Transcript 342REDOXQUESTIONS_FROM_REVIEW

Redox #’s 1-5
#1) The reaction absorbs energy, therefore it
is electrolytic (A).
#3) Electrolysis requires an external power
source (A).
#4) Reduction occurs at the cathode and the
positive ion will migrate towards the
negatively charged electrode (A).
#5) AN OX → RED CAT
(D)-oxidation at anode.
#6) Electrolysis, negative electrode →
cathode → Reduction → Gain of e-’s
NaCl(aq) → Na+ + Cl(D)
Cl0 → Cl- + 1e#7) From the reaction
Pb0 + Cu+2 → Pb2+ + Cu0
The lead (Pb) is oxidized (anode) and the
copper is reduced (cathode). FATCATFlow from anode to cathode. OR Pb(s) to
Cu(s)
Formation of Aluminum Oxide
#8)
a.
4 Al0 → Al3+ + 3e3 4e- + O20 → O-2
OR 4Al0 → 4Al3+ +12eOR 3O20 + 12e- → 6O2-
b. The oxidation # in Al2O3 is -2.
Zinc Chromium Electrochemical Cell
Increase in
oxidation # means
Oxidation.
2e- lost
3 Zn0 + 2Cr3+ → 3 Zn2+ + 2 Cr0
3e- gained
3 Zn0 → Zn2++ 2e2 3e- + Cr3+ → Cr0
A reduction
(dec.) in
oxidation #
means
umm…..
OR 3Zn0 → 3Zn2+ +6eOR 2Cr3+ + 6e- → 2Cr0
Problems 9-14
#9)
Cr3+ + 3e- → Cr0
#10) The Cr3+ gains electrons
The Zn0 loses electrons
#11) Nothing happens to the PROTONS, redox is
the loss/gain of ELECTRONS ONLY!!!
#12) RED CAT – Reduction
#13)
#14)
Zn0 → Zn2+ + 2e3Zn0 + 2Cr3+ → 3Zn2+ + 2Cr0
#15
ELECTROLYSIS
D.C. SOURCE
(BATTERY)
The fork to be
electroplated
1e+
Ag
THE ANODE IS SOLID
SILVER, THE SOURCE
OF SILVER IN THIS
REACTION.
+
Ag0
+
Ag1+
0
-Ag
- -
Ag1+ - 1e-
The fork is the cathode because: (A)
1. It is the negative electrode in electroplating
2. It is the site where the silver ions are reduced to
make a layer of solid silver (Ag+1 + 1e- →Ag0)
#17 & 18
Zinc/Copper
Cell
VOLTMETER
SO4
SO4
2-
2-
Na+
Na+
SO42Na+ Na+
2e-
-
Zn
Zn
2eZn2+
SO42-
Zn0(s)  2e- + Zn2+
ANODE (ANOX)
#17) B
A→F →E →D
#18) D
Ions move
through salt
bridge
Cu2+ Cu
Na+ Na+
Cu
Cu2+
SO42-
+
+
+
Cu
2e- + Cu2+  Cu0(s)
CATHODE (REDCAT)
19. (D) electrolytic cells use an applied energy
source.
20. Electrons flow from anode to cathode, identify
which metal is oxidized using Table J.
21. The function of the salt bridge is to transfer
ions and maintain charge.
22. Zn0 → Zn2+ + 2e23. (A) cathode at B
24. Cl- ion will be attracted to the positive
electrode and oxidized there.
25. Zn0 + 2Ag+ → Zn+2 + 2Ag0
(D) The concentration of Zn+2 increases.