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					Lecture Unit 7 RegalChem
Quarter Lines on Note Sheets!
 New Semester…New Year
     New Commitment!
           In This Unit...
We learn a few more household chemicals
We go back and review how things
 dissolve AND how to write equations
 describing them
We learn how to tell if a particular SALT
 will dissolve in water
We see acids and bases in a little more
 detail and learn the six nastiest acids out
 there!
7 New Chemicals to learn (or put
          on 3X5 card)
1. NH3 (ammonia) poisonous
 household cleaner
the famous ALKANES
2. CH4 (methane)
3. C3H8 (propane)
4. C8H18 (octane)
the famous ALCOHOLS
5. CH3OH methyl alcohol
6. C3H7OH propyl alcohol
7. C2H5OH ethyl alcohol
notice how alcohols are an
 alkane with an OH in place
 of one hydrogen
        Remember...
aqueous salt solutions have
 the ions floating around in
 the water separately, not as
 bonded salt particles
                     In solutions, the
NaCl(s)             lattice breaks up!


    Na+          Cl-(aq)     +
          (aq)             Na    (aq)
                      Cl-(aq)

The ions are not connected
When salts dissolve (become clear
 in water), they do it because they
 break up into charged ions
This is called “dissociation” or
 “ionization”
YOU TRY…draw of calcium nitrate
 ionizing in a beaker of water
Know the formula???
Ca(NO3)2
When molecules dissolve, they
 do not ionize.
The entire molecule breaks out
 of the crystal lattice and
 travels around the water as a
 neutral particle.
 In solns, the lattice breaks up!
(C12H23O11)(s)




The molecules don’t make ions
YOU TRY. Show some ammonia
 gas dissolving in water.
NOW, we can also write
 “dissolving” and “dissociation”
 equations for these.
NaCl(s) -->   +
            Na (aq)  +   Cl -
                                (aq)
NH3 (g) --> NH3 (aq)
Lecture Break
You TRY…
1. Write DISSOCIATION equations for
  each one of these ionic compounds in
  water. KBr Na2SO4 Fe(OH)3
2. Write DISSOLVING equations for
  each one of these molecular compounds
  in water CH3OH PCl3 SiH4
           Definitions
Soluble - a cmpd which will break
 up its lattice in water.
Slightly soluble or insoluble -
 synonyms meaning a cmpd which
 will maintain lattice in water
Ionization or dissociation -
 when a salt breaks up into its
 ions. Only salts can dissociate
Dissolving - when any
 chemical dissolves in water.
 Molecules dissolve, but don’t
 dissociate. Salts do both.
Things that have dissociated
 conduct electricity.
 What happens when you
 mix two aqueous salts?
A “double displacement,”
 with 2 possible results
1. nothing (“no reaction”)
2. a precipitate will form and
 you will see a cloud form.
 How to tell if a salt ppt is possible
Write the equation that describes the
 reactants
Figure out possible new salts
Check “solubility table” in text (218
 NB, 183 OB) to see if new cmpds
 will be soluble or insoluble.
Let’s just practice reading the table.
P 195 OB 11-16
then write and balance the
 equation including the new
 products.
Let’s do one on board!
Ex “What will happen when you
 mix aqueous solutions of sodium
 bromide and lead (II) nitrate?”
          YOU TRY...
“Aqueous solutions of magnesium
iodide and silver nitrate are mixed.
Write the balanced equation for
         this process.”
   (OB p. 188, now please)
        S/C 7.1 together
Lecture Break
There are 3 ways to write all this
1. formula equation (“molecular
 equations” in book)- equation
 written with the complete
 formulas for the salts.
2. complete ionic equation - eqn
 written with the aqueous salts
 ionized
[spectator ions - ions which remain in
  solution during reaction and never
  become part of a precipitate.]
3. net ionic equation - eqn
 written without showing
 spectator ions.
New Book Ch 8, probs 8-16
 cover this stuff.
Notice how we focused on if a
 SALT is water soluble.
There will be an explanation for
 MOLECULES in another unit
Let’s PRACTICE
OB Ch 7 17,18,42,43,46,51,54,58,59
Lecture Break
   NO NOTES REVIEW When
         things dissolve?..
The crystal lattice breaks down
A clear solution is produced
If molecular solute (thing that got
  dissolved), the particles are
  neutral
If ionic solute (salt), particles are
  charged ions
flow charts help to make this clear
  Ch 8 probs17-23
         2 solute types
yield charged ions…(salts)
Or neutral particles (molecules)
Only salt solutions conduct
 electricity
Electrolytes--solutes that yield
 an electrically conductive
 solution. Almost always
 some sort of salt.
Non-electrolytes--solutes that
 yield a non-conductive
 solution. Usually molecules.
Strong electrolyte--solute that
 COMPLETELY dissociates
 when it dissolves. Soluble
 salts are strong electrolytes.
Weak electrolyte--solute that
 dissolves, but does not
 completely dissociate into
 ions. (Example coming)
        Acids and Bases
Acids-yield H + in water.

So they POSSIBLY can be
 ionic.
Many dissolve well, but
 DISSOCIATION is variable
 in acids
     Vinegar, a Weak Acid
(HC2H3O2 )--- it all dissolves,
 but a little dissociates to yield
 H + and C H O - ions.
            2 3 2
Vinegar only slightly conducts
 electricity
“weak” electrolyte
HC2H3O2(aq) -->H+ (aq)+C2H3O2- (aq)
(99.982%)      (.018%)
 Household vinegar is only
     0.018% ionized
     Sulfuric Acid H2SO4
As it dissolves, it fully
 dissociates
100% H   + and SO 2-
                   4
“strong acid”.
  H2SO4 --->2H++  SO4 -2

  (0%)         (100%)
All strong acids100% ionize
in water.
The H  + ions make the acids

very reactive
The 6 strong Acids(memorize!)
nitric, sulfuric, perchloric
hydrochloric, hydrobromic,
 hydroiodic
All other acids are weak
              BASES
BASE made of [cation] + OH -

So it is a type of salt
If it dissolves, it MUST
  dissociate, too.
Strong bases
  dissolve/dissociate,
Weak bases do NEITHER
ACID + BASE --> SALT + H2O
Strong bases: all group I & II
 hydroxides EXCEPT
 Be(OH)2 and Mg (OH)2
(“Be My Girl”)
All other hydroxides insoluble
and are WEAK bases (no loose
 OH  -)
Show strong/weak BASES as solid
 hydroxides ionizing
Fe(OH)2(s)--> Fe+2(aq) + 2OH-(aq)
Show strong/weak ACIDS as
 aqueous molecules going to ions
H2CO3(aq)_--> 2H+(aq) + CO32-(aq)
(there are just a few exceptions)
The End!!

				
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posted:5/7/2013
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