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MCAT chem > redox and electrochemistry > Flashcards

redox and electrochemistry Flashcards

1
Q

oxidation

A

lose e-

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2
Q

reduction

A

gain e-

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3
Q

redox reactions

A

e- are transfrered and one molecule gains e- while one loses e-
- oxidation state of compounds changes

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4
Q

oxidation state

A

measured using oxidation numbers
- keep track of how e- are shared in a molecule
- model of electron distribution where e- is given to most eneg atom

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5
Q

oxidation state rule for pure atoms

A

pure elements in natural form like diatomics have an oxidation state of 0
ex: o2

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6
Q

what is oxidation state of monoatomic ion

A

its charge
ex: mg is 2+

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7
Q

what is true about the sum of oxidation states among atoms in a molecule

A

they add up to the overall charge of the molecule

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8
Q

oxidation state of F

A

-1, oxidizing agent

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9
Q

oxidation state of most halonges

A

-1

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10
Q

what is oxidation state of cholrine in HClO4

A

+7

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11
Q

oxidation state of hydrogen

A

usualyl 1+ unless bonded to a more electropositive atom like NAH and LIAlH

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12
Q

oxidation state of oxygen

A

usually -2 unless peroxide, then its -1

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13
Q

oxidation state of alkali metals

A

1+

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14
Q

oxidation state of alkali earth metals

A

2+

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15
Q

nonredox reactions

A

overall, the distribution of e- does not change
acid base, subsitution reactions, precipitation reactions , double displacement reactions

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15
Q

nonredox reactions

A

overall, the distribution of e- does not change
acid base, subsitution reactions, precipitation reactions , double displacement reactions

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15
Q

nonredox reactions

A

overall, the distribution of e- does not change
acid base, subsitution reactions, precipitation reactions , double displacement reactions

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15
Q

nonredox reactions

A

overall, the distribution of e- does not change
acid base, subsitution reactions, precipitation reactions , double displacement reactions

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16
Q

classic redox

A

single displacement

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17
Q

is combustion a type of redox

A

yes
something + 02 –> co2 + h2o

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18
Q

are combination reactions redox

A

yes
free elements –> compound

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19
Q

how to balance redox reactions

A
  1. split into half reactions
  2. balence non O and non H atoms
  3. balence ox
  4. balence H
  5. balence e-
  6. multiply so both half rxn has same amount of e-
  7. add/ cancel like terms
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19
Q

how to balance redox reactions

A
  1. split into half reactions
  2. balence non O and non H atoms
  3. balence ox
  4. balence H
  5. balence e-
  6. multiply so both half rxn has same amount of e-
  7. add/ cancel like terms
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20
Q

how to balance redox reactions

A
  1. split into half reactions
  2. balence non O and non H atoms
  3. balence ox
  4. balence H
  5. balence e-
  6. multiply so both half rxn has same amount of e-
  7. add/ cancel like terms
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21
Q

oxidation agent

A

is reduced and promotes oxidation of other reagnet
typically contain oxygen or other electronegative atoms

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22
Q

reducing agent

A

is oxidized and promotes reduction of other reagent
tend to have hydrogen

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23
Q

PCC

A

common oxidizing agent (weak)

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24
Q

NaBH4

A

common reducing agent

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25
Q

LiAlH4

A

common reducing agent

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26
Q

reduction potential

A

how likely something is to be reduced, higher value = more likely to be reduced

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27
Q

oxidation potential

A

reduction potential = - oxidation potential

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28
Q

standard potential of a cell

A

measured as reduction potential

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29
Q

what do all electrochemical cells have

A

a cathode and an anode

30
Q

anode

A

electrode where oxidation happens
-surplus of e- generated that travel to the cathode

31
Q

cathode

A

Electrode where reduction happens

32
Q

galvanic cell

A

spontaneous redox reaction that generates a positive V difference

33
Q

cell potential eqn

A

E cell = Ecathode - E anode

34
Q

which electrode possesses the reduction potential in a galvanic cell

A

cathode (spontaneous rxn )

35
Q

cell potential eqn for a galvanic cell

A

E cell = E cathode - E anode

36
Q

another way of establishing the cell potential formula

A

E cell = reduction potential of cathode + oxidation potential of anode

37
Q

Nerst Eqn

A

how electrical potential of a cell is effected by temperature and concentration of reactants
E’cell = E cell - RT/zf * lnQ

38
Q

E’ cell

A

actual electrical potential of cell under given conditions

39
Q

z in nertz eqn

A

moles of e- transfered

40
Q

F in nertz eqn

A

faraday constant

41
Q

q

A

reaction quotient
[products]/[reactants]

42
Q

physiology nertz eqn

A

E’cell = standard potential - .05916/ z(logq)

43
Q

Daniell cell

A

typical set up of a galvanic cell
- half reactions are carried out in two separated half cells
- electrodes are connected by a wire and a salt bridge (does not interfere with redox rxns
-

43
Q

purpose of salt bridge

A

to prevent strong charge gradient buildup and hindering progress of rxn

44
Q

Daniell cell

A

typical set up of a galvanic cell
- half reactions are carried out in two separated half cells
- electrodes are connected by a wire and a salt bridge (does not interfere with redox rxns
-

45
Q

what happens to the zinc electrode (anode)

A

it becomes smaller as oxidation continues and e- are being stripped

46
Q

what happens to the sulfur electrode (cathode)

A

will grow because of increased e-

47
Q

galvanic cell notation

A

anode is on right || cathode is on left

48
Q

charge of galvanic anode

A
  • because it is the source of electrons
49
Q

charge of galvanic cathode

A

positive because it has greater potential to be reduced

50
Q

concentration cells

A

galvanice cells where the two half reations occur in the same cell
1. electrodes must be made out of same material
2. must be a concentration difference between the two regions of the cell

51
Q

biological example of concentration cells

A

cell membrane with concentration difference between inside and outside of cell

52
Q

electrolytic cells

A

apply energy to system and produce reaction in nonspontaneous direction
break down into components

53
Q

which electrode is location of reduction in electrolytic cells

A

cathode, marked with a negative charge

54
Q

anode of electrolytic cell

A

positive and where oxidation takes palce

55
Q

portion of battery that provides charge

A

galvanic

56
Q

portion of battery that allows for recharge

A

electrolytic

57
Q

benedicts reagent

A

reduce cu2+ to cu , dark blue color change

58
Q

connection between standard gibbs free energy and electric potential

A

ΔG= -nFEcell
n = moles of electrons moved
f is faradays constant

59
Q

how does standard potential relate to Keq

A

nFEcell = RTlnkeq

60
Q

if the standard redox potential of a cell is positive what happens to gibbes free enrgy

A

negative so spontaneous

61
Q

trade off in galvanic cell

A

using spontaneous chemical reaction to provide electrical energy

62
Q

half reactions of galvanic cell

A

zinc and copper
Zu –> Z 2+ + 2 e-
Cu 2+ + 2e- –> cu

63
Q

half cell

A

seperated containers with metal electrodes
either cathode or anode

64
Q

electrode on left of galvanic cell

A

zn

65
Q

electrode on right of galvanic cell

A

cu

66
Q

what allows e- to flow from zinc to copper in galvanic cell

A

the current carrying wire

67
Q

zn electrode in galvanic cell

A

anode
negative
oxidation

68
Q

cu electrode in galvanic cell

A

cathode
positive (e- move toward positive)
reduction

69
Q

galvanic electrodes mnuemonic

A

An Ox and Red Cat
- anode, oxidation
- cathode, reduciton

70
Q

electrolysis

A

uses external energy to power nonspontaneous (electrolytic ) reaction
- often used to split molecules –> make pure metals
requires voltage source

71
Q

half reactions of electrolytic cells

A

2 na+ + 2 e- –> 2 Na (s) red
2 cl- –> cl2 + 2 e- (g) ox

72
Q

does electrolytic reaction happen in 2 containers (like galvanic) or one?

A

only one, and there is no aqueous solution. only the ions na + and Cl-

73
Q

anode of electrolytic cell

A

on left
is positive
still oxidation
2 cl - –> cl2 + 2 e-
ELECTRONS FLOW FROM ANODE TO BATTERY

74
Q

cathode of electrolytic cell

A

Na+ +2 e- –> na
is negative
reduction
ELECTRONS ARE FLOWING FROM BATTERY TO CATHODE

75
Q

what side of the battery is the electrolytic cathode attatched to

A

negative

MCAT chem (11 decks)

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