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					Reaction Stochiometry

       Chapter 3
Balancing Reactions
• Law of Conservation of Mass
   – There is no detectable change in quantity of
     matter in an ordinary chemical reaction.

  1. C7H16 burns in oxygen to form carbon dioxide and water
                        
                       
         C7H16 + 11 O2   7 CO2 + 8 H2O

 2. Propane, C3H8 burns in oxygen to form carbon dioxide
 and water

Balancing Reactions

 3. NH3 burns in oxygen to form NO & water
Balance the following reactions:
1) Na + Cl2  NaCl

2) N2 + H2  NH3

3) Fe + O2  Fe2O3

4) Cu + AgNO3  Ag + Cu(NO3)2

5) H2SO4 +     NaCN  HCN + Na2SO4

6)   Fe2O3 +   CO    Fe   + CO2
 Calculations using Chemical Equations
                          
                         
           Fe2 O3 + 3 CO  2 Fe + 3 CO2
 1. How many iron atoms can be produced by the
   reaction of 2.50 x 105 formula units of iron (III)
 oxide with excess carbon monoxide
                                                      2 Fe atoms
  ? Fe atoms = 2.50 10 formula units Fe 2O 3 
                          5

                                                1 formula units Fe 2O 3
   5.00 10 5 Fe atoms
 Calculations using Chemical Equations
                       
                      
        Fe2 O3 + 3 CO  2 Fe + 3 CO2
 2. What mass of CO is required to react with 146 g
   of iron (III) oxide?
                   76.8 g CO

 3. What mass of carbon dioxide can be produced
 by the reaction of 0.540 mole of iron (III) oxide
 with excess carbon monoxide?
                     71.3 g CO2
 Calculations using Chemical Equations
                        
                       
         Fe2 O3 + 3 CO  2 Fe + 3 CO2
 4. What mass of iron (III) oxide reacted with excess
   carbon monoxide if the carbon dioxide produced
 by the reaction had a mass of 8.65 grams?
                     10.5 g Fe2O3

 5. How many pounds of carbon monoxide would
 react with 125 pounds of iron (III) oxide?
                      65.7 lb CO
Calculations using Chemical Equations
Using the following equation:

         NaOH + H2SO4  H2O + Na2SO4

How many grams of sodium sulfate will be formed
 if you start with 200 grams of sodium hydroxide
 and you have an excess of sulfuric acid?

               355 grams of Na2SO4
•
Calculations Using Chemical Equations
Using the following equation:

     Pb(SO4)2 + LiNO3  Pb(NO3)4 + Li2SO4

How many grams of lithium nitrate will be
 needed to make 250 grams of lithium sulfate,
 assuming that you have an adequate amount
 of lead (IV) sulfate to do the reaction?

               313 grams of LiNO3
Limiting Reagent Concept
Calculations: Limiting Reagent
1. What is the maximum mass of sulfur dioxide
  that can be produced by the reaction of 95.6 g
  of carbon disulfide with 110. g of oxygen?

CS2  3 O2  CO2  2 SO2
                    CS2  3 O 2  CO2  2 SO 2
                          1 mol CS2 2 mol SO 2 64.1 g SO 2
? g SO 2  95.6 g CS2                                    161 g SO 2
                            76.2 g   1 mol CS2 1 mol SO 2
                       1 mol O 2 2 mol SO 2 64.1 g SO 2
? g SO 2  110 g O 2                                   147 g SO 2
                       32.0 g O 2 3 mol O 2   1 mol SO 2

•   Which is limiting reactant?
•   Limiting reactant is O2.
•   What is maximum mass of sulfur dioxide?
•   Maximum mass is 147 g.
Calculations: Limiting Reagent
The reaction between aluminum and iron (III)
  oxide can generate temperatures approaching
  3000oC and is used in welding metals:
         2Al + Fe2O3  Al2O3 + 2Fe
In one process, 124g of Al are reacted with 601g
  of Fe2O3. (a) Calculate the mass (g) of Al2O3
  formed. (b) How much of the excess reagent is
  left at the end of the reaction?
               234 grams of Al2O3
               234 grams
3. The depletion of ozone (O3) in the stratosphere
   has been a matter of great concern among
   scientists in recent years. It is believed that
   ozone can react with nitric oxide (NO) that is
   discharged from the high-altitude jet plane, the
   SST. The reaction is
               O3 + NO  O2 + NO2
If 0.740g of O3 reacts with 0.670g of NO, how many
   grams of NO2 will be produced? Which
   compound is the limiting reagent? Calculate the
   number of moles of the excess reagent in this
   reaction.
                    0.709 g of NO2
                          O3
                   6.9x10-3 mol NO
Reaction Yield
• Theoretical Yield
  – Amount of product based on the limiting reagent
  – Assumes all the limiting reagent reacted
• Actual Yield
  – Amount of product obtained from the reaction
  – Experiment
• Percent Yield
                         actual yield
            %yield                      x 100%
                       theoretical yield
Initially, vanadium metal, which is used in steel
  alloys, can be obtained by reacting
  vanadium(V) oxide with calcium at high
  temperatures:
           5Ca + V2O5  5CaO + 2V
In one process, 1.54x103 g of V2O5 react with
  1.96x103 g of Ca. (a) Calculate the theoretical
  yield of V. (b) Calculate the percent yield if
  803 g of V are obtained.
                    863 g V
                    93.0%
Assignment
Chapter 3
# 83, 85, 89, 91

				
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