SCH3U
May 2015
Stoichiometry: Mole to Mole Questions
1.
Fe2O3
Mole Ratio
1
:
+
3CO
3

2Fe
:
2
+
:
3CO2
3
+
:
4H2O
4
a) 1.4 moles Fe2O3 will react with how many moles of CO?
3x1.4 = 4.2 mol
Explanation: 1:3 ratio  will require 3x the amount of Fe2O3 for CO
b) How many moles of Fe are produced if 1.6 moles of CO are reacted?
1.6 x 2 = 1.1 mol
3
Explanation:
3 CO = 1.6
2Fe
x
Cross multiple:
3x = 2 x 1.6
Solve:
x = 2 x 1.6
3
X = 1.1
c) How many moles of CO2 are produced if 6.7 moles of CO are used?
2.
C3H8
Mole Ratio
1
:
+
5O2
5

3CO2
:
3
a) How many moles of oxygen are required to react with 3.0 mol of propane (C 3H8)?
3.0 x 5 = 15 mol
Explanation: O2 must be 5x that of propane (5:1 ratio)
b) How many moles of carbon dioxide will be formed from 11.6 mol of oxygen?
11.6 x 3 = 6.96 mol
5
Explanation:
5 O2 = 11.6
3 CO2
x
Cross multiple: 5x = 3 x 11.6
Solve:
x = 3 x 11.6
5
X = 6.96
c) When 1.2 mol of carbon dioxide are formed, how many moles of water are also formed?
1.2x4 = 1.6mol
3
Explanation:
4 H 2O = x
3 CO2
1.2
Cross multiple: 3x = 4 x 1.2
Solve:
x = 4 x 1.2
3
X = 1.6
d) If 50.0 mol of oxygen are available, what is the maximum number of moles of propane that can be
burned?
50.0 = 10.0 mol
5
Explanation: oxygen is always 5 x greater than propane
e) If 200.0 mol of propane and 200.0 mol of oxygen are available, how many moles of each will be
used? 40.0 mol propane and 200.0 mol oxygen
Explanation: again, oxygen is always 5 x greater than propane. We can’t multiply the propane by 5 to
get 1000 mol of oxygen since we only have 200.0 mol, therefore we must divide the oxygen by 5 to
get 40.0 mol of propane
3.
2C8H18
Mole Ratio
2
:
+
25O2
25

16CO2
:
16
+
:
18H2O
18
If 2.2 mol of CO2 are produced from burning octane (C8H18),
a) How many moles of octane have burned?
2.2 = 0.28 mol
8
Explanation: 2: 16 ratio is the same as 1:8 ratio, therefore octane is one eighth of carbon
dioxide
OR
Explanation:
Cross multiple:
Solve:
2 C3H8 = x
16 CO2
2.2
16x = 2 x 2.2
x = 2 x 2.2
16
X = 0.28
b) how many moles of water are produced at the same time?
2.2 x 18 = 2.5 mol
16
Explanation:
18 H2O = x
16 CO2
2.2
Cross multiple: 16x = 18 x 2.2
Solve:
x = 18 x 2.2
16
X = 2.5