Electrode potentials Flashcards
What reactions happen in an electrochemical cell
Redox
Explain a Zn/Cu electrochemical cell
Zn = more -ve = gets oxidised Zn looses electrons forming Zn2+ Electrons travel around the external circuit to the Cu electrode Cu2+ = more +ve = get reduced Cu gains 2 electrons to form Cu
How do u measure the voltage in a electrochemical cell
Insert a voltmètre
Why is pt used as electrodes
Inert
Conducts electricity
What are the half equation for a Zn/Cu cell
Zn -> zn2+ + 2e-
Cu2+ + 2e -> Cu
What is the equation for electrode potential
Electrode potential = reduced - oxidised
Define standard electrode potential
The voltage measured under standard conditions connected to a standard h electrode
What are standard conditions
289k
100kpa
Solutions all have a conc of 1.00 moldm-3
What electrode potential do standard h electrodes have
0.0V
What side are standard h electrodes always on
Left
Which side of the cell does the reduces species go
Right
Which side of the cell does the oxidised element go
Left
What factors affect electrode potentials
Temp
Pressure
Conc
As they effect the position of eqm
Why are standard conditions used
Always get the same value for electrode potentials
Can compare with different cells
What electrode potentials do very reactive metals have and why
More negative
More readily looses electrons (gets oxidised)
What wlectode potential do very reactive non metals have
More positive
More readily wants to gain electrons (gets reduced)
When are productions about the electrode potentials wrong
Changing the conc or temp of solution
The rate of reaction may be so slow it looks like nothing is Happening
The reaction has a high activation energy
What is the equation at the anode of a oxygen hydrogen fuel cell
H2 -> 2H+ + 2e-
What is the half equation at the cathode for a oxygen hydrogen fuel cell
0.5O2 + 2H+ + 2e- -> H2O
What is the structure between the anode and cathode in a hydrogen oxygen fuel cell
Polymer electrolyte membrane
What is the fuel in a hydrogen oxygen fuel cell
H2
What is the oxidant in the hydrogen oxygen fuel cell
O2
What is the function of the polymer electrolyte membrane
Only permeable to H+
Forcing e- to travel around the circuit to the cathode
What catalyst is used a hydrogen oxygen fuel cell
Pt
What is the waste product of a hydrogen oxygen fuel cell
H2O
Explain how a hydrogen oxygen fuel cell works
- Anode = pt catalyst splits the H2 into protons and electrons
- The polymer electrolyte membrane only allows h+ to pass to the cathode forcing e- around the external circuit to the cathode
- An electric current is created by the flow of electrons in the external circuit
- Cathode = o2 combines with h+ (from anode) and e- (from circuit) to make H2O
What are the befits of fuel cells
More efficient than combustion = energy isn’t wasted as heat
Produce less pollution = only produce H2O not CO2
What are the negatives of fuel cells
The production of them needs a toxic chemicals which needs to be disposed of
The toxic chemicals are vey flammable. So if there’s a fault it will catch fire
What is the danger of using lithium in batteries
High reactive ans flammable
If there’s a fiant it will catch on fire
