HS Chemistry POGIL Activity Topic: Stoichiometry
Basic Stoichiometry
Why? In this activity we will address the question:
How do I convert between different chemical species in a given reaction?
Model 1
2A + 3B → 5C + 4D
2 mol A produces 5 mol C 4 mol A produces 10 mol C
3 mol B produces 4 mol D 6 mol B produces 8 mol D
2 mol A reacts with 3 mol B 6 mol A reacts with 9 mol B
1. What do the coefficients of a balanced equation represent?
2. If 6 mol A are reacted, how many mol D are formed? Explain as a group how you calculated this
answer and show your work.
3. If 15 mol B are reacted, how many mol C are formed? Make sure to show your work.
4. If 8 mol of A are reacted, how many mol B are used? Make sure to show the calculation.
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Basic Stoichiometry
Model 2
2A + 3B → 5C + 4D
If 3 mol A react, how many mol C are produced?
3 mol A * 5 mol C = 7.5 mol C
2 mol A
5. If 21.0 mol A are reacted, how many mol C are produced? Using dimensional analysis, show
how you calculated your answer.
6. If 21.0 mol B are reacted, how many mol A must have reacted?
7. If 0.013 mol D are produced, how many mol C are produced?
8. Discuss as a group and define “stoichiometry” in your own terms. Put your definitions on the
board. We will discuss these definitions as a class.
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Basic Stoichiometry
Model 3
Given the following equation:
_____ N2 (g) + _____ H2 (g) → _____ NH3 (g)
9. If 0.052 mol N2 are reacted, how many mol NH3 are formed? Using dimensional analysis, show
how you calculated your answer.
10. If 0.052 mol N2 are reacted, how many mol H2 are used?
11. If 0.863 mol NH3 are produced, how many mol N2 must have reacted? How many mol H2 must
have reacted?
12. Discuss as a group and list the molar equivalents for N2 + H2 → NH3 based on Model 1.
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Basic Stoichiometry
*** Stop here for Class Discussion ***
Model 4
13. Using complete sentences and working as a group, compare the new mole map in Model 4 to the
original mole map on your cheat sheet.
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Basic Stoichiometry
_____ H2 (g) + _____ O2 (g) → _____ H2O (g)
14. Given the equation above, determine the number of moles of water produced when 5.2 g O2 are
reacted. Make sure to show the dimensional analysis in your work.
15. How many water molecules are produced when 5.2 g O2 are reacted?
16. How many liters of H2 are used when 5.2 g O2 are reacted at STP?
17. Discuss as a group the process to convert between different chemical species in a given reaction.
Make sure you address how the new mole map can be used in this process. Using complete
sentences, write your conclusions below.
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Basic Stoichiometry
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Basic Stoichiometry
On your own
1. One gallon of gasoline can be considered to contain about 25 moles of octane (C8H18).
Octane burns according to the following equation:
C8H18 (l) + O2 (g) → H2O (l) + CO2 (g)
(a) How many moles of dioxygen gas must be used to burn a gallon of gasoline?
(b) How many moles of carbon dioxide are formed?
(c) How many grams of carbon dioxide are formed?
2. Many statues are made of marble (calcium carbonate). Acid rain contains sulfuric acid,
which reacts with marble according to the following equation:
CaCO3 (s) + H2SO4 (aq) → CO2 (g) + H2O (l) + CaSO4 (aq)
(a) How many moles of marble will be consumed if 5 mol H2SO4 fall onto the statue?
(b) How many liters of CO2 are produced when 12 g marble are reacted at STP?
(c) How many grams of the statue will be consumed if 500 g H2SO4 fall onto the statue?
3. Plants convert carbon dioxide, water, and energy from the sun into sugar (C6H12O6) and
dioxygen in the process of photosynthesis.
sunlight
CO2 (g) + H2O (l) → C6H12O6 (l) + O2 (g)
(a) How many grams of sugar are produced from 1000g (one liter) of water?
(b) How many liters of CO2 are needed to react with one liter of water?
4. Thermite reactions have been used in the past for welding railroad rails, making incendiary
bombs, and igniting solid-fuel rocket motors.
Fe2O3 (s) + Al (s) → Fe (l) + Al2O3 (s)
(a) How many grams of iron (III) oxide will be needed to react in order to form 15.0 g iron?
(b) How many grams of aluminum will be needed to react in order to form 15.0 g iron?
(c) How many grams of aluminum oxide will be formed if 1.63*1023 atoms iron are formed?
5. Calcium cyanamide (CaCN2) is used as a fertilizer. The water in soil react with the fertilizer
to deposit NH3 and CaCO3 into the ground.
CaCN2 (s) + H2O (l) → NH3 (g) + CaCO3 (s)
(a) How many grams of NH3 are deposited into the soil if 250 kg CaCN2 are used?
(b) How many grams of water from the soil must react with 250 kg CaCN2?
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Basic Stoichiometry
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Basic Stoichiometry
Teacher Resources
Prior knowledge needed for this activity:
● concept of a mole
● molecular weight
● dimensional analysis
● balancing equations
● mole map
● basic conversions
Thoughts on presentation of the activity:
● At Critical Thinking Question #9, have students put their definition of stoichiometry on the
board. Point out the important parts of their definitions and clear up any misconceptions.
● Stop after Critical Thinking Question #12 and have a class discussion.
Target Responses for the tasks: (Student pages and target responses are attached)
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Basic Stoichiometry
HS Chemistry POGIL Activity Topic: Stoichiometry
Basic Stoichiometry - KEY
Why? In this activity we will address the question:
How do I convert between different chemical species in a given reaction?
Model 1
2A + 3B → 5C + 4D
2 mol A produces 5 mol C 4 mol A produces 10 mol C
3 mol B produces 4 mol D 6 mol B produces 8 mol D
2 mol A reacts with 3 mol B 6 mol A reacts with 9 mol B
17. What do the coefficients of a balanced equation represent?
Molar equivalents / Moles to compare to other species in the reaction
18. If 6 mol A are reacted, how many mol D are produced? Explain as a group how you calculated
this answer and show your work.
6 mol A * 4 mol D = 12 mol D
2 mol A
19. If 15 mol B are reacted, how many mol C are produced? Make sure to show your work.
15 mol B * 5 mol C = 25 mol C
3 mol B
20. If 8 mol of A are reacted, how many mol B are used? Make sure to show the calculation.
8 mol A * 3 mol B = 12 mol B
2 mol A
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Basic Stoichiometry
Model 2
2A + 3B → 5C + 4D
If 3 mol A react, how many mol C are formed?
3 mol A * 5 mol C = 7.5 mol C
2 mol A
21. If 21.0 mol A are reacted, how many mol C are produced? Using dimensional analysis, show
how you calculated your answer.
21.0 mol A * 5 mol C = 52.5 mol C
2 mol A
22. If 21.0 mol B are reacted, how many mol A must have reacted?
21.0 mol B * 2 mol A = 14 mol A
3 mol B
23. If 0.013 mol D are produced, how many mol C are produced?
0.013 mol D * 5 mol C = 0.0163 mol C
4 mol D
24. Discuss as a group and define “stoichiometry” in your own terms. Put your definitions on the
board. We will discuss these definitions as a class.
Using ratios of the balanced equation coefficients to compare different species in a chemical
reaction
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Basic Stoichiometry
Model 3
Given the following equation:
__1__ N2 (g) + __3__ H2 (g) → __2__ NH3 (g)
25. If 0.052 mol N2 are reacted, how many mol NH3 are formed? Using dimensional analysis, show
how you calculated your answer.
0.052 mol N2 * 2 mol NH3 = 0.104 mol NH3
1 mol N2
26. If 0.052 mol N2 are reacted, how many mol H2 are used?
0.052 mol N2 * 3 mol H2 = 0.156 mol H2
1 mol N2
27. If 0.863 mol NH3 are produced, how many mol N2 must have reacted? How many mol H2 must
have reacted?
0.863 mol NH3 * 1 mol N2 = 0.432 mol N2
2 mol NH3
28. Discuss as a group and list the molar equivalents for N2 + H2 → NH3 based
on Model 1.
1 mol N2 uses 3 mol H2 or 1 mol N2 = 3 mol H2
1 mol N2 produces 2 mol NH3 or 1 mol N2 = 2 mol NH3
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Basic Stoichiometry
3 mol H2 produces 2 mol NH3 or 3 mol H2 = 2 mol NH3
*** Stop here for Class Discussion ***
Model 4
29. Using complete sentences and working as a group, compare the new mole map in Model 4 to the
original mole map on your cheat sheet.
The new mole map is different because it has two chemicals (A & B) and connects these two
chemicals by a molar ratio / molar equivalence.
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Basic Stoichiometry
__2__ H2 (g) + __1__ O2 (g) → __2__ H2O (g)
30. Given the equation above, determine the number of moles of water produced when 5.2 g O2 are
reacted. Make sure to show the dimensional analysis in your work.
5.2 g O2 * 1 mol O2 * 2 mol H2O = 0.325 mol H2O
32 g O2 1 mol O2
31. How many water molecules are produced when 5.2 g O2 are reacted?
5.2 g O2 * 1 mol O2 * 2 mol H2O * 6.02 *1023 molecules H2O = 1.96 * 1023 molecules H2O
32 g O2 1 mol O2 1 mol H2O
32. How many liters of H2 are used when 5.2 grams O2 are reacted at STP?
5.2 g O2 * 1 mol O2 * 2 mol H2 * 2
2.4 L H2 = 7.28 L H2
32 g O2 1 mol O2 1 mol H2
17. Discuss as a group the process to convert between different chemical species in a given reaction.
Make sure you address how the new mole map can be used in this process. Using complete
sentences, write your conclusions below.
Convert what you’re given into moles. Use the coefficients of the balanced equation to make a
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Basic Stoichiometry
mole ratio between moles of given to moles of desired. Convert moles of desired into the units
specified by the problem.
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Basic Stoichiometry
On your own
6. One gallon of gasoline can be considered to contain about 25 moles of octane (C8H18).
Octane burns according to the following equation:
2 C8H18 (l) + 25 O2 (g) → 18 H2O (l) + 16 CO2 (g)
(d) How many moles of dioxygen gas must be used to burn a gallon of gasoline? 312.5 mol O2
(e) How many moles of carbon dioxide are formed? 200 mol CO2
(f) How many grams of carbon dioxide are formed? 8800 g CO2
7. Many statues are made of marble (calcium carbonate). Acid rain contains sulfuric acid,
which reacts with marble according to the following equation:
1 CaCO3 (s) + 1 H2SO4 (aq) → 1 CO2 (g) + 1 H2O (l) + 1 CaSO4 (aq)
(d) How many moles of marble will be consumed if 5 mol H2SO4 fall onto the statue? 5 mol CaCO3
(e) How many liters of CO2 are produced when 12 g marble are reacted at STP? 2.69 L CO2
(f) How many grams of the statue will be consumed if 500 g H2SO4 fall onto the statue?
510 g CaCO3
8. Plants convert carbon dioxide, water, and energy from the sun into sugar (C6H12O6) and
dioxygen in the process of photosynthesis.
sunlight
6 CO2 (g) + 6 H2O (l) → 1 C6H12O6 (l) + 6 O2 (g)
(c) How many grams of sugar are produced from 1000g (one liter) of water? 1667 g C6H12O6
(d) How many liters of CO2 are needed to react with one liter of water? 1244 L H2O
9. Thermite reactions have been used in the past for welding railroad rails, making incendiary
bombs, and igniting solid-fuel rocket motors.
1 Fe2O3 (s) + 2 Al (s) → 2 Fe (l) + 1 Al2O3 (s)
(d) How many grams of iron (III) oxide will be needed to react in order to form 15.0 g iron? 21.4gFe
(e) How many grams of aluminum will be needed to react in order to form 15.0 g iron? 7.2 g Al
(f) How many grams of aluminum oxide will be formed if 1.63*1023 atoms iron are formed?
13.8 g Al2O3
10. Calcium cyanamide (CaCN2) is used as a fertilizer. The water in soil react with the fertilizer
to deposit NH3 and CaCO3 into the ground.
1 CaCN2 (s) + 3 H2O (l) → 2 NH3 (g) + 1 CaCO3 (s)
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Basic Stoichiometry
(a) How many grams of NH3 are deposited into the soil if 250 kg CaCN2 are used? 106250 g NH3
(b) How many grams of water from the soil must react with 250 kg CaCN2? 168750 g H2O
