Download Answers for Review Questions Exam 3

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Transcript
Answers for Review Questions Exam 3
1. A
2. C
3. D
4. C or D
5. B
6. A
7. A
8. Primary Battery – Uses a redox reaction that cannot be reversed easily, so when the
cell reaction reaches equilibrium, the battery is dead. Ex. Dry cell
battery, Mercury, Lithium batteries, Alkaline Batteries. Problems:
Can’t be reused, Dry battery- produces gaseous products, poor shelf
life. Mercury Battery – poisonous.
Secondary Battery – Uses a redox reaction, which is recharged by applying an external
current. Ex. Lead storage battery. Ni-cad batteries, Problems:
Lead Storage – High mass to power ratio, high mass but little
power.
9. Electrolysis is the use of an electric current to bring about a chemical change.
Reduction and oxidation both occur at the same place as in a galvanic cell, but they
have different polarities, - and + respectively. It differs from a galvanic cell in that it
is in the opposite direction of a galvanic cell and the polarities in a galvanic cell are
the opposite of those in electrolysis.
10. Electrolysis is used as a source of elements from their ions. Ex. Na from Molten
NaCl, Cl2 from a NaCl solution.
11. 0.1663 A current is needed.
12. First 2.47 Volts should be 2.47 Amperes. That gives 4.100g of Fe deposited.
13. Corrosion is the loss of metals to a solution of some form. The process that occurs is
the oxidation of the metal and the reduction of water, followed by the formation of a
metal hydroxide.
14. Because not all metals are easily oxidized by water. H2O and O2 are the two main
substances. Keep the reactants apart: form a protective layer (ex. Oxide or Paint).
Force the anode to act as a cathode: Use a zinc covering as a sacrificial anode.
15. Use a voltage of 4.6 V. This give you 1.0287 x 1025 electrons passed through the
solution.
16. Metallic Character, Ionic Radii, Atomic Radii, Electronegativety, Electron Affinity,
Ionization Energy. Refer to notes on exact directions of trends.
17. a. KCN
b. NiS c. Ca3(PO4)2 d. Na2SO3
e. Al(NO2)3
18. a. +1, +1
b. +2, +8
19. a. 2Ca + O2
c. +2,+2
2CaO
Basic
b. C + O2
CO2
Acidic
c. Ge + O2
GeO2
Basic
d. Se + O2
SeO3
Acidic
e. Sn + O2
SnO2
Basic
f. Ga + O2
GaO3
Basic
g. 4Rb + O2
Rb2O
Basic
h. Al + O2
Al2O3
Basic
i. Cr + O2
CrO3
Basic
j. N2 + O2
NO3-
Acidic
d. +1,+1
e. +3,+3
20. Some methods are the reaction of methane with steam, electrolysis of water, reaction
of a metal and an acid, water or a base, and finally a metal hydride with water. In the
past it was used as a heating fuel. It is also used to form ammonia and primarily as a
reactant for many reactions.
21. a.+1
b.+1
c.+1d.+1
e.–1
f.–1
g.–1
h.–1
i.+1
j.–1
k.+1
l.+1
22. a.
23. d.
24. Lanthanide Contraction is where the second third row of transition metals are shown
to have approximately the same atomic radii. This is caused by the increase of
protons as the f- block metals are added. This results in a higher effective nuclear
charge which in turn “pulls” the electrons in more than what is thought from the
trend.
25. Magnetism is a result of unpaired electrons in the outer electron shell. There are
several forms of magnetism. The first is diamagnetism, of which species have paired
electrons, where there is a strong repulsion of a magnetic force. Then comes
paramagnetism where electrons are not paired and are strongly attracted to a
magnetic field. Last is ferromagnetism is where there are unpaired electrons, which
line up in together and are strongly magnetic that their effect is recognizable.