Электр энергияның химиялық көздері. Автокөліктің аккумуляторы. Сутекті-оттекті отын элементі. Химия, 10 сынып, презентация.

ELECTROCHEMISTRY

© www.chemsheets.co.uk A2 1077 2-July-2016

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Objectives

- understand electrochemical cells as a source of energy, including the constituents of commercial cells

- understand the processes of charging and discharging cells

- understand the construction and operation of a hydrogen-oxygen fuel cell

- understand the benefits and potential risks of fuel cells

Electrochemical cells

i appreciate that electrochemical cells can be used as a commercial source of electrical energy

j appreciate that cells can be non-rechargeable (irreversible), rechargeable and fuel cells

k be able to use given electrode data to deduce the reactions occurring in non-rechargeable and rechargeable cells and to deduce the e.m.f. of a cell

l understand the electrode reactions of a hydrogen-oxygen fuel cell and appreciate that a fuel cell does not need to be electrically recharged

m appreciate the benefits and risks to society associated with the use of these cells

Commercial Cells Non rechargeable

Non-rechargeable cells – Zinc-carbon

Standard cell

Short life

2 MnO2 + 2 H+ + Zn + 2 NH3  Mn2O3 + H2O + Zn(NH3)22+

Emf = +1.50 V

Non-rechargeable cells – alkaline

Longer life

MnO2 + H2O + Zn  MnO(OH) + OH- + Zn2+

Emf = +1.60 V

Commercial Cells Rechargeable

Rechargeable cells – Li ion

Rechargeable

Most common rechargeable cell

In use: CoO2 + Li  LiCoO2

Charging: LiCoO2  CoO2 + Li Emf = +3.60 V

Rechargeable cells – lead-acid

Used in sealed car batteries (6 cells giving about 12 V overall)

In use: PbO2 + Pb + 2H2SO4  2PbSO4 + 2H2O

Charging: 2PbSO4 + 2H2O  PbO2 + Pb + 2H2SO4 Emf = +2.04 V

Rechargeable cells – nickel-cadmium

In use: NiO(OH) + 2 H2O + Cd  Ni(OH)2 + Cd(OH)2

Charging: Ni(OH)2 + Cd(OH)2  NiO(OH) + 2 H2O + Cd Emf = +1.40 V

Commercial Cells Fuel Cells

Hydrogen-Oxygen FUEL CELLS

Hydrogen-Oxygen FUEL CELLS

Determine: a) cell emf b) overall reaction

High efficiency (more efficient than burning hydrogen)

How is H2 made?

Input of H2/O2 to replenish so no need to recharge

© www.chemsheets.co.uk A2 1077 2-July-2016

Benefits & risks of using cells

© www.chemsheets.co.uk A2 1077 2-July-2016

Pros & cons of cells

+ portable source of electricity

Pros & cons of non-rechargeable cells

+ cheap, small

– waste issues

Pros & cons of rechargeable cells

+ less waste, cheaper in long run

– still some waste issues

Pros & cons of fuel cells

+ water is only product

– most H2 is made using fossil fuels, fuels cells expensive