Transcript 06keyshw

Topic 6
Ions in Aqueous Solutions: Redox Reactions
Keys, Group Work;
Homework Assignments
Group Work Keys
• 6.1 Recognizing
Oxidation/Reduction
• 6.2 Calculating Oxidation
Numbers
• 6.3 Oxidation Numbers to
Predict Redox
Homework
Assignments,
Kotz & Treichel,
Chapter 5: 5.7
Slides 9, 10
Key, Group Work 6.1: Recognizing Redox
Reactions
4 Fe + 3 O2 ---> 2 Fe2O3 Combination Type, Redox
Fe2O3 + 6 HCl ---> 2 FeCl3 + 3 H2O
Double Replacement, Acid/Base, NO REDOX
2 FeCl3 + 3 Na2CO3 ---> Fe2(CO3)3 + 6 NaCl
Double Replacement, Precipitation, NO REDOX
2 FeCl3 ---> 2 Fe + 3 Cl2 Decomposition Type,
Redox
2 C4H10 + 13 O2 ---> 8 CO2 + 10 H2O Combustion,
Redox
Key Group Work 6.2, #1: Ox #’s for CrO3
?
-2
Cr O3
?
-6
Known ox #
Total from formula:
Calculating value of Cr:
(?) + (- 6) =0
(?) = 0 + 6 = +6
+6 -2
CrO3
Key, Group Work 6.2, #2: Ox #’s for CrSO3
ox# from
formula :
SO32-
+2
?
-2
Known ox#
Cr S O3
+2
?
-6
Totals from
formula:
Calculating value of S:
+2 + ? - 6 =0
?=0+6-2=4
+2 +4 -2
CrSO3
Key, Group Work 6.2, #3: Ox #’s, K2Cr2O7
Known ox #
+1
?
-2
K2 Cr2 O7
+2
?
Known
ox#
- 14
Totals from formula:
Calculating total value of Cr:
+2 +? - 14 = 0
? = 0 + 14- 2 = + 12
+12 total / 2 atoms Cr = +6/Cr
+1 +6 -2
K2Cr2O7
Key, Group Work 6.3
Mg(s) + 2H+(aq) -----> Mg2+ (aq) + H2(g)
Mg(s) ox # = 0
Mg2+ (aq) ox# = +2
Mg is oxidized; is reducing agent (gave off e’s)
2H+(aq) ox # = +1
H2(g) ox # = 0
H+ is reduced; is oxidizing agent (accepted e’s)
Key, Group Work 6.3, Continued
CaCO3 (s) + H2SO4 (aq) -----> CaSO4 (aq) + H2O(l) + CO2 (g)
No change in any ox #:
Ca, ox # +2
C, ox # +4
O, ox # -2
S, ox # +6
H, ox # +1
No change in ox #,
No redox
(Double replacement,
exchange type, first
yielding H2CO3)
Key, Group Work 6.3, continued
2 Na (s) + 2 H2O (l) -----> 2Na+ (aq) + OH- (aq) + H2 (g)
2 Na (s) ox # = 0
2Na+ (aq) ox# = +1
Na is oxidized; is reducing agent (gave off e)
2 H2O (l) ox #, H = +1
H2(g) ox # = 0
H+ is reduced; H2O is oxidizing agent (accepted e’s)
Chapter 5: Oxidation - Reduction Reactions
Assignments
Section 5.7
• Study carefully Chapter 5, Sections 5.7, p. 204-212
• Review chapter highlights, p. 228, #10, 11, 12
Memorize:
• summary chart, oxidation numbers, slide 20
Written Assignments, Chapter 5 (5.7)
In Chapter Exercises:
#5.10- 5.12
Chapter 5“study questions” p. 229-231:
12, 54, 56, 58