Redox is Cringe Flashcards
What is oxidation
Loss of electrons
Gain of oxygen
Loss of hydrogen
What is reduction?
Gain of electrons
Loss of oxygen
Gain of hydrogen
What happens when a rod of a metal is dipped into a solution of its ions?
An equilibrium is set up between the solid metal and aqueous metal ions
What is a simple salt bridge made out of?
Filter paper soaked in a saturated solution of KNO3
At which electrode does reduction take place?
Cathode
At which electrode does oxidation take place?
Anode
What is emf?
The standard electrode potential of a half cell connected to standard hydrogen electrode
What does a positive potential mean?
Substances are more easily reduced and will gain electrons
What does a negative potential mean?
Substances are more easily oxidised and will lose electrons to become more stable
Why are salt bridges necessary ?
They complete the circuit allowing a flow of charge through ion movement. They also contain inert ions so they don’t react with the electrodes.
What conditions are required to use the standard hydrogen electrode?
Temperature- 298K
Pressure - 100 kPa
[H+] - 1M
When would you use a platinum electrode?
When both the oxidised and reduced forms of the metal are in aqueous solution.
what is a fuel cell?
a fuel cell uses the energy from the reaction of a fuel with oxygen to create volatage
why is necessary to use a high resistance voltmeter?
so that they don’t divert much current from the main circuit
what does the positive electrode favour?
reductioj
what does the negative electrode favour/
oxidation
what does increasing the concentration of reactants do to the E cell value?
increase it and vice versa
what is reason why a reaction won’t take place even if the E cell value is positive/
it may have a very high activation energy
what does a negative E° value indicate?
the further the equilibrium lies to the left i.e. the more readily the metal loses electrons to form ions
what does a more positive (or less negative) E° value mean/
the further the equilibrium lies to the right i.e. the less readily the metal loses electrons to form ions
Give two advantages of using fuel cells compared with the combustion of petrol or diesel?
- less CO2 produced overall.
- greater efficiency
Give an advantage of using methanol,rather than hydrogen in a fuel cell for use in cars?
Methanol is a liquid and is therefore easier to store and transport.
What is the essential difference between a fuel cell and conventional electrochemical cell?
-a fuel cell produces electricity by the reaction of a fuel with oxygen
State two ways that hydrogen might be stored as a fuel for use in cars?
- compressed as a gas
- adsorbed onto a solid
