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CHEM352 > second half of electrochem > Flashcards

second half of electrochem Flashcards

1
Q

describe lead-acid battery

A

low energy density, high power density

all in the solid state,

Ecell = 2.04V

a polyethylene membrane acts as a separator and prevents short circuiting of the battery during charging

water hydrolysed during charging so has to be topped up

90% efficiency for discharge

heavy so low specific energy and reduced cyclability

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2
Q

describe nickel metal hydride cells

A

good specific energy and power

rechargeable

safe, low maintenance

expensive, hard to recycle, high self-discharge rate

KOH as the electrolyte

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3
Q

what is the cathode and its cell potential for nickel metal hydride cells

A

Ni(OH)2 + OH- -> NiOOH + H2O + e-

cell potential std = 0.25 V

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4
Q

what is the anode and its cell potential for nickel metal hydride cells

A

H2O + M + e- -> MH + OH-

cell potential = -1.1V

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5
Q

what is the cathode for alkaline cells

A

MnO2 + H2O + 2e- -> Mn2O3 + 2OH-

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6
Q

what is the anode and its cell potential for alkaline cells

A

Zn + 2OH- -> ZnO + H2O + 2e-

EAN = -1.28V

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7
Q

what is the cell potential for alkaline cells

A

1.43V

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8
Q

describe alkaline cells

A

non-rechargeable

leak KOH

easy to recycle & recover the SM

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9
Q

Describe lithium batteries

A

high cell potential

high specific energy and power
rechargeable for more cycles than nickel metal hydride cells
very low self-discharge rate
hazardous (explosive H2 gas & Li is very reactive w/ water)

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10
Q

what are the three methods of Li transport in batteries?

A

1D channels (olivine) , 2D layered, 3D framework (spinel)

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11
Q

for lithium and graphite cell what is the cathode?

A

CoO2 + Li+ + e- -> LiCoO2

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12
Q

for lithium and graphite cell what is the anode?

A

LiC6 -> C6 + Li+ + e-

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13
Q

How does the lithium and graphite cell overdischarge?

A

irreversible formation of Li2O

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14
Q

How does the lithium and graphite cell overcharge?

A

collapse of the layered structure and irreversible formation of amorphous Co(IV) oxide

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15
Q

What are the electrolytes in Li batteries?

A

NOT AQ - generally carbonates or ethers to prevent reaction w/ Li

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16
Q

How is LiBF2(C2O4) used in lithium batteries?

A

to increase cyclability and side reactions - forms a protecting layer on the electrodes to increase stability

17
Q

what is the point of solid electrolytes? egs?

A

no leakage, no fire hazard

polymer-based

ceramic - has Li transport channels

18
Q

what is m in faraday’s law

A

the no. of moles of reactant or product consumed/formed

19
Q

what are the products of the chloroalkali process and their uses?

A

Cl2 - to make plastics and water & silicon purification

NaOH

H2 - energy in fuel cells

20
Q

positive electrode eqs in the chloroalkali process

A

2Cl- -> Cl2 + 2e- = 1.36V

2H2O -> 4H+ + O2 + 4e- = 1.23V

21
Q

why is Cl2 released and not O2 in chloroalkali positive electrode

A

strong kinetic barrier of overpotential on the Pt electrodes

22
Q

negative electrode eqs in the chloroalkali process and their potentials

A

2H2O + 2e- -> H2 + 2OH- = -0.83 V

Na+ + e- -> Na(s) = -2.71V

23
Q

why is H2 released and not Na reduction in chloroalkali negative electrode

A

H2 evolution is at less negative potential = favoured, smaller kinetic barrier

24
Q

angle for philicity

A

contact angle CA <90

25
Q

angle for phobicity

A

CA >90

26
Q

what does Jurin’s law show?

A

the capillary action is inversely proportional to the radius of the capillary

27
Q

which end of surfactants are hydrophobic and hydrophillic

A

polar = hydrophillic
hydrocarbon chain = hydrophobic

28
Q

how do micelles form?

A

polar ends interact with the aqueous environment and the hydrocarbon chains pointing inwards

29
Q

what direction does the YSG face?

A

away from the edge of the droplet (from the surface to the gas)

30
Q

what direction does the YSL face?

A

into the edge of the droplet (from the surface to the liquid)

31
Q

what direction does the YLG face?

A

up inbetween the SG and SL

32
Q

where is theta for the YSG/YLG/YSL

A

inbetween the YLG and the YSL

33
Q

what is a in the film pressure eq

A

surface area per mole

34
Q

what is a colloid?

A

a homogenous non-crystalline substance consisting or large molecules or microscopic particles dispersed through a second substance

CHEM352 (4 decks)

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