Name: __________________ Hour: ________ Date:______
Stoichiometry
If your "given" is
in moles:
If your "given" is in
grams:
Determine the molar ratio
to change from moles of
your original substance to
moles of the desired
substance
If you want your
answer in grams: use
the molar mass of the
desired substance to
convert from moles
back to grams
Use the molar mass of
the compound to
determine the number
of moles
If you want
your
answer in
moles: You
are done!
Determine the molar ratio to
change from moles of your
original substance to moles of
the desired substance
If you want your
answer in moles:
You are done!
If you want your answer
in grams: use the molar
mass of the desired
substance to convert
from moles back to
grams
Class Examples:
MOLEMOLE: Using the reaction
2C(s) + O2(g)  2CO(g)
How many moles of CO are produced from the reaction of 2.50 mol of O2 with an excess of C?
Want
2.5 mol O2 x 2 mol CO
1 mol O2
Given
2.5 mol O2 x 2 mol CO = 2.5 x 2 mol CO = 5 mol CO
1 mol O2
1
MOLEGRAMS: Using the reaction
2C(s) + O2(g)  2CO(g)
How many grams of C are used in the reaction to form 3.00 moles CO?
3.0 mol CO x 2 mol C x 12 g C = 3 x 2 x 12g C = 36 g C
2 mol CO 1 mol C 2 x 1
GRAMSMOLES: Using the reaction
2C(s) + O2(g)  2CO(g)
How many moles of C are used in the reaction to form 30.1 grams CO?
30.1 g CO x 1 mol CO x 2 mol C = 30.1 x 1 x 2 mol C = 1.075 mol C
28 g CO 2 mol CO 28 x 2
GRAMSGRAMS: Using the reaction
2C(s) + O2(g)  2CO(g)
How many grams of C are used in the reaction to form 9.8 grams CO?
9.8 g CO x 1 mol CO x 2 mol C x 12 g C = 9.8 x 1 x 2 x 12 g C = 4.2 g C
28 g CO
2 mol CO 1 mol C
28 x 2 x 1
Practice Problems Note: the formula ratio is in blue for each problem
1.
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?
MOLAR MASS CALCULATION:
NaOH
Na2SO4
2 NaOH + H2SO4  2 H2O + Na2SO4
Na:
1
x
23
=
23
Na: 2 x 23 = 46
200 g NaOH x 1 mol NaOH x 1 mol Na2SO4 x 142 g Na2SO4 = 355 g Na2SO4
O: 1 x 16 = 16
S: 1 x 32 = 32
40 g NaOH 2 mol NaOH 1 mol Na2SO4
H: 1 x 1 = 1
O: 4 x 16 = 64
40
2.
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?
Pb(SO4)2 + 4 LiNO3  Pb(NO3)4 + 2 Li2SO4 MOLAR MASS CALCULATION:
250 g Li2SO4 x 1 mol Li2SO4 x 4 mol LiNO3 x 69 g LiNO3 = 313.64 g LiNO3
110 g Li2SO4 2 mol Li2SO4 1 mol LiNO3
3.
Li2SO4
Li: 2 x 7 = 14
S: 1 x 32 = 32
O: 4 x 16 = 64
110
LiNO3
Li: 1 x 7 = 7
N: 1 x 14 = 14
O: 3 x 16 = 48
69
How many grams of calcium carbonate are required to prepare 50.0 g of calcium oxide?
CaCO3  CaO + CO2
MOLAR MASS CALCULATION:
50.0 g CaO x 1 mol CaO x 1 mol CaCO3 x 100 g CaCO3 = 89.29 g CaCO3
56 g CaO
1 mol CaO
1 mol CaCO3
4.
142
CaO
Ca: 1 x 40 = 40
O: 1 x 16 = 16
56
CaCO3
Ca:1 x 40 = 40
C: 1 x 12 = 12
O: 3 x 16 = 48
100
If 75.0 g of copper react with mercuric nitrate, how many grams of mercury form?
Cu + Hg(NO3)2  Cu(NO3)2 + Hg
MOLAR MASS CALCULATION:
Cu: 64
75.0 g Cu x 1 mol Cu x 1 mol Hg x 201 g Hg = 235.55 g Hg
64 g Cu 1 mol Cu 1 mol Hg
Hg: 201
5.
How many moles of HCl are needed to form 350 moles of Cl2?
4HCl + O2  2H2O + 2Cl2
350 mol Cl2 x 4 mol HCl = 700 mol HCl
2 mol Cl2
6.
How many moles of Na2SO4 is produced when sulfuric acid reacts with 200.0 g of sodium chloride?
2NaCl + H2SO4  2HCl + Na2SO4
MOLAR MASS CALCULATION:
NaCl
Na: 1 x 23 = 23
Cl: 1 x 35 = 35
58
200.0 g NaCl x 1 mol NaCl x 1 mol Na2SO4 = 1.72 mol Na2SO4
58 g NaCl 2 mol NaCl
7.
Na2SO4
Na: 2 x 23 = 46
S: 1 x 32 = 32
O: 4 x 16 = 64
142
How many moles of O2 can be produced by letting 12.00 moles of KClO3 react?
2 KClO3 ---> 2 KCl + 3 O2
12.0 mol KClO3 x 3 mol O2
= 18 mol O2
2 mol KClO3
8.
How many moles of Cu are needed to react with 3.50 moles of AgNO3?
Cu + 2 AgNO3 ---> Cu(NO3)2 + 2 Ag
3.5 mol AgNO3 x 1 mol Cu
= 1.75 mol Cu
2 mol AgNO3
9.
The average human requires 120.0 grams of glucose (C6H12O6) per day. How many grams of CO2 (in the
photosynthesis reaction) are required for this amount of glucose? The photosynthetic reaction is: 6 CO2 +
6 H2O  C6H12O6 + 6 O2
MOLAR MASS CALCULATION:
C6H12O6
CO2
120 g C6H12O6 x 1 mol C6H12O6 x 6 mol CO2 x 44 g CO2 = 176 g CO2
C: 6 x 12 = 72
C: 1 x 12 = 12
180 g C6H12O6 1 mol C6H12O6 1 mol CO2
H: 12 x 1 = 12
O: 2 x 16 = 32
O: 6 x 16 = 96
44
180
10. 12.00 moles of NaClO3 will produce how many grams of O2?
2 NaClO3  2 NaCl + 3 O2
12.00 mol NaClO3 x 3 mol O2 x 32 g O2 = 576 g O2
2 mol NaClO3 1 mol O2
MOLAR MASS CALCULATION:
O2
O: 2 x 16 = 32