BME 221 - Lecture 12/1/14
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Explain why lithium is a popular choice as a metal to make a battery? Note what the significance of lithium will be in a battery
Lithium is easily oxidized, has a large negative reduction potential, likely to give off e- (alkaline metal).
Describe the Daniell Zn-Cu Electrochemical Cell
In the electrochemical cell above, zinc will be consumed and copper will form on the electrode.This is the principle of electroplating. In one of the half cells reduction happens and in the otherone oxidation occurs. The salt bridge connects the two solutions to complete the circuit loop; itusually contains agar with high concentration of relatively inert salts in the respective electrochemicalcell, such as KNO3.
How can you change the electrochemical potential (no longer standard, i.e. 1.1V for Zn-Cu) with only a Daniell cell and water?
By changing the concentrationof the ions, you can actually change the electrochemical potential. If you increase the concentrationof the ion (Cu2+) on the reactant side or decrease the concentration of the ion (Zn2+) on theproduct side, you can increase the electrochemical chemical and vice versa.
where oxidation happens
where reduction happens
The cells mentioned above converts chemical energy to electrical energy.
electrolytic cells, purpose and significance
for some reactions, you can drive non-spontaneous reactions forward byconnecting this cell to an external power supply, in the reverse direction. You will need to applyat least the voltage that the natural electrical potential of the battery.
Describe electrolytic cells:
Anode is connected to the plus pole and cathode is connected to the minus pole of the external power supply.
one-line writing convention of Galvanic cells
Zn(s)|ZnSO4(aq, 1M)||CuSO4(aq, 1M)|Cu(s). A single vertical line means a phase separation; the double vertical line means the salt bridge.
Standard Hydrogen Potential
- Single-Electrode Potential
- H+ + e− <-->1/2H2(g).
- The simplest electrode is the standard hydrogen electrode (SHE).
- By convention, the standard electrode potential for SHE is 0.00V
What does it mean if a half-cell has a higher positive standard potential?
it is a stronger oxidizing agent (F2, +2.87V)
What does it mean if a half-cell has a higher negative standard potential?
it is a stronger reducing agent (Li+, −3.05 V)
What would you like to do?
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