Exam #4 Prep Flashcards Preview

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Flashcards in Exam #4 Prep Deck (49):
1

Why does a fuel cell not "run down" like a standard battery?

the reactants in a battery must be stored inside the battery whereas the reactants for a fuel cell flow as needed

2

What is the primary determinant of the voltage developed by a battery?

the nature of the materials in the reaction

3

What is the oxidation half-reaction?

Zn --> Zn^(2+) + 2e-

4

What is the oxidation half-reaction?

Zn --> Zn^(2+) + 2e-

5

As fuel wells become more widely accepted and are used more, we will...

be able to generate electricity where we cannot do so now

6

Which has NOT been suggested as a reasonably practical way to store large amounts of H2 in small spaces?

liquify under pressure

7

What is the max efficiency of a solar cell?

40%

8

Why can the lead-acid batteries in cars generate electricity for several years before running down?

the mechanical motion of the engine drives an alternator that generates electricity to recharge the battery

9

What battery shouldn't have to be replaced in a hybrid car?

nickel metal hydride

10

What metal is used to "dope" a n-type semiconductor?

arsenic

11

What are necessary considerations for a battery designed to run a cell phone?

must develop a useful level of electrochemical potential, must "run" for a reasonable amount of time, must be lightweight

12

Batteries must be used in addition to solar cells when generating household electricity because....

batteries must store/supply energy when there is no sun

13

Whenever a substance is oxidized...

another substance must be reduced

14

Whenever a substance is oxidized...

another substance must be reduced

15

How do interactions that are broken in water when it is boiled compare to those when it is electrolyzed?

boiling water breaks intermolecular attractions, electrolysis breaks covalent bonds

16

What is the whole chemical reaction of a galvanic cell?

Cd(s) + 2NiO(OH)(s) + 2H2O)l) --> 2Ni(OH)2(s) + Cd(OH)2(s)

17

PEM fuel cells....

-are cleaner than gasoline powered vehicles
-are safe/efficient fuel storage
-have a limited driving range

18

Chemical energy is converted directly into electrical energy in a ....

galvanic cell

19

How do you generate electricity in a solar cell when p-type and n-type semiconductors are placed in contact by a wire?

light shining on system must have enough energy to set electrons in motion from n-type to p-type

20

A major advantage of fuel cells over batteries is...

as long as O2 and fuel are supplied, the fuel cell won't "run down"

21

Where does reduction take place in a fuel cell?

at the cathode

22

Where does reduction take place in a fuel cell?

at the cathode

23

The current through a wire is most closely related to the...

rate of electron flow through that wire

24

How is wind energy related to the sun?

heat of sun drives large scale movements of air

25

Difficult to develop an economy based on H2 because...

hydrogen is abundant, but pure H2 isn't natural on earth --> difficult and costly to isolate and collect

26

What increases the efficiency of a photovoltaic/solar cell?

-replacing crystalline with non-crystalline silicon
-increasing the number of alternating p and n-type layers of semiconductors
-decreasing the thickness of each alternating p and n type layers of semiconductors

27

Why doesn't water naturally split into H2 and O when in light?

water doesn't absorb the proper wavelength of light to split

28

In an electrochemical cell, the anode is...

the electrode where oxidation occurs

29

Semiconductors are more effective converters of solar radiation than metals because...

energy is sunlight gives valence electron in the semiconductor extra energy they need to "flow" through the solid

30

Which has a lower melting point, HDPE or LDPE?

LDPE

31

The regions of a polymer where the long polymer molecules are arranged neatly/tightly in a regular patter is called the _______

crystalline region

32

The distinctive arrangements of atoms that impart characteristic chemical properties to the molecules that contain them are called _______

functional groups

33

What does a peptide bond look like?

N=C

34

What do the "Big Six" polymers have in common?

they are thermoplastics

35

What are the molecules added to polymers to make them softer/more pliable?

plasticizers

36

What are the molecules added to polymers to make them softer/more pliable?

plasticizers

37

PET contains what sort of linage between monomer units?

ester

38

Which raw material serves as source for most polymers?

crude oil

39

What is an amine group?

NH2

40

Which synthetic polymer has two forms (crystal and expandable)?

PS

41

Which synthetic polymer has two forms (crystal and expandable)?

PS

42

Skin, hair, muscle, and enzymes are all made of protein which is a natural polymer. What polymer?

polyamides

43

What is electrolysis?

a process that requires an electrical current to break water into hydrogen gas and oxygen gas

44

How does using hydrogen as the fuel to boil water in an electric power plant compare with using hydrogen as the fuel in a fuel cell?

a fuel cell using hydrogen operates at a higher overall efficiency than would a power plant burning hydrogen as fuel

45

Cellulose is classified as a...

condensation homopolymer

46

Sunlight may be turned directly into electricity using _____

photovoltaic cells

47

What is the oxidation half-reaction?

Zn --> Zn^(2+) + 2e-

48

Whenever a substance is oxidized...

another substance must be reduced

49

Where does reduction take place in a fuel cell?

at the cathode