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Electrochemistry

Discussion in 'MCAT Study Question Q&A' started by Sonyfan08, Aug 18, 2011.

  1. Sonyfan08

    7+ Year Member

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    I just realized I never really went over electrochemistry & my test is tomorrow. I know, fail on my part.. what do I need to know about electrochemistry for the MCAT?
     
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  3. dancerdoc89

    dancerdoc89 Knowledge is Power

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    This is what I would know:

    -general set up of galvinic and electrolytic cells
    -sign designations of galv/electro cells for the anode and cathode
    -which way electrons flow
    -how to calculate cell potential from individual reduction potentials from provided half-reactions
    -the directions in which the ions in a salt bridge flow
    -the Nernst equation
    -are galv/electro cells are spont. or nonspont.?
    -is the overall cell potential of a galv/electro cell positive or negative?
    -know what the term reduction potential means

    This is what I can think of off the top of my head. Best of luck:xf:
     
  4. docmayer

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    That's pretty much all you need to know, and it really isn't that much..Just read the chapter and do whatever problems you have available to you.
     
  5. Sonyfan08

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    Thanks guys!
     
  6. MT Headed

    MT Headed snow, PBR, and bears
    Lifetime Donor Classifieds Approved 2+ Year Member

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    And for the love of God, know that the anode is where oxidation takes place. Always. By definition. In every scenario. Anode=Oxidation. That knowledge alone, plus 20 minutes of extra time, will solve 99% of MCAT electrochemistry problems.
     
  7. plzNOCarribbean

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    for galvanic cells, the cell potential is positive and for electrochemical cells, cell potential is negative. This is why reactions occur spontaneously with galvanic cells, and non-spontaneous with voltaic cells, which is why a battery is required.

    This is based off the equation dG= - nFEcell

    where n= moles of electrons, F-Faradays constant, and E cell is the cell potential. Also, you should note, unlike the individual half reaction potentials and cell potential, the total energy (or the amount of work that the cell can do is proportional to both the number of moles of electrons and the cell potential)

    -sign designations of galv/electro cells for the anode and cathode
    -which way electrons flow

    ^ a little confused about this one myself, so someone help me out. Electrons ALWAYS flow from the anode to the cathode, right? But in galvanic cells, that anode is the (- electrode) and the cathode is the (+), right? and in Electrolytic* cells, its just flipped (anode=+ , cathode=-, except electrons still move from anode to the cathode) right?
     
    #6 plzNOCarribbean, Aug 19, 2011
    Last edited: Aug 20, 2011
  8. PingPongPro

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    Electrons flow from the anode to the cathode. Just remember OXIDATION always occurs at the anode (lose electrons at anode) and REDUCTION at the cathode (gains electrons).

    Your confusion I think lies with the different ways the different subjects defines/looks at things. I remember I was kinda confused when I first learned it, but physicists and biochemists refer to different things when talking about a battery. Like in physics, the negatively charged electrons travel to the positive cathode. But in biochem, the negatively charged compound travels to the anode. Like wtf right? Its because they are looking with different perspectives at different parts of the battery. Its probably not TOO important to labor over this, but just know this difference exists.

    Just remember oxidation occurs at anode lol.

    The OP probably won't see this, but oh well.
     

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