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C6 (Hydrogen as fuel, Exothermic and enedothermic, Bond breaking and bond…
C6
Hydrogen as fuel
Combustion of hydrogen is highly exothermic
Uses
Rocket fuel
Fuel cells
Advantages
Very energy rich
No pollutants are formed
Nitrogen oxides not formed (environmentally harmful i.e. acid rain)
Disadvantages
Expensive to product
Difficult (and expensive) to store
Hydrogen fuel cells
Fuel (containing hydrogen) is supplied to anode and air (containing oxygen) is supplied to cathode
Anode
Hydrogen molecules lose electrons to form ions in electrolyte
Cathode
Oxygen gains electrons
Ions formed react to produce water
Exothermic and enedothermic
Exothermic
Reactions that release heat
Chem energy of reactants larger than products
Endothermic
Reactions absorb heat
Chem energy fo reactants smaller than products
Activation energy
Minimum quantity of energy reacting species must possess in order to undergo specified rxn
Bond breaking and bond making
Bond breaking
Endothermic process
Energy must be "taken in" to break bonds apart
Bond making
Exothermic process
Heat is released when this happens
Radioisotopes
Radioisotopes as a source of energy
isotopes that have unstable atomic nucleus and emit energy and particles when it changes to a more stable form
Over 13% of world's electricity is generated from uranium in nuclear reactors
Nuclear energy has long-term nature (sutainable