Chemistry - Redox

Galvanic cells applications

• Primary cell ‘leclanche”

• Secondary cell “Lead acid accumulator”

• Hydrogen oxygen fuel cell

Advantages disadvantages and uses of hydrogen fuel cell

Advantages

• High efficiency of energy conversion as compared to internal combustion engine

• Continuously generate electricity as long as reactants are supplied

• Green chem (clean energy) - produced only water as a byproduct when using hydrogen as fuel

Disadvantages

• Expensive

• bulky

Uses

• Motor vehicles

• Portable power generation

oxygen is always the _______ in a fuel cell

oxidant/oxidising agent

purpose of porous electrodes in hydrogen oxygen fuel cell 

• coated with platinum catalyst 

• allows gases to come into contact with ions in the electrolyte 

• reduction and oxidation reactions occur on the surface of the electrode 

Standard reduction potential measures?

• The relative tendency of a species to be reduced

• Measured using the standard hydrogen half cell as a reference cell

Conditions for corrosion

• Metal surface free from protective films

• Suitable oxidising agent, o2

• Solution containing ions for conducting charge, h2o

Products of corrosion 

Soluble: readily dissolved and washed away leaving holes or pits in the metal 

Sparingly soluble: forms layers which are not washed away 

• Incoherent - Flaky, powdery or peel off the metal surface, oxidation of Fe

• Coherent - stay in one piece to form a continuous coating of the metal surface