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Chapter 11 Chemistry

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									Chapter 11 Chemistry


   Chemical Reactions
11.1 Describing Chemical Reactions
n Reactants are on the left side of the equation.
n Products are on the right side of the equation.
n A skeleton equation is a chemical equation that does 
  not indicate the relative amounts of the reactants and 
  products.
n A catalyst is a substance that speeds up the reaction 
  but is not used up in the reaction.
n See Table 11.1 on page 323 for Symbols used in 
  chemical equations.
11.1 cont
n To write a balanced chemical equation, first 
  write the skeleton equation. Then use 
  coefficients to balance the equation so that it 
  obeys the law of conservation of mass.
  n   H2  + O2  à H2O

  n   2H2  +  O2  à 2H2O
Conceptual Problem 11.2
Practice Problem #3 page 327
Practice Problem #4 page 327
Practice problem #5 page 328
Practice problem #6 page 328
   Predicting Products



(AKA:  Soap opera Chemistry)
Five types of reactions:
• Synthesis (Combination)
• Decomposition
• Single Replacement
• Double Replacement
• Combustion
1. Synthesis (or Combination)

 Two or more substances react 
            to form
         ONE product

              A + B à AB
  The soap opera begins . . .

Rob    + Sally    à Rob/Sally


      +          à
 Demo #1: Synthesis Reaction


Remember to balance the equation!

 2 Mg(s) +    O2(g)   à 2 MgO
                              (s)
2. Decomposition

A compound breaks down into 
     simpler substances.
A decomposition reaction requires heat, 
  light, electricity, or a chemical catalyst

            AB à A + B
Drama with Rob and Sally .
..
Rob/Sally à Rob       + Sally



           à          +
 Demo #2: Decomposition Reaction


Remember to balance the equation!

             
                KI
2 H2O2(aq) à 2 H O + O
                2 (l)  2(g)
       3. Single Replacement Reaction
n Atoms in single element replace the atoms in a 
  compound
n Can be cationic or anionic . . .
   n A metal replaces the cation in the compound
   n A nonmetal replaces the anion in the compound

   Cationic SR:    A is a metal element, B is cation (+)
     A +BC à  AC + B   
   Anionic SR: C is a non-metal element, D is anion (-)
     C + BD à  BC +  D
How can you know if one metal
will displace another?
                                                 Li
n Look on the Activity Series of 
                                                 K
  Metals Chart . . .  Page 333. (Compare 
  this with your PT)                             Ca
n A reactive metal will replace any              Na
  metal listed below it.  
                                                 Mg
   Will this React?                              Al
   Mg +   ZnCl2 à       YES !
                                                 Zn
                         MgCl2 + Zn
   Will this React?                              …

   Mg +   CaCl2 à
                        NO Reaction! Mg is lower than Ca
   Along comes Brian . . .

Brian   + Rob/Sally à Brian/Sally + Rob



        +          à             +
 Demo #3: Single Replacement Reaction


  Mg(s) +   2 HCl(aq) à MgCl2(aq)   +   H2(g) 


Demo #4: Single Replacement Reaction


                        +
2Al + 3 CuCl 2 à 2 AlCl 3 3Cu

Remember to balance the equation!
4. Double Replacement Reaction

 Compounds exchange cations

     AB + CD à  CB  +  AD
   Drama at the prom . . .

Rob/Pam + Brian/Sally à Brian/Pam + Rob/Sally


         +                       +
                     à
               Demo #5:
      Double Replacement Reaction


               2        2
Pb(NO3)2(aq) +   KI(aq)à   KNO3(aq) + PbI2(s) 




  Remember to balance the equation!
 5. Combustion
An element or compound reacts with O2 
  producing energy as heat and light.

  Example:  Mg(s) +  O2(g) à  MgO(s)

Complete combustion of a hydrocarbon yields 
 CO2 and H2O

  Example:  C3H8 + O2 à CO2 + H2O
  The Soap opera Ends L

  Brian    +     O2   à    CO2  +  H2O
(A hydrocarbon)
                                         Oh No!




                       à
 Demo#6: Combustion

 To get our H2, we will first do a single 
   replacement reaction:
        2
 Zn    +   HCl  à   ZnCl2     +     H2   
  
         H2 + O2   à    H2O  + Energy!
     2             2


Remember to balance the equation!
Homework 11.1 and 11.2
n Review worksheet 11.1 and 11.2
n Section Assessment 7-12 page 329
n Section Assessment 22-27 page 339
Section 11.3 Reactions in Aqueous
Solutions
n A complete ionic equation is an equation that 
  shows dissolved ionic compounds as 
  dissociated free ions.
n Ex


n An ion that appears on both sides of an 
  equation and is not directly involved in the 
  reaction is called a spectator ion.
11.3 Cont.
n The net ionic equation is an equation for a 
  reaction in solution that shows only those 
  particles that are directly involved in the 
  chemical change.
n Ex.
Conceptual Problem 11.9 page 343
Practice problem #28 page 343
Practice Problem #29 page 343
11.3 Cont.
n You can predict the formation of a precipitate 
  by using the general rules for solubility on 
  ionic compounds.  Table 11.3 page 344.
Table 11.3
           Compounds                     Solubility


Salts of alkali metals and                Soluble
ammonia

Nitrate salts and chlorate salts          Soluble


Sulfate salts, except compounds           Soluble
with Pb2+, Ag+, Hg22+, Ba2+, Sr2+,
and Ca2+
Chloride salts except compounds           Soluble
with Ag+, Pb2+, and Hg22+

Carbonates, Phosphates,              Most are insoluble
chromates, sulfides, and
hydroxides
Homework 11.3
n Section Assessment page 344 (#30-35)
n Review Worksheet
n Review how to write and balance chemical 
  equations.

								
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