Acid_ Bases_ and Salts

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					Acid, Bases, and Salts

    Chemistry—Part 1
                   I. Acids
H
  is a nonmetal or polyatomic ion
  could be Cl- , SO42-, etc.

Ex:   HCl, HF, H2SO4 , HClO4, H3PO4
                Acids (con’t)
dissociate to form H+ ions (protons)

Hydrogen Atom Hydrogen Ion (proton)
     e-
          +
          A. Ionization in Water
             HCl + H2O       H3O+ + Cl-
                              +
                                     -


H+ combines with H2O to form H3O+

                             Hydronium Ion

H+(proton) is attracted to lone e- pairs in H2O
                 Try This:
H2SO4 + 2H2O    2 H3O+ + SO42-
                 +
                       SO42-
    SO42-




                 +




H3PO4 + 3H2O        3 H3O+ + PO43-
                  B. Examples
•   Soda pop – H2CO3, H3PO4
•   Vinegar (acetic acid) – HC2H3O2
•   Lemons – citric acid
•   Stomach acid – HCl
•   Battery acid – H2SO4
•   Sour Patch Kids – Tartaric Acid
               C. Properties
• taste sour
• conduct electricity
• turn litmus red
• react with some metals to produce H2 (g)
  Remember,
    Zn + 2HCl  ZnCl2 + H2(g)
• corrosive
• All form H+ ions in solution
                 II. Bases
contain OH- (hydroxide ions)
Ex: Ca(OH)2, LiOH, NH4OH, NaOH
Also called alkaline (alkali)




                                 Alkali Flats
                                 Bonneville Salt Flats, Utah
          A. Ionization In Water
          H2O
NaOH             Na+ + OH-


          H2O
NH4OH             NH4+ + OH-
           H2O
Ca(OH)2            Ca2+ + 2 OH-
                 B. Examples
•   Drano – NaOH
•   Oven cleaner – KOH
•   Tums – Ca(OH)2
•   Glass cleaner – NH4OH
                  C. Properties
•   Taste bitter (Baking Soda)
•   Conduct electricity
•   Turn litmus blue
•   Feel slippery (hard to wash off of skin)
•   Caustic (dissolves protein, ie. YOU)
•   Form OH- ions
  III. Reactions of Acids and Bases
Neutralization:

     Acid + Base  Salt + Water

     HBr + NaOH       NaBr + H2O

Type of reaction? DOUBLE DISPLACEMENT!
              Try This:
HF   +   LiOH     HOH     +   LiF
                   (H2O)


H2SO4    + 2 KOH       2 H2O + K2SO4
                 Antacids
Neutralize stomach acid

Ex: Tums
2 HCl    +      Ca(OH)2  2 H2O + CaCl2

Milk of Magnesia (demo)
2 HCl+    Mg(OH)2          2 H2O + MgCl2
        IV. Electrolyte Solutions
Substances whose water solutions conduct
  electricity

  NaCl (c) vs. NaCl (aq)
  Sucrose (c) vs. Sucrose (aq)
  H2O (distilled) vs. H2O (tap)

     There must be ions present to conduct
     Strong & Weak Electrolytes
STRONG ELECTROLYTES
Ionize 100%              NaCl
                         (s)

      NaCl  Na+ + Cl-           Na+
                                  Na+
                                              Cl -

                                       Cl -


                          only ions are present
WEAK ELECTROLYTES
Only partially ionize                                HF (s)

     HF  H+ + F-                                              HF    F+

                                                              HF         HF
                                                                    H+

                                                      mostly HF present;
                                                      only some ions
        Conductivity Demo
NH4OH + HC2H3O2    H2O + NH4C2H3O2

Weak      Weak              Salt
Base      Acid
            Practice
  Salt      Parent Acid   Parent Base
              H?            ?OH
  LiBr       HBr            LiOH

 K2CO3
              H2CO3         KOH

(NH4)2SO4
              H2SO4          NH4OH
           Lab 49 Pre - Lab
NaCl  Na+ (aq) + Cl- (aq)
FeCl3  Fe3+ (aq) + 3 Cl- (aq)
C6H12O6  C6H12O6 (aq)
     V. Naming Acids, Bases & Salts
Acid Names
  1. Binary Acids
           contain only TWO elements
      ex: HCl    Hydrochloric Acid
                 Hydro-stem-ic Acid
      Try: HBr Hydrobromic Acid
           HF Hydrofluoric Acid
           H2S Hydrosulfuric Acid
1. Ternary Acids
     contain THREE elements (usually)
     contain H and a polyatomic ion

     ate  ic             ite  ous
   ex:    H2CO3      carbonate  carbonic
                     Carbonic Acid
                         Try These
HNO2
        nitrite  nitrous
                       Nitrous Acid
HNO3
        nitrate  nitric
                        Nitric Acid

H2SO3
        sulfite  sulfurous
                       Sulfurous Acid
H2SO4
        sulfate  sulfuric
                       Sulfuric Acid
  Base Names (IUPAC Nomenclature)

Combine names of ions

NaOH
          Sodium Hydroxide

Ca(OH)2
          Calcium Hydroxide
               Salt Names
Combine names of ions

 NaBr
         Sodium Bromide
 K2SO4
         Potassium Sulfate
 Cu(NO3)2
         Copper (II) Nitrate
                       VI. Salts
Salts are ionic and crystalline
         A. Dissociation in Water

         H2O
Salt             Cation + Anion

         H2O
LiCl              Li+   +    Cl-

           H2O
Na2SO4             2 Na+ + SO42-
          B. Cation and Anion
Cation: Positive (+) charge

The ___________ contributes the cation
     (acid/base?)

Anion: Negative (-) charge

The ___________ contributes the anion
     (acid/base?)
         C. Examples
            Cation     Anion

 NaCl
           Na+         Cl-
NaHCO3
           Na+         HCO3-
K2SO4       K+         SO42-
       Parent Acid / Parent Base
Parent Acid: The acid that contributes the
  ANION to the salt

Parent Base: The base that contributes the
  CATION to the salt
      VIII. Strong Acids and Bases
STRONG ACIDS—DISSOCIATE 100 %
    HCl      HNO3     H2SO4

STRONG BASES—DISSOCIATE 100%
    All Alkali Metals (IA) form strong bases
     VIII. Weak Acids and Bases
WEAK ACIDS—DO NOT DISSOCIATE 100 %

WEAK BASES—DO NOT DISSOCIATE 100%

How would a weak acid conduct electricity
 compared to a strong acid?
          IX. Polyprotic Acids
Acids with more than one proton (H+)

A. Examples

H2SO4     H3AsO4     H3PO4     H2CO3   H2S
      B. Step – By – Step Ionization
      Acids lose one proton at a time

1st   H3PO4  H+ + H2PO4-
2nd   H2PO4-  H+ + HPO4-2
3rd   HPO4-2  H+ + PO4-3

      H3PO4  3H+ + PO43-
  H3PO4 + 3 H2O        3 H3O+ + PO43-
                  Questions
1. Which of the following are polyprotic acids?
           a) HCl                 d) HC2H3O2
           b) NH3                 e) H3PO4
           c) H2SO4               f) HNO3

2. Which acid is harder to ionize: H3PO4 or HPO4-2?
  Why?
     The -2 charge attracts protons (H+)
3. Which acid is stronger: H2SO4 or HSO4-? Why?
     easier to lose protons (H+)
Lab 50 Answers
   Water as an acid and a base
amphoteric:
water behaves as an acid & base
  H 2O     +    H2O  H3O+ +     OH-




 acid         base      conj      conj
                        acid      base
              X. Anhydrides
Without water

Acidic Anhydrides—
  non-metallic oxides that combine with H2O to
  form an acid

 SO2 + H2O  H2SO3
 CO2 + H2O  H2CO3
      Acid Anhydrides
Basic Anhydrides—
  metal oxides that combine with H2O to form
  a base

 CaO + H2O  Ca(OH)2
 Na2O + H2O  2 NaOH

        Basic Anhydrides
 Try These: Acidic or Basic Anhydride?
K2O
      Basic Anhydride



NO2

      Acidic Anhydride
•   http://www.epa.gov/maia/images/acid.jpg
Acid, Bases, and Salts

    Chemistry—Part 2
                I. Molarity
Example: 6 M KOH    0.1 M H2SO4   2 M NaCl

A measure of concentration

           # moles
       M
          L solution
     Concentration




6M               1M
              Examples
3 M HNO3 =   3 moles HNO 3
              1 L solution


20 moles in 5 L = ? M

        20moles
                 4M
          5L
                  Try This!
If 80 grams of NaOH (MW=40) is dissolved in
   2 L, find the molarity.
   80 g                     2moles
            2moles                 1M
40 g / mol                   2L
6 moles of HBr in 250 ml. Molarity?

      6moles xmoles
                              x  24M
      250ml 1000ml
          Now Try This One!

                              moles
How many moles of       M
 HCl are in 500 ml of           L
 a 3 M solution?
                               xmoles
                        3M 
                                0. 5 L
                        x  1.5moles
                II. Titration
Using a solution of known concentration to
 determine the concentration of another
 solution.

A neutralization reaction
     Acid + Base  Salt + Water
                 End Point
The point at which neutralization is complete

moles H+ = moles OH-

use acid-base indicators (like phenolphthalein)
  to determine the end point
Acidic—
before
neutralization




 Neutral—
 ”End Point”




  Basic—
  “overshot
  endpoint”
NaOH  Na+ + OH-
            1M         50 ml
 1M

HCl  H+ + Cl-
                       50 ml
1M 1M

H2SO4  2 H+ + SO42-
                       25 ml
 1M     2M
NaOH  Na+ + OH-
             1M    50 ml
 1M

HCl  H+ + Cl-
                   25 ml
2M 2M
           Titration Equation

    M AVA # H   M BVB #OH 
MA = Molarity of Acid
VA = Volume of Acid
#H+= Number of H’s in acid formula
                        UNITS MUST MATCH!!!
           MB = Molarity of Base
           VB = Volume of Base
           #OH- = Number of OH’s in base formula
                    Try This
50 ml of 0.1 M NaOH is neutralized by 5 ml of
  HCl. Find the molarity of the acid.

          M AVA # H   M BVB #OH 
                                           
( M A )(5ml )(1H )  (0.1M )(50ml )(1OH )
       (5ml)(1H +)       (5ml)(1H+)
                    M A  1M
                   Try This
40 ml of 1M KOH is neutralized by 10 ml of
  sulfuric acid. Find the molarity of acid.

          M AVA # H   M BVB #OH 
                                             
( M A )(10ml )(2 H )  (1M )(40ml )(1OH )
       (10ml)(2H  +)      (10ml)(2H+)
                 M A  2M
               III. Indicators
Weak organic acids or bases that are a
 different color in an acid than in a base

Ex:
Phenolpthalein
Bromothymol Blue
Litmus
Red Cabbage
       Limitations of Indicators
Solutions must be colorless

Eye must be able to detect the change
        IV. Ionization of Water




                             [ ] stands for
                             concentration
In pure water, [H+] = 10-7 M and [OH-] = 10-7 M

1 water out of 10,000,000 forms ions
   Kw – water’s ionization constant
Kw = [H+] [OH-]
Kw = (10-7) (10-7)
Kw = 10-14

so…           CONSTANT

10-14 = [H+][OH-]
                     Add Acid? Add Base?
                 Example #1
[OH-] = 10-6 M      [H+] = ?

                              
      K w  [ H ][ OH ]
          14                 6
     10           [ H ][10 ]
                       8
     [ H ]  10 M
                    Example #2
[H+] = 10-3 M             [OH-] = ?

                                     
      K w  [ H ][ OH ]
          14              3             
     10          [10 ][ OH ]
                           11
     [OH ]  10                   M
                  pH Scale
Used to measure acidity

Based on the concentration of H+ ions
When
the [H+]
increases
by 10,
the pH
decreases
by 1.

When
the pH
increases
by 2,
the [H+]
decreases
by102 = 100
   _____
               pH = -log[H+]
[H+] = 10-4           4
               pH = ______     acidic or basic?

[H+] = 10-11          11
               pH = ______     acidic or basic?
               pOH = -log[OH+]
[OH-] = 10-3                3
                    pOH = ______

[H+] = 10-9                 5
                    pOH = ______
               pH + pOH = 14
Why?
                [H+] [OH-] = 10-14
       - log   (10-7) (10-7) = 10-14 - log

                 pH + pOH = 14
                Try These:
For a solution that is 0.1 M HCl…
1) What is the pH?
2) What is the concentration of OH- ions?
3) What is the pOH?
For a solution that is 0.001 M NaOH…
1) What is the pOH?
2) What is the pH?
3) What is [H+]?
For a solution that has a pH of 8…
1) What is the [H+]?
                 Hydrolysis
The reaction of a salt with water to form an
  acidic or basic solution

Recall Strong Acids: HCl       HNO3       H2SO4

Recall Strong Bases: Group IA Hydroxides
Look at the Parent Acid & Parent Base

   Salt     Parent Acid Parent Base

 Neutral      STRONG       STRONG

  Acidic      STRONG         weak

  Basic        weak        STRONG
                  Ex: NaF
Parent Acid: HF             strong or weak?

Parent Base: NaOH           strong or weak?



So…NaF is BASIC
               Try This: Fe(NO3)3
Parent Acid:    HNO3        strong or weak?

Parent Base: Fe(OH)3         strong or weak?



So…Fe(NO3)3 is ACIDIC
               Try This: NaCl
Parent Acid:   HCl        strong or weak?

Parent Base: NaOH          strong or weak?



So…NaCl is NEUTRAL

				
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