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Chemistry: Electrode Potentials Part 4

Chemistry30 CardsCreated 2 months ago

This deck covers key concepts related to non-rechargeable and rechargeable cells, lithium-ion cells, the effect of concentration on cell emf, and commercial applications of electrochemical cells.

Non rechargeable cells: function of carbon rod

Allows electrons to flow
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Key Terms

Term
Definition
Non rechargeable cells: function of carbon rod
Allows electrons to flow
Non rechargeable cells: why cell often leaks after being used for a long time
Zn used up as reaction proceeds
Rechargeable cells: why can they be recharged
Reaction occurring in cell can be reversed and chemicals in cell regenerated

Rechargeable cells: examples

  • lead/acid- cars

  • Ni/Cd- torches/radios

  • lithium/ion-phones, tablets, cameras etc

Lithium ion cells: why are they light
Lithium is the least dense mental
Lithium ion cells: reaction occurring at positive electrode
Co(IV) reduced to Co(III)

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TermDefinition
Non rechargeable cells: function of carbon rod
Allows electrons to flow
Non rechargeable cells: why cell often leaks after being used for a long time
Zn used up as reaction proceeds
Rechargeable cells: why can they be recharged
Reaction occurring in cell can be reversed and chemicals in cell regenerated

Rechargeable cells: examples

  • lead/acid- cars

  • Ni/Cd- torches/radios

  • lithium/ion-phones, tablets, cameras etc

Lithium ion cells: why are they light
Lithium is the least dense mental
Lithium ion cells: reaction occurring at positive electrode
Co(IV) reduced to Co(III)
Lithium ion cells: reaction occurring at negative electrode
Li(0) oxidised to Li(+1)
Lithium ion cells: equation for discharge of cell
CoO2 + Li > Li+[CoO2]-

Lithium ion cells: equation for recharging cell

Discharge reaction reversed

| Li+[CoO2]- > CoO2 + Li

The effect of concentration on the emf of a cell (eg Zn|Zn2+||Cu2+|Cu): what will happen if [Cu2+]<1moldm-3

  • equilibrium shift LHS

  • ECu less positive

  • Cu2+ will gain feevwr electrons

  • Ecell will decrease- cell has smaller difference in E

The effect of concentration on the emf of a cell (eg Zn|Zn2+||Cu2+|Cu): what will happen if [Zn2+]>1mol dm-3

  • equilibrium will shift RHS

  • EZn less negative

  • Zn will release fewer electrons

  • Ecell will decrease as cell has smaller difference in E

The effect of concentration on the emf of a cell (eg Zn|Zn2+||Cu2+|Cu): what will happen if [Zn2+] < 1moldm-3

  • equilibrium shift LHS

  • EZn become more negative

  • Zn will release more electrons

  • Ecell will increase as cell has a bigger difference in E

if conditions are no longer standard what is cell potential written as as opposed to E0Cell
ECell
Limitations of using electrode potentials to predict redox reactions
predictions using electrode potentials tell us about equilibrium but not RoR many reactions in laboratory not done under standard conditions- will affect electrode potential vales

Commercial applications of electrochemical cells: what 3 main types can cells be divided into

  • non- rechargeable cells

  • rechargeable cells

  • fuel cells

Non rechargeable cells: how are they designed to be used only once
Reactions occurring in cells cannot be reversed
Non rechargeable cells: what will happen when the chemicals are used up
The battery will go flat and the emf will fall to 0.00V
Non rechargeable cells: used in
Smoke detectors and clocks
Non rechargeable cells: overall equation of zinc and manganese dioxide cell when it discharged
2MnO2 + 2H2O + Zn > 2MnO(OH) + 2OH- + Zn2+
Non rechargeable cells: function of porous separator
Allows ions to flow
Non rechargeable cells: function of carbon rod
Allows electrons to flow
Non rechargeable cells: why cell often leaks after being used for a long time
Zn used up as reaction proceeds
Rechargeable cells: why can they be recharged
Reaction occurring in cell can be reversed and chemicals in cell regenerated

Rechargeable cells: examples

  • lead/acid- cars

  • Ni/Cd- torches/radios

  • lithium/ion-phones, tablets, cameras etc

Lithium ion cells: why are they light
Lithium is the least dense mental
Lithium ion cells: reaction occurring at positive electrode
Co(IV) reduced to Co(III)
Lithium ion cells: reaction occurring at negative electrode
Li(0) oxidised to Li(+1)
Lithium ion cells: equation for discharge of cell
CoO2 + Li > Li+[CoO2]-

Lithium ion cells: equation for recharging cell

Discharge reaction reversed

| Li+[CoO2]- > CoO2 + Li

Fuel cells: what does it use to create a voltage
Energy from the reaction of a fuel with oxygen