Documents
Resources
Learning Center
Upload
Plans & pricing Sign in
Sign Out

Stoichiometry

VIEWS: 12 PAGES: 43

									         Chapter 8
Classification of Reactions
      Combustion Reactions
• A combustion reaction is one in which a
  substance rapidly combines with oxygen
  to form one or more oxides.

Hydrocarbon + O2  CO2 + H2O
            Exploding Flour
FLOUR
                      EXPLOSION:
                       Fuel (flour)
        6” PVC Pipe    Ignition (candle)
                       Oxygen (combustion)




                               As confinement increases,
                               EXPLOSION is greater.
 Combustion of a Hydrocarbon

GENERAL FORMULA:          CH + O2  CO2 + H2O

Many homes get heat from propane (C3H8) heaters.

Write a balanced chemical equation for the complete
combustion of propane gas.
      C3H8(g) + O2(g)  CO2(g) + H2O(g)

    C3H8(g) + 5 O2(g)  3 CO2(g) + 4 H2O(g) + energy
Combustion of Alcohol Demo




        Click box to view movie clip.
   Combustion of Hydrocarbon (cont.)

Ideal Stoichiometry

    C3H8(g) + 5 O2(g)  3 CO2(g) + 4 H2O(g) + energy
                           D


Too ‘rich’ (not enough oxygen – too much fuel)

    C3H8(g) + 3 O2(g)            CO (g) + 4 H2O(g) + energy
                            D



    C3H8(g) + 2 O2(g)  3 C (g) + 4 H2O(g)         + energy

                      SOOT
                                                      Combustion of
                                                      Methane Gas




Davis, Metcalfe, Williams, Castka, Modern Chemistry, 1999, page 245
Click box to view movie clip.
                                Combustion of Glucose




Kelter, Carr, Scott, Chemistry A World of Choices 1999, page 130
             Combustion of Iron
 Thermite     Reaction
      underwater welding

Fe2O3 + 2 Al  2 Fe + Al2O3

 Formation     of Rust

       4 Fe + O2  2 Fe2O3
Combustion of Copper

                                      Copper  burns with
                                       a green color
                                      Copper forms a
                                       patina (oxide)
                                          green in color
                                            • CuO2
                                          black in color
 Statue of Liberty is covered with
                                            • CuO
 copper that has oxidized to form
 copper (II) oxide, CuO2.
                 Synthesis Reactions
A + B  AB             or AB + C  ABC
 • Whenever two or more substances combine
   to form a single product, the reaction is called
   a synthesis reaction.


 Click box to view
 movie clip.
       Synthesis Reaction

  Direct combination reaction (Synthesis)

          2 Na    +         Cl2              2 NaCl

           Na               Cl                Na+ Cl -

                            Cl                Cl - Na+
           Na

General form: A         +         B               AB
           element or        element or         compound
           compound          compound
   Decomposition Reactions
• In a decomposition reaction, a compound
  breaks down into two or more simpler
  substances.


             AB  A + B
Decomposition Reaction

 Decomposition reaction
           2 H 2O          2 H2    +      O2

                     H
             O             H H
                    H                    O
                                   +
                     H
             O                           O
                           H H
                 H

 General form: AB           A      +     B
         compound         two or more elements
                            or compounds
Single Replacement Reactions




  A + BC  B + AC
Formation of a solid AgCl




AgNO3(aq) + KCl(aq)  KNO3 (aq) + AgCl(s)
Single and Double Replacement
           Reactions
      Single-replacement reaction

       Mg    +   CuSO4               MgSO4    +       Cu


      General form:
        A       + BC                 AC       +       B



      Double-replacement reaction

       CaCO3     +    2 HCl           CaCl2       +   H2CO3




      General form:
        AB        +   CD              AD          +       CB
Activity Series
                            Element Reactivity
                               Li
                               Rb
                               K
 Foiled again –                Ba
                                      Halogen Reactivity
 Aluminum loses to Copper      Ca
                               Na
                               Mg         F2
                               Al         Cl2
                               Mn         Br2
                               Zn         I2
                               Cr
                               Fe
                               Ni
                               Sn
                               Pb
                               H2
                               Cu
                               Hg
                               Ag
                               Pt
                               Au
Potassium reacts with Water
            POW!
Double Replacement Reactions




      AB + CD  CB + AD

         Driving Forces
Double Replacement Reaction
             Summary of Classes of Reactions

                                                               Chemical reactions



                  Precipitation                                Oxidation-Reduction     Acid-Base
                    reactions                                      Reactions           Reactions



                                                                   Synthesis         Decomposition
                   Combustion                                      reactions           reactions
                    Reactions                                    (Reactants are      (Products are
                                                                   elements.)          elements.)

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 242
      Reactions in Aqueous Solutions

• When aqueous solutions that contain ions
  are mixed, the ions may react in a double-
  replacement reaction.

• The product is typically a solid precipitate,
  water, or a gas.
Table 8.1
Figure
   8.3:
Solubili
 ties of
commo
    n
compo
 unds.
      Reactions in Aqueous Solutions
• An example of a double-replacement reaction
  that produces a precipitate occurs when
  aqueous solutions of sodium chloride and
  silver nitrate are mixed to form a precipitate
  of solid silver chloride.
      Reactions in Aqueous Solutions
• To show all of the particles in solution as
  they really exist, a complete ionic equation
  can be written.


• The sodium and nitrate ions are on both sides
  of the equation.
• Such ions that do not participate in a reaction
  are called spectator ions.
      Reactions in Aqueous Solutions
• An ionic equation that does not show
  spectator ions but only the particles that
  participate in a reaction is called a net
  ionic equation.
• In the case of the reaction above, the net
  ionic equation from which the sodium and
  nitrate ions have been removed is as follows.
      Writing Ionic Equations

• Write the balanced chemical equation for the
  reaction between aqueous solutions of
  strontium nitrate and potassium sulfate, which
  forms the precipitate strontium sulfate.

• Then write the complete ionic and net ionic
  equations.
      Writing Ionic Equations
• Write the correct skeleton equation.



• Use coefficients to produce the balanced
  chemical equation.
      Writing Ionic Equations

• Write the complete ionic equation.
      Writing Ionic Equations

• Cross out the spectator ions, which are those
  that are on both sides of the equation.



• That leaves the net ionic equation.
         Reactions that form water or a gas
•   Some double-replacement reactions in
    aqueous solution produce water or a gas
    (or both) rather than a precipitate.
•   In such cases, the water or gas is shown as
    a product in the net ionic equation, as are
    the ions that produced it.
•   The remaining ions are eliminated as
    spectator ions.
•   The following example problem illustrates
    this concept.
      Reactions that form water or a gas

• When hydrochloric acid and potassium
  hydroxide solutions are mixed, water results,
  together with an aqueous solution of
  potassium chloride.

• Write the balanced chemical equation, a
  complete ionic equation, and a net ionic
  equation for this reaction.
      Reactions that form water or a gas
• The balanced chemical equation is the same
  as the skeleton equation.
      Reactions that form water or a gas
• Write the complete ionic equation, which
  includes all of the ions.


• Remove the spectator ions to produce the net
  ionic equation.
      Question 1
Write a balanced chemical, complete ionic, and
net ionic equations for the following reaction:

  Aqueous solutions of lead(II) nitrate and
  ammonium chloride are mixed, forming a
  precipitate of lead(II) chloride.
  Additional Assessment Questions

Answer
           Chemical:


        Complete Ionic:


            Net ionic:
         Additional Assessment Questions

      Question 2

Write a balanced chemical, complete ionic,
and net ionic equations for the reaction
between the following substances, which
produce water:

  nitric acid (HNO3) and aqueous barium
  hydroxide
          Additional Assessment Questions

      Answer
                   Chemical:

                Complete ionic:

                   Net ionic:

or, with coefficients reduced to lowest terms,
         Additional Assessment Questions

      Question 3
Write a balanced chemical, complete ionic,
and net ionic equations for the reaction
between the following substances, which
produce a gas:

  hydrochloric acid and aqueous sodium
  cyanide, with production of hydrogen
  cyanide gas (HCN)
  Additional Assessment Questions

Answer
           Chemical:

       Complete ionic:

            Net ionic:

								
To top