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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.