redox Flashcards

1
Q

what does reduction involve?

A
  • the gaining of electrons
  • decrease in oxidation state
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2
Q

oxidation involves…

A
  • the losing of electrons
  • increase in oxidation state
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3
Q

disproportionation is when…

A

the same substance undergoes both oxidation and reduction to form 2 diff products

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4
Q

when assigning oxidation no.s, the most __________ element is assigned the negative oxidation state

A

electronegative

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5
Q

what is the mnemonic for balancing equations?

use mnemonic

A

EOHC – ew our hands clashed!

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6
Q

what are the 4 steps to balancing equations for substances in acidic medium?

A

E – balance Elements that are not O or H
O – balance Oxygen by adding H2O
H – balance Hydrogen by adding H+
C – balance Charge by adding e-

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7
Q

what doe BOD stand for?

A

biochemical oxygen demand

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8
Q

what is BOD?

A

the amount of O2 used up by aerobic bacteria to decompose the organic matter in a fixed volume of water over a period of usually 5 days at 293K

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9
Q

what does standard electrode potential mean?

A

the electromotive force generated by a half cell when measured against the standard hydrogen electrode at standard conditions of 298K, 1 bar of pressure, 1 moldm-3 electrolyte

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10
Q

standard electrode potential is also… (hint: potential)

A

potential difference

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11
Q

what is a voltaic cell?

A

a system in which chemical energy is converted to electrical energy through spontaneous redox reactions

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12
Q

what are the components of a voltaic cell?

A
  • voltmeter
  • salt bridge
  • two half cells
  • connecting wires
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13
Q

what is the purpose of the salt bridge?

A
  • maintain /charge neutrality
  • completes the electrical circuit
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14
Q

in a voltaic cell, electrons flow from the

A

anode to the cathode

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15
Q

in a voltaic cell, what happens at the anode?

A

oxidation

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16
Q

in a voltaic cell at the cathode, the electrolyte undergoes…

A

reduction

17
Q

the anode in a voltaic cell is…

A

-ve

18
Q

the cathode in a voltaic cell is _____

A

+ve

19
Q

all half-cells electrode potential are measured against the ______________________

A

standard hydrogen electrode

20
Q

what are the conditions the electrode potentials are measured at?

A

gases: 100kPa
solutions: 1moldm-3
temp: 298K

21
Q

the more +ve the Eº value, the more spontaneous the _________ reaction and the __________ the oxidising agent

A

reduction, stronger

22
Q

the more -ve the Eº value, the more spontaneous the _________ reaction and the __________ the reducing agent

A

oxidation, stronger

23
Q

what is the IUPAC convention for cell notation?

A

anode|R form|O form|salt bridge|O form|R form|cathode

24
Q

what mnemonic can we use for cell notation?

A

EROSORE
Electrode: Anode
Red form
Ox form
Salt bridge
Ox form
Red form
Electrode: Cathode

25
Q

what is the eq for standard cell potentials?

A

Eºcell = Eºred - Eºox

26
Q

what is an electrolytic cell?

A

a system which converts electrical energy to chemical energy, which drives a non spontaneous reaction

27
Q

in an electrolytic cell at the anode, the electrolyte undergoes ________ while at the cathode it undergoes _________

A

oxidation, reduction

28
Q

in an electrolytic cell, the anode is ______ while the cathode is _______

A

+ve, -ve

29
Q

in a voltaic cell, the anode is _____ while the cathode is ________

A

-ve, +ve

30
Q

the reaction that occurs in an electrolytic cell at both the cathode and anode has a more _______ Eº value

A

magnitude

31
Q

what does Eº measure?

A

tendency of the forward rxn

32
Q

what happens to Eº when the conc of an electrolyte (e.g. aq NaCl) is incr in an electrolytic cell?

A
  • high [Cl-] shifts POE to the right
    • fwd rxn is favoured
    • causes Eº to become more (+)ve (Eº measures tendency of forward rxn)
  • high [Na+] shifts POE to the right
    • fwd rxn is favoured
    • Eº becomes more (-)ve however it is still less than water
33
Q

when Eºox becomes more (+)ve, how does this change the value of Eºcell?

A

causes Eºcell to increase in magnitude

34
Q

what is the eqn for current, electricity and time

A

Q = I x t

Q= amt of electricity/C
I= strength of current/A
t= time/s

35
Q

what is the eqn to find the amount of product formed in the electrolytic process?

A

Q = ne x F

Q= amt of current/C
ne= no. moles of e- transferred
F= Faraday’s constant

36
Q

in electroplating, the object being electroplated is placed at the…

A

cathode

37
Q

does SO4^2- get reduced or oxidised?

A

it does not get oxidised or reduced

38
Q

___ always gets reduced and ____ always gets oxidised

A

Cu, Br