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Chemistry 1100 > Exam #4 Prep > Flashcards

Exam #4 Prep Flashcards

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1
Q

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

A

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

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2
Q

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

A

the nature of the materials in the reaction

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3
Q

What is the oxidation half-reaction?

A

Zn –> Zn^(2+) + 2e-

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4
Q

What is the oxidation half-reaction?

A

Zn –> Zn^(2+) + 2e-

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5
Q

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

A

be able to generate electricity where we cannot do so now

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6
Q

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

A

liquify under pressure

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7
Q

What is the max efficiency of a solar cell?

A

40%

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8
Q

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

A

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

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9
Q

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

A

nickel metal hydride

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10
Q

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

A

arsenic

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11
Q

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

A

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

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12
Q

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

A

batteries must store/supply energy when there is no sun

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13
Q

Whenever a substance is oxidized…

A

another substance must be reduced

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14
Q

Whenever a substance is oxidized…

A

another substance must be reduced

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15
Q

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

A

boiling water breaks intermolecular attractions, electrolysis breaks covalent bonds

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16
Q

What is the whole chemical reaction of a galvanic cell?

A

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

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17
Q

PEM fuel cells….

A
  • are cleaner than gasoline powered vehicles
  • are safe/efficient fuel storage
  • have a limited driving range
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18
Q

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

A

galvanic cell

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19
Q

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

A

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

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20
Q

A major advantage of fuel cells over batteries is…

A

as long as O2 and fuel are supplied, the fuel cell won’t “run down”

21
Q

Where does reduction take place in a fuel cell?

A

at the cathode

22
Q

Where does reduction take place in a fuel cell?

A

at the cathode

23
Q

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

A

rate of electron flow through that wire

24
Q

How is wind energy related to the sun?

A

heat of sun drives large scale movements of air

25
Q

Difficult to develop an economy based on H2 because…

A

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

26
Q

What increases the efficiency of a photovoltaic/solar cell?

A
  • 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
Q

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

A

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

28
Q

In an electrochemical cell, the anode is…

A

the electrode where oxidation occurs

29
Q

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

A

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

30
Q

Which has a lower melting point, HDPE or LDPE?

A

LDPE

31
Q

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

A

crystalline region

32
Q

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

A

functional groups

33
Q

What does a peptide bond look like?

A

N=C

34
Q

What do the “Big Six” polymers have in common?

A

they are thermoplastics

35
Q

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

A

plasticizers

36
Q

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

A

plasticizers

37
Q

PET contains what sort of linage between monomer units?

A

ester

38
Q

Which raw material serves as source for most polymers?

A

crude oil

39
Q

What is an amine group?

A

NH2

40
Q

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

A

PS

41
Q

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

A

PS

42
Q

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

A

polyamides

43
Q

What is electrolysis?

A

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

44
Q

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

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

45
Q

Cellulose is classified as a…

A

condensation homopolymer

46
Q

Sunlight may be turned directly into electricity using _____

A

photovoltaic cells

47
Q

What is the oxidation half-reaction?

A

Zn –> Zn^(2+) + 2e-

48
Q

Whenever a substance is oxidized…

A

another substance must be reduced

49
Q

Where does reduction take place in a fuel cell?

A

at the cathode

Chemistry 1100 (11 decks)

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