydrogen cation (proton, H).
7
Properties of Acids
  • Acids taste sour
  • Acids have a pH lower than 7
  • Acids effect indicators
  • Blue litmus turns red
  • Universal indicator turns red
  • Acids are proton (hydrogen ion, H) donors
  • Acids react with active metals, produce H2
  • Acids react with carbonates
  • Acids neutralize bases

8
Acids Have a pH less than 7
9
Acids React with Active Metals
Acids react with active metals to form salts and
hydrogen gas.
Mg 2HCl ? MgCl2 H2(g)
10
Acids Neutralize Bases
HCl NaOH ? NaCl H2O
Neutralization reactions ALWAYS produce a salt
and water.
11
Acids you must know
Strong Acids
Weak Acids
Sulfuric acid, H2SO4
Phosphoric acid, H3PO4
Hydrochloric acid, HCl
Acetic acid, HC2H3O2
Nitric acid, HNO3
12
Sulfuric Acid
  • Highest volume production of any chemical in the
    U.S.
  • Used in the production of paper
  • Used in production of fertilizers
  • Used in petroleum refining

13
Nitric Acid
  • Used in the production of fertilizers
  • Used in the production of explosives
  • Nitric acid is a volatile acid its reactive
    components evaporate easily
  • Stains proteins (including skin!)

14
Hydrochloric Acid
  • Used in the pickling of steel
  • Used to purify magnesium from sea water
  • Part of gastric juice, it aids in the digestion
    of protein
  • Sold commercially as Muriatic acid

15
Phosphoric Acid
  • A flavoring agent in sodas
  • Used in the manufacture of detergents
  • Used in the manufacture of fertilizers
  • Not a common laboratory reagent

16
Acetic Acid
  • Used in the manufacture of plastics
  • Used in making pharmaceuticals
  • Acetic acid is the acid present in vinegar

17
Acids are Proton Donors
Monoprotic acids
Diprotic acids
Triprotic acids
HCl
H2SO4
H3PO4
HC2H3O2
H2CO3
HNO3
18
Ionization of HCl and formation of hydronium ion,
H3O
H2O HCl ?
H3O Cl-
Proton donor
Proton acceptor
19
Strong Acids vs. Weak Acids
Strong acids are assumed to be 100 ionized in
solution (good proton donors).
HCl
H2SO4
HNO3
Weak acids are usually less than 5 ionized in
solution (poor proton donors).
H3PO4
HC2H3O2
Organic acids
20
Strong Acid Dissociation
21
Weak Acid Dissociation
22
Effects of acid on the Environment
  • Rainwater is naturally acidicWHY?When CO2 (gas)
    H2O H2CO3 (aqueous) react they formCarbonic
    acid Carbon dioxide (from the air) dissolves
    inrainwater, producing carbonic acid, a weak
    acid The normal pH of rainwater is about 5.6

23
Effects of acid on the Environment
  • Acid rain is rain with a pH less than 5.
  • Forms when air-polluting gases dissolve in
  • Rainwater
  • Sulfur dioxide (SO2) Further lowers the pH of
    rain.

24
Effects of acid on the Environment
  • Environmental Impact of Acid Rain
  • Dependent on local geology
  • Hill Country soil is rich in limestone (CaCO3),
    which is basic
  • Limestone neutralizes the effect of acid rain on
    lakes

25
Damages Caused by Acid Rain1) Damage to aquatic
life
  • In some sensitive lakes and streams,
    acidification has completely eradicated
  • fish species, such as the brook trout, leaving
    these bodies of water barren. Hundreds of the
    lakes in the Adirondacks have acidity levels
    unsuitable for the survival of fish

26
Damages Caused by Acid Rain (Cont.)2.) Damage to
vegetation
27
Damages Caused by Acid Rain (Cont.)3) Damage to
outdoor artwork (monuments statues)
28
Properties of Bases
  • Bases taste bitter
  • Bases have a pH greater than 7
  • Bases effect indicators
  • Red litmus turns blue
  • Universal indicator turns blue
  • Phenolphthalein turns purple
  • Bases are proton (H) acceptors
  • and usually have hydroxide ions- OH-
  • Solutions of bases feel slippery
  • Bases neutralize acids

29
Examples of Bases
  • Sodium hydroxide (lye), NaOH
  • Potassium hydroxide, KOH
  • Magnesium hydroxide, Mg(OH)2
  • Calcium hydroxide (lime), Ca(OH)2

30
Bases Effect Indicators
Red litmus paper turns blue in contact with a
base.
Phenolphthalein turns purple in a base.
31
Bases have a pH greater than 7
32
Bases Neutralize Acids
Milk of Magnesia contains magnesium hydroxide,
Mg(OH)2, which neutralizes stomach acid, HCl.
2 HCl Mg(OH)2
MgCl2 2 H2O
33
Products of Neutralization
HCl NaOH ?
NaCl H2O
H2SO4 Ca(OH)2 ?
CaSO4 2 H2O
HNO3 KOH ?
KNO3 H2O
The products of neutralization are always a
______ and _______.
salt
water
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