A Getting-It-On Review and Self-Test
Redox and Electrochemistry
Material which gains electrons is said to be (1)
while material
which loses electrons is said to be (2)
. Oxidation is a
(3)
in oxidation number and reduction is a (4)
in
oxidation number.
Electric current in primary or (5)
conductors is the flow of
(6)
.
Electrolysis occurs in (7)
cells which require an applied
(8)
. Voltaic cells are (9)
and electrolytic
are (10)
. Both cells involve movement of current via
(11)
flow in the primary conductor and (12)
flow in the
secondary conductor. Regardless of cell type, (13)
occurs at the anode and (14)
occurs at the cathode.
15.
Balance this equation after answering some questions below about
it.
H2O2 +
KMnO4 +
a.
b.
16.
H2SO4 →
MnSO4 +
H2O +
O2 +
K2SO4
What is the oxidation number of Mn in KMnO4 and MnSO4?
What is the oxidation number of O in H2O2 and O2?
Determine the oxidation number of the underlined elements:
PO3─3
H3AsO4
NaH
Ba(ClO2)2
KBrO4
C2H6
NaHCO3
2
17.
Label the electrolytic cell below in terms of 1° and 2° conductors,
cathode, anode, electrolytic solution, and direction of ion flow:
e─
battery
M
A─
18.
Balance the following equations:
a.
HCl + H3MoO4 →
b.
Cl2 + KBr →
c.
Zn + H3AsO4 + HCl →
ZnCl2 + AsH3 + H2O
d.
CoS + HNO3 + HCl →
CoCl2 + NO2 + H2SO4 + H2O
e.
Zn + HNO3 →
f.
H2O2 + FeCl2 + HCl →
g.
Na2C2O2 + H2Cr2O7 + HCl →
Mo2O3 + Cl2 + H2O
KCl + Br2
Zn(NO3)2 + NO + H2O
FeCl3 + H2O
CrCl3 + NaCl + CO2 + H2O
3
19.
Draw a voltaic cell using Mg in 1.0 M Mg(NO3)2 and Fe in 1.0 M
Fe(NO3)2 as the half-reactions and NaNO3(aq) as the salt bridge.
Label the cathode, anode, & salt bridge. Indicate the direction of
electron flow.
20.
Use the activity series of metals below to predict whether the
following reactions will occur spontaneously as written.
activity series of metals
a.
Fe(s) + Sn+2(aq) →
Sn(s) + Fe+2(aq)
b.
Fe+2(aq) + Cu(s) →
Fe(s) + Cu+2(aq)
c.
Zn+2(aq) + Sn(s) →
d.
2 H+(aq) + Sn(s) →
Sn+2(aq) + Zn(s)
Sn+2(aq) + H2(g)
K → K+ + e–
Ba → Ba+2 + 2e–
Ca → Ca+2 + 2e–
Na → Na+ + e–
Mg → Mg+2 + 2e–
Al → Al+3 + 3e–
Zn → Zn+2 + 2e–
Cr → Cr+3 + 3e–
Fe → Fe+2 + 2e–
Ni → Ni+2 + 2e–
Sn → Sn+2 + 2e–
Pb → Pb+2 + 2e–
H2 → 2 H+ + 2e–
Cu → Cu+2 + 2e–
As → As+3 + 3e–
Ag → Ag+ + e–
Hg → Hg+2 + 2e–
Au → Au+3 + 3e–
4
ANSWERS
1. reduced
2. oxidized
3. increase
4. decrease
5. metallic
6. electrons
7. electrolytic
8. voltage
9. spontaneous
10. non-spontaneous
13. oxidation
14. reduction
11. electron
12. Ion
Gain 5 e─
15.
5
1
H2O2 + 2
7
KMnO4 + 3
H2SO4 →
2
2
MnSO4 + 8
Lose 1 e─  2  2 e─
a.
b.
7, 2
1, 0
16.
PO3─3
H3AsO4
NaH
Ba(ClO2)2
KBrO4
C2H6
NaHCO3
3
5
1
3
7
3
4
H2O + 5
0
O2 + 1 K2SO4
5
17.
1° conductor (wire)
e─
battery
anode
cathode
M
A─
18.
2° conductor (solution)
a.
4 HCl + 2 H3MoO4 →
b.
Cl2 + 2 KBr →
c.
4 Zn + H3AsO4 + 8 HCl →
4 ZnCl2 + AsH3 + 4 H2O
d.
CoS + 8 HNO3 + 2 HCl →
CoCl2 + 8 NO2 + H2SO4 + 4 H2O
e.
3 Zn + 8 HNO3 →
f.
H2O2 + 2 FeCl2 + 2 HCl →
g.
Na2C2O2 + H2Cr2O7 + 8 HCl →
Mo2O3 + 2 Cl2 + 5 H2O
2 KCl + Br2
3 Zn(NO3)2 + 2 NO + 4 H2O
2 FeCl3 + 2 H2O
2 CrCl3 + 2 NaCl + 2 CO2 + 5 H2O
6
19.
← e─
← e─
cathode
Na
Fe
NO3─
Mg
Salt bridge
Fe+2
NO3─
20.
a.
b.
c.
d.
yes
no
no
yes
Mg+2
NO3─
anode