fuel cells Flashcards
(20 cards)
a chemical reaction gives out more energy when bonds are made it takes in to break bonds. what sort of reaction is it?
exothermic
what is a endothermic process
breaking a chemical bonds require energy
how would you know if a reaction is endothermic
more energy is required to break bonds that is realeased when bonds are formed
how would you know if a reaction is exothermic
if more energy is released when bonds are formed than is needed to break bonds
how can the amount of energy produced in a chemical reaction in a solution be measured
by mixing the reactants in a insulted container, this enables the temperature change to be measured before heat is lost to the surroundings
what is the equation for energy change in terms of bond energies
sum of bonds broken - sum of bonds made
how can a simple cell be made
placing 2 different metals into a beaker containing an electrolyte
what is a cell
composed with 2 electrodes dipped in an electrolyte. it produces electricity from a chemical reaction
what is a battery
2 or more cells connected together in series
what is the voltage produced by a cell dependent on
type of electrode and electrolyte used
state the advantage and disadvantage of using cells and batteries
+: some are rechargeable
-: harmful chemicals
describe rechargeable and non-rechargeable cells
rechargeable- chemical reactions are reversed when an external current is supplied
non-rechargeable- reactants are used up, can’t be recharged
what is a fuel cell
supplied by fuel and oxygen to oxidise the fuel to generate electricity
give the equation for the chemical reaction which takes place at the anode of hydrogen fuel cell
hydrogen lose electrons to form hydrogen ions
2H2—-> 4H+ +4e-
give the equation for the chemical reaction which takes place at the cathode of hydrogen fuel cell
oxygen is added at the cathode, hydrogen ions react with oxygen to form water
O2 + 4H+ +4e- —–>2H20
what is the overall equation for the reaction in the hydrogen fuel cell
2H2 + O2 —->2H2O
what are advantages of hydrogen fuel cells over traditional ways of producing electricity
very efficient, non polluting, very reliable, light weight, have no moving parts
what are disadvantages of hydrogen fuel cells
flammable, toxic chemicals, H2 is difficult to store
why can rechargeable batteries be recharged
the chemical reactions can be reversed
what is the main difference between a fuel cell and a battery
a fuel cell fuel and oxygen has to continuously be supplied
