Section 8 - Electrode Potentials and Cells Flashcards
What is an electrochemical cell made from?
Two different metals dipped in salt solutions of their own ions and connected by a wire.
What kind of reaction occurs in an electrochemical cell?
Redox
What is the salt bridge made from and what is its use?
Filter paper soaked in KNO3(aq)
Allows ions to flow and completes the circuit
Which way do electrons flow round a circuit?
From the more reactive metal to the less reactive one
What is the voltage between the two cells called?
Cell potential or EMF
What kind of electrode is used if not the metal of the ions?
Platinum
Is the forward direction of an electrode half equation showing reduction or oxidation?
Reduction
What kind of electrode potential will a metal which is difficult to oxidise have?
Very positive
If an electrode has a more negative electrode potential, will it be reduced or oxidised?
Oxidised
Which half equation needs to be reversed?
The one for oxidation
What are electrode potentials measured against?
Standard hydrogen electrodes
Define Standard Electrode Potential
The voltage measured under standard conditions when the half-cell is connected to a standard hydrogen electrode
What are the standard conditions for measuring electrode potentials?
- solutions have concentrations of 1.00 moldm-3
- 298K
- 100kPa
Where are the best oxidising agents found on an electrochemical series?
Left of the more positive end.
Where are the best reducing agents found on an electrochemical series?
On the right of the more negative end
How do you calculate Standard Cell Potential for two half-cells?
Ecell = Ereduced - Eoxidised
How do you draw an Electrochemical cell?
Reduced Form | Oxidised Form || Oxidised Form | Reduced Form
On which side of an electrochemical cell drawing does the half-cell with the more negative EMF go?
Left
For a feasible reaction, is Ecell positive or negative?
Positive
Are Lithium batteries rechargeable?
Yes
What are the half-equations for the Lithium Cell?
Li+ + e- <–> Li - negative electrode
Li+ + CoO2 + e- <–> Li+[CoO2]- - positive electrode
How are lithium cells recharged?
A current is supplied to force electrons to flow in the opposite direction around the circuit and reverse the reactions.
What are the reactions that occur in an alkaline hydrogen-oxygen fuel cell?
2H2 + 4OH- –> 4H2O + 4e-
O2 + 2H2O + 4e- –> 4e- + 4 OH-
What is the overall equation of alkaline hydrogen-oxygen fuel cell?
2H2 + O2 –> 2H2O
What are 3 advantages of fuel cells?
- more efficient - internal combustion engines lose energy through heat
- only waste product is water
- don’t need to be recharged
Give 2 disadvantages of fuel cells:
- energy required to produce the hydrogen and oxygen - not carbon neutral
- hydrgoen is highly flammable
