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Homework 4-solutions-1

Homework 4-solutions-1 - jaw2435 Homework 4 Walker(53985...

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jaw2435 – Homework 4 – Walker – (53985) 1 This print-out should have 24 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 1.0 points Silicon has four valence electrons. The dopant used in an n-type silicon semiconduc- tor should have 1. three valence electrons. 2. five valence electrons. correct 3. four valence electrons. 4. two valence electrons. Explanation: 002 1.0 points The removal of silver tarnish from silverware using aluminum foil and a solution of elec- trolyte is an example of 1. oxidation of aluminum metal. 2. reduction of silver ions. 3. an example of an electrochemical cell. 4. All of these correct Explanation: 003 1.0 points When a ring is gold plated by the electochem- ical process Au 3+ + 3 e - Au, the ring should be made the ? of an elec- trolytic cell. 1. dopant 2. battery 3. cathode correct 4. anode Explanation: The gold ions need to be reduced to be plated. Reduction occurs at the cathode, so the ring should be made the cathode. 004 1.0 points A battery is a device that converts chemical energy into 1. chemical energy. 2. light energy. 3. nuclear energy. 4. electrical energy. correct Explanation: 005 1.0 points For a 12 volt car battery to deliver lots of cur- rent, which of the following is most critical? 1. keeping the solution in the battery cool 2. keeping the sulfuric acid concentration very low 3. having electrodes with lots of surface area correct 4. guaranteeing reversibility of the half-cell reactions 5. keeping the electrodes as reduced as pos- sible Explanation: 006 1.0 points The acid in automobile batteries is 1. nitric acid. 2. sulfuric acid. correct 3. phosphoric acid. 4. hydrochloric acid. Explanation: 007 1.0 points
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jaw2435 – Homework 4 – Walker – (53985) 2 A fuel cell is an electrochemical device that 1. burns gasoline to produce heat. 2. converts coal to a gas. 3. produces fuels from water. 4. converts chemical energy directly to elec- trical energy. correct Explanation: 008 1.0 points What is the principal element used in a photo voltaic cell? 1. boron 2. arsenic 3. germanium 4. silicon correct 5. phosporus Explanation: Silicon is used in both p -type and n -type photovoltaic cells. 009 1.0 points One of the advantages of hydrogen fuel cells as an energy source for space travel is 1. the water produced by the cell can be used for other purposes. correct 2. fuel cells produce more energy in the vac- uum of space.
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Homework 4-solutions-1 - jaw2435 Homework 4 Walker(53985...

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