Uploaded by Dr. J. Ulises Reveles

pogil redox Part 1

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NAME: _______________________________
DATE: ______________
AP Chemistry
POGIL: Oxidation and Reduction
Why?
Many of the items you use on a daily basis rely on batteries for power. Most batteries supply electricity through
oxidation-reduction reactions that exchange electrons from one atom to another. Current materials do not always allow
for an efficient transfer of these electrons, so overheating may occur…
PHENOMENA - Cool Light Demonstration
Observations:
Possible Explanation:
Success Criteria
ο‚· Determine the oxidation number for an element in a compound.
ο‚· Separate a reaction into oxidation and reduction into balanced half-reactions.
ο‚· Calculate the electron transfer during a redox reaction.
MODEL 1: Oxidation Numbers
Redox (reduction-oxidation) reactions involve the transfer of one or more electrons from a reductant (reducing agent) to
an oxidant (oxidizing agent). This transfer is complete, and does not need to involve pair of electrons. The best way to
keep track of this transfer is to use a bookkeeping trick called “oxidation numbers”. This assigns each atom of a
compound virtual charges, or electron numbers.
POGIL:
O x i d a t i o n a n d R e d u c t i o n | Page 2
Key Questions
1. For neutral compounds, the sum of all oxidation numbers must equal __________ . For all polyatomic ions, the sum
of all oxidation numbers must equal __________.
a. The sum of all the oxidation numbers for H2O must equal __________.
b. The sum of all the oxidation numbers for 𝑆𝑂42− must equal __________.
2. Show how all the oxidation numbers in KMnO4 obey the rule for neutral compounds.
3.
Why does C have an oxidation number of zero by itself, but +2 in the compound CO?
Exercises
4. Assign oxidation numbers to every element in the following:
Li2O
P4
CaH2
Fe2O3
MnCl3
O2
O3
H2O
H2O2
HO2
OF2
S8
H2
Cs2O2
CH2Cl2
POGIL:
O x i d a t i o n a n d R e d u c t i o n | Page 3
5. Assign oxidation numbers to every element in the following polyatomic ions:
𝐢𝑙𝑂4−
𝑆𝑂42−
𝑃𝑂33−
𝑀𝑛𝑂4−
𝑀𝑛𝑂42−
6. Assign oxidation numbers to every element in the following ternary compounds:
K2TiO3
(NH4)3PO4
Ti(SeO3)2
Na2SO4
Pb(IO4)2
7. Assign oxidation numbers to the atoms in these covalent compounds. You must take into account the atoms
bonded to each carbon.
Ethanol
Model 2: Exchange of Electrons
Acetic Acid
POGIL:
O x i d a t i o n a n d R e d u c t i o n | Page 4
Redox Reactions
2+
2+
A. 𝑍𝑛(𝑠) + 𝐢𝑒(π‘Žπ‘ž)
→ 𝑍𝑛(π‘Žπ‘ž)
+ 𝐢𝑒(𝑠)
−
2−
2−
B. 2𝐼(π‘Žπ‘ž)
+ 𝑆2 𝑂8(π‘Žπ‘ž)
→ 𝐼2(π‘Žπ‘ž) + 2𝑆𝑂4(π‘Žπ‘ž)
C. 4𝐹𝑒(𝑠) + 3𝑂2(𝑔) → 2𝐹𝑒2 𝑂3(𝑠)
+
−
2+
3+
D. 4𝐻(π‘Žπ‘ž)
+ 𝑀𝑛𝑂4(π‘Žπ‘ž)
+ 3𝐹𝑒(π‘Žπ‘ž)
→ 3𝐹𝑒(π‘Žπ‘ž)
+ 𝑀𝑛𝑂2(π‘Žπ‘ž) + 2𝐻2 𝑂(𝑙)
Non-Redox Reactions
+
−
E. 𝐻𝐢𝑙(𝑔) + 𝐻2 𝑂(𝑙) → 𝐻3 𝑂(π‘Žπ‘ž)
+ 𝐢𝑙(π‘Žπ‘ž)
F. 2π‘π‘Žπ‘‚π»(π‘Žπ‘ž) + 𝐻2 𝑆𝑂4(π‘Žπ‘ž) → π‘π‘Ž2 𝑆𝑂4(π‘Žπ‘ž) + 2𝐻2 𝑂(𝑙)
2+
−
G. π΅π‘Ž(π‘Žπ‘ž)
+ 2𝑂𝐻(π‘Žπ‘ž)
→ π΅π‘Ž(𝑂𝐻)2(𝑠)
H. 2𝐴𝑔𝑁𝑂3(π‘Žπ‘ž) + πΆπ‘ŽπΆπ‘™2(π‘Žπ‘ž) → πΆπ‘Ž(𝑁𝑂3 )2(π‘Žπ‘ž) + 2𝐴𝑔𝐢𝑙(𝑠)
Key Questions
8. What two types of reactions are shown in the model?
9. Examine the redox and non-redox reactions. Is/are there any feature(s) in the redox reactions that would allow you
to identify them as redox reactions? If yes, use specific examples from the model to support your answer.
10. In the space under each reaction in the model, write the oxidation number for every atom. An example is shown:
4𝐹𝑒(𝑠)
0
+
3𝑂2(𝑔)
0
0
οƒ 
2𝐹𝑒2 𝑂3
+3 -2
+3 -2
-2
POGIL:
O x i d a t i o n a n d R e d u c t i o n | Page 5
11. Identify any elements that changed oxidation number in the reactions in the model. Connect the starting and
ending oxidation numbers with a line. An example is shown.
4𝐹𝑒(𝑠)
+
0
3𝑂2(𝑔)
0
0
οƒ 
2𝐹𝑒2 𝑂3
+3 -2
+3 -2
-2
12. Based on the oxidation number analysis you just performed, are there any features of the redox reactions that
would allow you to identify them? Use specific examples to support your answer.
13. Identify the following reactions as either redox or non-redox using oxidation numbers as evidence.
a. 𝑃𝑏(𝑁𝑂3 )2(π‘Žπ‘ž) + 2π‘π‘ŽπΌ(π‘Žπ‘ž) → 𝑃𝑏𝐼2(𝑠) + 2π‘π‘Žπ‘π‘‚3(π‘Žπ‘ž)
b. 2𝐻2 𝑂(𝑔) → 2𝐻2(𝑔) + 𝑂2(𝑔)
c. 𝐢𝐻4(𝑔) + 2𝑂2(𝑔) → 2𝐻2 𝑂(𝑔) + 𝐢𝑂2(𝑔)
d. 𝐻𝐢𝑙(π‘Žπ‘ž) + π‘π‘Žπ‘‚π»(π‘Žπ‘ž) → 𝐻2 𝑂(𝑙) + π‘π‘ŽπΆπ‘™(π‘Žπ‘ž)
MODEL 3: Single Replacement Reactions
Back in first year chemistry, you did a lab where you placed metal pieces in solutions with other metal cations. When
you place the copper metal in the silver solution, the metal turned gray and the solution went from clear and colorless
to a light blue. When you place the copper metal in a solution with zinc ions, nothing happened. From this data, you
were able to determine the relative reactivity of the metals.
POGIL:
O x i d a t i o n a n d R e d u c t i o n | Page 6
Suppose you have the following metals and corresponding solutions to perform similar reactions: Al(s) and Al(NO3)3(aq);
Pb(s) and Pb(NO3)2(aq); Ni(s) and Ni(NO3)2(aq); and Ag(s) and AgNO3(aq). The results are as follows.
2+
3+
2𝐴𝑙(𝑠) + 3𝑃𝑏(π‘Žπ‘ž)
→ 2𝐴𝑙(π‘Žπ‘ž)
+ 3𝑃𝑏(𝑠)
2+
3+
2𝐴𝑙(𝑠) + 3𝑁𝑖(π‘Žπ‘ž) → 2𝐴𝑙(π‘Žπ‘ž) + 3𝑁𝑖(𝑠)
+
3+
𝐴𝑙(𝑠) + 3𝐴𝑔(π‘Žπ‘ž)
→ 𝐴𝑙(π‘Žπ‘ž)
+ 3𝐴𝑔(𝑠)
3+
𝑁𝑖(𝑠) + 𝐴𝑙(π‘Žπ‘ž)
→ 𝑁𝑅
2+
2+
𝑁𝑖(𝑠) + 𝑃𝑏(π‘Žπ‘ž) → 𝑁𝑖(π‘Žπ‘ž)
+ 𝑃𝑏(𝑠)
+
2+
𝑁𝑖(𝑠) + 2𝐴𝑔(π‘Žπ‘ž) → 𝑁𝑖(π‘Žπ‘ž) + 2𝐴𝑔(𝑠)
3+
𝑃𝑏(𝑠) + 𝐴𝑙(π‘Žπ‘ž)
→ 𝑁𝑅
2+
𝑃𝑏(𝑠) + 𝑁𝑖(π‘Žπ‘ž) → 𝑁𝑅
+
2+
𝑃𝑏(𝑠) + 2𝐴𝑔(π‘Žπ‘ž)
→ 𝑃𝑏(π‘Žπ‘ž)
+ 2𝐴𝑔(𝑠)
3+
𝐴𝑔(𝑠) + 𝐴𝑙(π‘Žπ‘ž)
→ 𝑁𝑅
2+
𝐴𝑔(𝑠) + 𝑃𝑏(π‘Žπ‘ž) → 𝑁𝑅
2+
𝐴𝑔(𝑠) + 𝑁𝑖(π‘Žπ‘ž)
→ 𝑁𝑅
14. Rank Al, Pb, Ni, and Ag from most reactive to least reactive. ______ > ______ > ______ > ______
15. Refer to your copy of the Activity Series for Metals. Find Al, Pb, Ni, and Ag. How does the positon of the metal
relate to its chemical reactivity?
16. If a strip of zinc metal is added to an aqueous solution of copper(II) sulfate, over time one will notice that a brown
precipitate accumulates on the strip of metal and that the solution becomes progressively less blue in color. Using
the Activity Series, explain what chemical reaction is occurring and write a balanced net ionic equation for the
2+
reaction between 𝑍𝑛(𝑠) and 𝐢𝑒(π‘Žπ‘ž)
.
17. Hydrogen is often written on the Periodic Table in Group IA (Group 1), because the chemical reactivity of hydrogen
cations often resembles that of the cations of the alkali metals. In elemental form, hydrogen exists as a diatomic gas
(𝐻2(𝑔) ). Use the Activity Series to explain the following.
a. Explain why the following occurs when calcium is added to water: πΆπ‘Ž(𝑠) + 2𝐻2 𝑂(𝑙) → πΆπ‘Ž(𝑂𝐻)2(π‘Žπ‘ž) + 𝐻2(𝑔)
b. Explain why zinc metal dissolves in hydrochloric acid: 𝑍𝑛(𝑠) + 2𝐻𝐢𝑙(π‘Žπ‘ž) → 𝑍𝑛𝐢𝑙2(π‘Žπ‘ž) + 𝐻2(𝑔)
c. Explain why copper metal does not dissolve in hydrochloric acid.
POGIL:
O x i d a t i o n a n d R e d u c t i o n | Page 7
MODEL 4: Half reactions
The process of oxidation and reduction can be thought of as a transfer of electrons from one atom to another. As a
result of this process, the oxidation numbers of both atoms change. All redox reactions can be divided up into two
reactions: an oxidation half-reaction and a reduction half-reaction. This allows for better understanding of the electron
transfer process.
A OVERALL
OX
RED
B OVERALL
OX
RED
C OVERALL
OX
RED
D OVERALL
OX
RED
2+
2+
𝑍𝑛(𝑠) + 𝐢𝑒(π‘Žπ‘ž)
→ 𝑍𝑛(π‘Žπ‘ž)
+ 𝐢𝑒(𝑠)
2+
−
𝑍𝑛 → 𝑍𝑛 + 2𝑒
𝐢𝑒2+ + 2𝑒 − → 𝐢𝑒
−
2−
2−
2𝐼(π‘Žπ‘ž)
+ 𝑆2 𝑂8(π‘Žπ‘ž)
→ 𝐼2(π‘Žπ‘ž) + 2𝑆𝑂4(π‘Žπ‘ž)
2𝐼 − → 𝐼2 + 2𝑒 −
𝑆8 𝑂82− + 2𝑒 − → 2𝑆𝑂42−
4𝐹𝑒(𝑠) + 3𝑂2(𝑔) → 2𝐹𝑒2 𝑂3(𝑠)
𝐹𝑒 → 𝐹𝑒 3+ + 3𝑒 −
𝑂2 + 4𝑒 − → 2𝑂2−
+
−
2+
3+
4𝐻(π‘Žπ‘ž)
+ 𝑀𝑛𝑂4(π‘Žπ‘ž)
+ 3𝐹𝑒(π‘Žπ‘ž)
→ 3𝐹𝑒(π‘Žπ‘ž)
+ 𝑀𝑛𝑂2(π‘Žπ‘ž) + 2𝐻2 𝑂(𝑙)
2+
3+
−
𝐹𝑒 → 𝐹𝑒 + 𝑒
+
4𝐻 + 𝑀𝑛𝑂4− + 3𝑒 − → 𝑀𝑛𝑂2 + 2𝐻2 𝑂
Key Questions
18. What does the “e-“ symbol represent in the half-reactions?
19. Looking at the oxidation half-reactions:
a. Which of the following types of particles may undergo oxidation? (Circle all that apply.)
Neutral Atoms/Molecules
Cations
Anions
b. Are electrons lost or gained by the atom during the process of oxidation?
c. The oxidation number of the atom being oxidized ( Increases / Decreases ).
20. Looking at the reduction half-reactions:
a. Which of the following types of particles may undergo oxidation? (Circle all that apply.)
Neutral Atoms/Molecules
Cations
Anions
b. Are electrons lost or gained by the atom during the process of reduction?
c. The oxidation number of the atom being reduced ( Increases / Decreases ).
21. In a redox reaction, the oxidizer takes the electrons, so it is is the atom being ( oxidized / reduced ). The reducer is
the atom losing the electrons, so it is the atom being ( oxidized / reduced ).
POGIL:
O x i d a t i o n a n d R e d u c t i o n | Page 8
Read This!
To remember which process is which, remember the phrase “LEO the lion goes GER.”
LEO = Loss of Electrons is Oxidation
GER = Gain of Electrons is Reduction
22. Consider the incomplete half-reactions:
a. Use oxidation numbers to identify the reactions below as oxidation or reduction.
b. Place the correct number of electrons on the appropriate side of the reaction to balance the equation charges.
𝐼2 → 2𝐼 −
πΆπ‘Ÿ 2+ → πΆπ‘Ÿ 3+
𝐢𝑙𝑂2− + 𝐻2 𝑂 → 𝐢𝑙𝑂3− + 2𝐻 +
π‘†π‘Ÿ → π‘†π‘Ÿ 2+
23. Show that the two half reactions for Reaction A can be added together to give the overall redox reaction.
A OVERALL
OX
RED
2+
2+
𝑍𝑛(𝑠) + 𝐢𝑒(π‘Žπ‘ž)
→ 𝑍𝑛(π‘Žπ‘ž)
+ 𝐢𝑒(𝑠)
2+
−
𝑍𝑛 → 𝑍𝑛 + 2𝑒
𝐢𝑒2+ + 2𝑒 − → 𝐢𝑒
24. What happens when you try to add together the half reactions for C?
C OVERALL
OX
RED
25. How would you remedy the issue found in #24?
4𝐹𝑒(𝑠) + 3𝑂2(𝑔) → 2𝐹𝑒2 𝑂3(𝑠)
𝐹𝑒 → 𝐹𝑒 3+ + 3𝑒 −
𝑂2 + 4𝑒 − → 2𝑂2−
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