CHE 140/170 Handout – The Roadmap meets Stoichiometry
The Roadmap meets Stoichiometry
Our lovely roadmap has returned once more and it’s grown so we can do stoichiometry! It
still converts between grams and moles. But, now we can convert between moles of one
compound to moles of another compound using the balanced chemical equation! Fill in what we
need on the paths below.
grams
grams
moles
moles
s
Okay, now that that’s done that. Let’s try a problem!
Glucose reacts with oxygen to give carbon dioxide and water according to the equation
below. What mass of oxygen (in grams) is required for the complete reaction of 25.0 grams of
glucose?
C6H12O6(s) + 6 O2(g) → 6 CO2(g) + 6 H2O(ℓ)
What do we do now? Let’s follow our steps!
Step 1) Write a balanced chemical reaction.
Step 2) Write down what we know underneath the equation.
Step 3) Write down what we want to know (with units) underneath the question.
Step 4) Use the roadmap to solve the problem!
Step 1)
C6H12O6(s) + 6 O2(g) → 6 CO2(g) + 6 H2O(ℓ)
Steps 2 & 3)
25.0 g
?g
Step 4)
Let’s put our information right on the roadmap!
25.0 g
C6H12O6
? g O2
MM
moles
MM
mol:mol factors from
balanced equation
moles
s
Now, let’s follow our roadmap to get the answer. Remember you can do as one calculation (as
shown below) or three separate ones. If you do as three separates, do not round until the end by
keeping all the numbers in your calculator.
25.0 g C6 H12O 6 
1 mol C6 H12O 6
6 mol O 2
32.00 g O 2


 26.6 g O 2
180.16 g C6 H12O 6 1 mol C 6 H12O 6 1 mol O 2
Now it’s your turn! Answer the following questions.
Roadmap meets Stoichiometry key.docx
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CHE 140/170 Handout – The Roadmap meets Stoichiometry
1. Some metal halides react with water to produce the metal oxide and the appropriate hydrogen
halide.
a. In the reaction below, if you begin with 14.0 mL of TiCl4 (density 1.73 g/mL), what mass
of water is required for a complete reaction?
TiCl4(ℓ) + 2 H2O(ℓ) → TiO2(s) + 4 HCl(g)
14.0 mL
14.0 mL TiCl 4 
?g
1.73 g TiCl 4 1 mol TiCl 4
2 mol H 2 O 18.02 g H 2 O



 4.60 g H 2 O
1 mL TiCl 4 189.7 g TiCl 4 1 mol TiCl 4 1 mol H 2 O
b. Under these same conditions, what mass of TiO2 can be made?
TiCl4(ℓ) + 2 H2O(ℓ) → TiO2(s) + 4 HCl(g)
?g
14.0 mL
14.0 mL TiCl 4 
1.73 g TiCl 4 1 mol TiCl 4
1 mol TiO 2 79.87 g TiO 2



 10.2 g TiO 2
1 mL TiCl 4 189.7 g TiCl 4 1 mol TiCl 4 1 mol TiO 2
2. Sodium azide, the explosive chemical used in automobile airbags, is made by the reaction
below.
a. How many grams of NaN3 can be produced if we start with 15.0 g NaNO3?
NaNO3 + 3 NaNH2 → NaN3 + 3 NaOH + NH3
?g
15.0 g
15.0 g NaNO3 
1 mol NaNO3
1 mol NaN 3 65.01 g NaN 3


 11.5 g NaN 3
84.99 g NaNO3 1 mol NaNO3 1 mol NaN 3
b. How many grams of NaN3 can be produced if we start with 15.0 g NaNH2?
NaNO3 + 3 NaNH2 → NaN3 + 3 NaOH + NH3
15.0 g
15.0 g NaNH2 
?g
1 mol NaN 3 65.01 g NaN 3
1 mol NaNH2


 8.33 g NaN 3
39.01 g NaNH2 3 mol NaNH2 1 mol NaN 3
3. Copper(I) sulfide reacts with oxygen upon heating to give copper metal and sulfur dioxide
gas. What mass of copper metal can be obtained from exactly 500 grams of copper(I)
sulfide?
Cu2S(s) + O2(g) → 2 Cu(s) + SO2(g)
500 g
500 g Cu 2S 
?g
1 mol Cu 2S
2 mol Cu 63.55 g Cu


 399 g Cu
159.2 g Cu 2S 1 mol Cu 2S 1 mol Cu
Roadmap meets Stoichiometry key.docx
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