Ch 9 Flashcards
What is dry corrosion
Direct reaction with oxygen from the air forming a metal , oxide
Wet corrosion
Moisture accelerating the process of corrosion eg production of rust from iron reacting with rain or moisture in the air over time
Why does iron in costal areas corrode faster?
The presence of Na+ ions in the water increases it’s conductivity thus increasing rate of corrosion
How can you prevent corrosion
1 surface protection
Paint, plastic, oil or grease can be used to coat iron and prevent oxygen and water from reaching it
2 electrochemical protection
cathodic protection
Using a direct current power supply to maintain negatively charged iron thus stoping iron from oxidising (becomes the oxidising agent)
Sacrificial protection
Coating iron in metal such as zinc which will corrode instead of the iron itself
(Galvanised iron)
Applications of fuel cells
Vehicles/transport
Power generation for heating and electricity in homes
Advantages of fuel cells
1converts chemical energy directly into electrical energy which is more efficient than other energy sources like fossil fuels
2in hydrogen fuel cells only water and heat is produced no harmful greenhouse gases
3can use a variety of fuels
4hydrogen is very abundant
Disadvantages of fuel cells
1Require a constant fuel supply
2matirials needed to build them eg platinum electrodes are expensive
3 new technology therefore infrastructure needed isn’t implemented yet eg network of hydrogen filling stations for use as fuel for vehicles
4 sourcing hydrogen uses lots of energy
5storing hydrogen fuel is costly and dangerous due to explosive tendencies
what is the potential difference of half cell?
The tendancy of one cell to be an oxidising agent and the other to be a reducing agent, causing electrons to migrate across a wire.
what are primary cells
non-rechargable because the products migrate away from the electrodes or are consumed by side reactions in the cell, preventing reverse reactions. when the cell reaches equilibrium the flow of electrons stop
what are secondary cells
rechargeable cells because products are converted back into reactants when a potential difference is created by an external energy source (charger) which turns the cell into an electrolytic cell.