# Mass to Mass by lanyuehua

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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
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

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
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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