3.1.11 Electrode Potentials Flashcards
Label the diagram of the standard hydrogen fuel cell
What are the standard conditions for measuring an electrode potential
- Temp = 298K
- All concentrations = 1moldm-3
- All pressures = 100kPa
The standard hydrogen electrode is always placed on the left. How is it represented in standard cell notation (conventional cell representation)
Why does this half cell need a platinum electrode?
Because Fe2+ and Fe3+ are both aqueous solutions
Why is platinum a suitable electrode for use in cells that do not have a solid conductor in their half equation?
Pt is unreactive AND conducts electricity
Why is KNO3 a suitable solution for a salt bridge?
KNO3 is unreactive with the electrodes AND the ions are free to move
Why might the current produced by a cell fall to zero after some time?
All the reactants are used up
What will happen to a cell once the reactants are used up?
Stops working OR starts to leak
How do you work out the strongest oxidising and reducing agents using SOWR?
Find the most positive electrode value and write SOWR
What is the equation to calculate emf/Ecell/voltage of a cell?
What are the three most important words to help you with the Electrodes topic
Positive
Right
Reduced
Give an environmental advantage of using rechargeable cells.
Metals are reused.
Give an environmental disadvantage of using rechargeable cells
Mains electricity is used to recharge, which may come from combusting fossil fuels, which releases CO2(g)
Why does the standard hydrogen electrode have a voltage of 0 volts?
By definition
What is the half equation that occurs at the negative electrode of a Lithium Ion rechargeable cell
Li –> Li+ + e-
What is the half equation that occurs at the positive electrode of a Lithium Ion rechargeable cell
CoO2 + Li+ + e- –> Li(CoO2)
(Oxidation state of Co goes from +4 to +3)
What is the conventional cell notation for a Lithium Ion cell?
Why does a fuel cell not need to be electrically recharged
Because the reactants are supplied continuously
Suggest one advantage of using methanol, rather than hydrogen, in a fuel cell for use in cars.
Methanol is liquid so can be stored and transported easily
Suggest why the EMF values of the acidic and alkaline hydrogen–oxygen fuel cells are the same
They have the same overall reaction
2 H2 + O2 → 2 H2O
What is the half equation for the reaction that occurs at the positive electrode of a hydrogen fuel cell in alkali conditions
O2(g) + 2 H2O(l) + 4 e– → 4 OH–(aq)
What is the half equation for the reaction that occurs at the positive electrode of a hydrogen fuel cell in acid conditions
O2(g) + 4H+ + 4 e– → 2H2O(aq)
What is the half equation for the reaction that occurs at the negative electrode of a hydrogen fuel cell in alkali conditions
H2 + 2OH- → 2H2O + 2e-
What is the half equation for the reaction that occurs at the negative electrode of a hydrogen fuel cell in acid conditions
H2 → 2H+ + 2e-
Complete the diagram to show how the e.m.f. of a hydrogen–oxygen fuel cell changes with time.
State the main environmental advantage of using a hydrogen–oxygen fuel cell to power a car.
Water is the only product
Suggest why the use of a hydrogen–oxygen fuel cell might not be carbon-neutral.
CO2 is released because fossil fuels are burned to produce electricity to generate hydrogen
