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					Mass to Mass Stoichiometry

      Honors Chemistry
           Unit 5
  Ex. How many grams of copper (I) sulfide
  could be produced from 7.90 g copper (I)
  chloride reacting with an excess of H2S
  gas?
  Steps to Solve:
1. Write a balanced equation. Determine
  what you start with and what you want to
  know.
           H2S + 2CuCl  Cu2S +2HCl
H2S + 2CuCl  Cu2S +2HCl
2. Convert grams to moles.
    7.90 g CuCl   1mole CuCl = 0.0798 mol CuCl
                  99.0 g CuCl

3. Covert moles of what you start with to moles of
    what you want to know using a mole ratio. You get
    this ratio from the balanced chemical reaction!
    0.0798 mol CuCl 1 mol Cu2S = 0.0399 mol Cu2S
                       2 mol CuCl

4. Convert moles of what you want to know to grams.

    0.0399 mol Cu2S 159.1 g Cu2S = 6.35 g Cu2S
                     1 mol Cu2S
This can also be done all together as
              follows:

7.90 g CuCl   1mole CuCl 1 mole Cu2S 159.1g Cu2S
              99.0 g CuCl 2 moles CuCl 1mole Cu2S
 2NaOH + H2SO4  2H2O + Na2SO4
 How many grams of sodium sulfate will form if you
  start with 200. grams of sodium hydroxide and
  you have an excess of sulfuric acid?

             1 mole      1 mole
200 g NaOH   NaOH        Na2SO4     142.05 g Na2SO4
             40.0 g     2 moles
                                    1 mole Na2SO4
             NaOH       NaOH



        = 355.1 grams Na2SO4
Pb(SO4)2 + 4LiNO3  Pb(NO3)4 + 2Li2SO4
How many grams of lithium nitrate will be needed to
 make 250. grams of lithium sulfate, assuming you
 have enough lead (IV) sulfate to complete the
 reaction?
               1 mole     4 moles    68.95 g
250.g Li2SO4   Li2SO4     LiNO3      LiNO3
               109.95 g   2 moles     1 mole
               Li2SO4     Li2SO4      LiNO3



          = 313.6 grams LiNO3
           Other Examples
2KClO3  2KCl + 3O2
Given 0.0032 moles of KClO3, how many
 grams of KCl will form?

0.0032 moles   2 moles KCl     74.55 g KCl
KClO3
               2 moles KClO3   1 mole KCl


         0.239 grams KCl will form
 2PbS+ 3O2  2PbO + 2SO2
Given 6.64 x 10-3 grams of oxygen, how
 many moles of SO2 will form?


6.64 x 10-3 g O2   1 mole O2   2 moles SO2

                   32.0 g O2    3 moles O2



          = 1.38 x 10-4 moles SO2

				
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