Acids and Bases

Common Acids in Foods
1.  citric acid - lemons, oranges, and grapefruit
2.  malic acid - apples
3.  acetic acid - vinegar
4.  lactic acid - sour milk
5.  tartaric acid - wine
6.  phosphoric acid - carbonated beverages

General Properties of Acids                                   General Properties of Bases
1.  taste sour                                                                                                            1.  taste bitter
2.  turn blue litmus paper pink                                                                              2.  turn red litmus paper blue
3.  keep phenolphthalein colorless (indicator)                                                   3.  turns phenolphthalein pink (indicator)
4.  react with metal to give off H2 gas                                                                 4.  do not react react to give off H2 gas
5.  feel like water                                                                                                      5.  feels slippery
6.  strong acids are corrosive                                                                                6.  strong bases are corrosive
7.  considered electrolytes                                                                                     7.  considered electrolytes

Definitions Associated with Acids and Bases
dilute:  small amount of solute (acid or base) in a large amount of solvent (water).
concentrated:  large amount of solute (acid or base) in a certain amount of solvent (water).
indicator:  compound that changes color to show the presence of an acid or base.
corrosive:  eating away or wearing away.

Definitions of Acids
1.  Arrhenius Acid:  contains H and ionizes in aqueous solution to form H+ .  H+ is usually in the form of the hydronium ion.
                                 Hydronium ion:  H3O+ ;  it is formed when H2O gains another H.

    example:   HNO3     +      H2         H3O+     +       NO3-
                      Acid
 

2.  Bronsted-Lowery Acid:  proton donor (hydrogen donor); This means it gives up a proton (H) to another compound.

    example:   HCl        +      NH3      NH4+      +       Cl-
                      Acid

3.  Lewis Acid:  electron pair acceptor

    example:  BF3     +     NH3         F3BNH3
 
 
 
 
 

    BF3  is the electron pair acceptor.  Therefore, it is an acid.

Types of Aqueous Solutions
1.  strong acids:  strong electrolytes and ionize 100% in aqueous solution.

2.  weak acids:  weak electrolytes and don't ionize 100% in aqueous solution.
 
 
Strong Acids
Weak Acids
HClO4
H3PO4
HCl
HF
HNO3
CH3COOH
H2SO4
HCN
 
H2S
 
H2CO3

 Types of Acids based on # of Hydrogens
1.  monoprotic acid:  only 1 proton (H) to donate.  Ex.   HF, HCl, HNO3

2.  diprotic acid:  2 protons (H) to donate.  Ex.  H2SO4 , H2CO3 , H2S

3.  triprotic acid:  3 protons (H) to donate.  Ex.  H3PO4

polyprotic acid:  can donate more than 1 proton (H).  Diprotic and triprotic acids are polyprotic.

Other Acids
1.  organic acid:  compound containing C and H along with a carboxyl group ( -COOH)
                              Ex.  CH3COOH (acetic acid)

2.  mineral acid:  acids made from minerals.
                             Ex.  sulfuric acid, nitric acid, and phosphoric acid

Names and Structures of Common Acids
1.  binary acids:  contain H and only one other element
                               Ex.  HF, HCl, HBr, HI

    Naming Binary Acids

    Prefix:  hydro-
    root:  root of element name
    suffix:  -ic
 
 
Formula
Name of Acid
HF
hydrofluoric acid
HCl
hydrochloric acid
HBr
hydrobromic acid
HI
hydroiodic acid
H2S
hydrosulfuric acid

2.  oxyacids:  contains H, O, and a third element.

    Naming Oxyacids

    ending of ion       suffix
    - ite                         - ous
    - ate                        - ic
Acid
Name of Anion
Name of Acid
H2CO3 carbonate carbonic acid
HIO3 iodate iodic acid
H3PO4 phosphate phosphoric acid
H3PO3 phosphite phosphorous acid
H2SO4 sulfate sulfuric acid
H2SO3 sulfite sulfurous acid
HNO3 nitrate nitric acid
HNO2 nitrite nitrous acid
HClO hypochlorite hypochlorous acid
HClO2 chlorite chlorous acid
HClO3 chlorate chloric acid
HClO4 perchlorate perchloric acid

3.  ternary acids:  acids containing H and a polyatomic ion.

    They are named the same way as oxyacids.

Some Common Acids
sulfuric acid:  (H2SO4)                                                                                               phosphoric acid:  (H3PO4)
1.  used in manufacturing fertilizer                                                                            1.  used to flavor beverages
2.  used in production of paint, dye, and metal                                                       2.  used in manufacturing of detergents and ceramics
3.  known as "battery acid"                                                                                        3.  dilute H3PO4 is not toxic
4.  very strong, causes severe burns
5.  used to dehydrate compounds (remove water)

nitric acid:  (HNO3)                                                                                                       hydrochloric acid:  (HCl)
1.  used in making explosives, rubber, plastics,                                                         1.  produced in the stomach
     dyes, and drugs                                                                                                         2.  used in pickling iron and steel (remove impurities from surface of metal)
2.  causes serious burns

acetic acid:  (CH3COOH)
1.  produced by fermentation of malt, barley, and fruit juices
    to make vinegar
2.  raw material in production of food supplements (lysine)

Some Common Bases
1.  household ammonia
2.  lye (sodium hydroxide)
3.  milk of magnesia
4.  Maalox

Definitions of Bases
1.  Arrhenius Base:  contains OH and produces OH- in solution.

    example:   NaOH    Na+    +    OH-

    alkaline:  solution that contains OH- from a base

    neutralization:  reaction of H3O+ and OH- to form water.  (when an acid and base react to form water and a salt)

     example:   H3O+     +      OH-       2 H2O

    salt:  ionic compound composed of a metal cation from a base and the anion from an acid.

2.  Bronted-Lowery Base:  proton (H) acceptor.

     HCl     +     NH3        NH4+          +       Cl-
    Acid           Base

3.  Lewis Base:  electron pair donor.

   BF3     +     NH3         F3BNH3
 
 
 
 

    BF3  is a Lewis acid.   NH is a Lewis base.

Strength of  Bases
Group 1 and Group 2 hydroxides are considered strong.  All others are considered weak.

Conjugate Acids and Conjugate Bases
conjugate acid:  formed when a base gains a hydrogen.

conjugate base:  formed when an acid donates a hydrogen.

NH3     +       H2      NH4+         +       OH-
base             acid                          conjugate            conjugate
                                                       acid                        base

HCl      +    H2      H3O+         +        Cl-
acid           base                            conjugate            conjugate
                                                       acid                      base

*** Strong acids have weak conjugate bases.
*** Strong bases have weak conjugate acids.

amphoteric:  substances that can act as an acid or a base.  The best example is water.

Ex.  Water as a base

        H2SO4      +      H2      H3O+      +      HSO4-
        acid                    base                    conjugate        conjugate
                                                                acid                  base

Ex.  Water as an acid

       NH3      +       H2O             NH4+     +    OH-
       base               acid                               conjugate      conjugate
                                                                     acid                base