Chapter 20: Electrochemistry

Question 1

What is an oxidant? (oxidizing agent)

Answer 1

gets reduced so it could oxidize something

Question 2

Do oxidants gain or lose electrons?

Answer 2

gain

Question 3

What is a reductant? (reducing agent)

Answer 3

gets oxidized so it could reduce something

Question 4

Do reductants gain or lose electrons?

Answer 4

lose

Question 5

What are voltaic cells?

Answer 5

device in which the transfer of electrons between two reactants take place

Question 6

How do voltaic cells work?

Answer 6

2 reactants not in direct contact (2 separate cells) | redox rxn occurs via flow of e- through electrodes and wires

Question 7

What is an electrical current?

Answer 7

consists of flowing electrons 9can do electrical work) through a wire and ions moving in solution

Question 8

What occurs at an anode?

Answer 8

oxidation

Question 9

What occurs at a cathode?

Answer 9

reduction

Question 10

What ions in solution migrate toward the anode in a voltaic cell?

Answer 10

anions

Question 11

What ions in solution migrate toward the cathode in a voltaic cell?

Answer 11

cations

Question 12

What is potential difference?

Answer 12

difference in potential energy per electrical charge

Question 13

What is 1 volt equivalent to?

Answer 13

1 Joule/Coulomb

Question 14

What is cell potential (Ecell)?

Answer 14

potential difference between two electrodes

Question 15

What is electromotive force (emf)?

Answer 15

its a potential difference that causes the driving force that pushes the electrons through the wire

Question 16

What is “emf” also called?

Answer 16

the voltage of a cell

Question 17

What sign must Ecell of a voltaic cell system must have?

Answer 17

(+)

Question 18

What are standard conditions?

Answer 18

1M, 25ºC, and 1 atm

Question 19

What 3 things does the magnitude of Ecell depend on?

Answer 19

reactions occuring at cathode and anode | concentrations of the reactions and products | temperature

Question 20

What is Eºcell?

Answer 20

Ecell under standard conditions

Question 21

What is the reference half-reaction?

Answer 21

the Eºreduction of 1 atm hydrogen gas

Question 22

What does SHE stand for?

Answer 22

standard hydrogen electrode

Question 23

What is standard hydrogen electrode?

Answer 23

the electrode that produces the hydrogen gas reference half reaction | platinum wire

Question 24

When looking at Eºreduction standard cell potentials, how do you determine which occurs at the cathode or anode?

Answer 24

the more negative the value = more it will be oxidized | the more positive the value = more it will be reduced

Question 25

What kind of process (spontaneous or not) is a (-)E?

Answer 25

nonspontaneous

Question 26

What kind of process (spontaneous or not) is a (+)E?

Answer 26

spontaneous

Question 27

What is the value for Faraday’s constant?

Answer 27

96485 C/mol or J/V•mol

Question 28

When is the Nernst equation used?

Answer 28

nonstandard conditions (varying concentrations)

Question 29

What is a concentration cell?

Answer 29

a cell based solely on the emf made from difference in concentration

Question 30

What is a battery?

Answer 30

portable, self-contained electrochemical power source that consists of one or more voltaic cells

Question 31

What are primary batteries?

Answer 31

cannot be recharged | throw away when voltage drops to 0

Question 32

What are secondary batteries?

Answer 32

rechargeable from an external power source when voltage drops

Question 33

What are the 3 types of SECONDARY batteries?

Answer 33

lead-acid (car) batteries | Nickle-Cadmium/metal hydride batteries | lithium-ion batteries

Question 34

What is a non-rechargeable battery?

Answer 34

alkaline batteries

Question 35

What are fuel cells?

Answer 35

voltaic cells that convert chemical energy into electrical energy via conventional fuels (ie: CH4)

Question 36

What are the 2 reasons as to why fuel cells are not batteries?

Answer 36

not self-contained | fuel must be continually supplied to produce electricity

Question 37

What is corrosion?

Answer 37

spontaneous redox reactions | metal is attacked by some substance from surroundings = converted into an unwanted compound (ie: rust = iron oxide)

Question 38

How can you prevent corrosion of iron?

Answer 38

paint over it or cover it with another metal = which will act as a protective layer

Question 39

What is galvanized iron?

Answer 39

iron covered in zinc = zinc acts as the anode and gets oxidized

Question 40

What is cathodic protection?

Answer 40

process of preventing corrosion by making the metal into the cathode (as anode gets oxidized = corrosion)

Question 41

What is a sacrificial anode?

Answer 41

metal oxidized while protecting the cathodic metal

Question 42

How can nonspontaneous (-)Ecell reactions happen?

Answer 42

only when the driving force is electrical energy (ie battery not flow of electrons

Question 43

What are electrolysis reactions?

Answer 43

redox rxns driven by an outside source of electrical energy

Question 44

Where do electrolysis reactions occur?

Answer 44

electrolytic cells

Question 45

What is an electrolytic cell?

Answer 45

one whole cell (not separate) with 2 electrodes

Question 46

What is an electron pump?

Answer 46

the voltage source forcing the electrons one specific way

Question 47

What is the orientation (+)/(-) at the cathode and anode in electrolytic cells?

Answer 47

anode = (+) | cathode = (-) || anode still oxidizes | cathode still reduces

Question 48

What is the flow of electrons in an electrolytic cell?

Answer 48

anode —-> cathode