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Thread: Half Cells

  1. #1 Half Cells 
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    I was lookng up this programme that teaches half cells.

    i came across the following passage and it doesnt make sense to me
    hopefully someone can help me out

    it writes
    If a standardy hydrogen half cell is connected to a standard zinc cell. the reading on the high resistance voltmeter will be -0.76. a negative electrode potential means the hydrogen half cell is acting as an electron acceptor. i get that part

    electrons flow from the zinc cell to the hydrogen cell. i get that part

    the more negative the electrode potential the stronger the reduced species (here Zn) is an electron donor.

    my problem is i can't see why Zn is the reduced species.

    Zn -----> Zn2+ + 2e-

    it seems to me that the zinc has been oxidised here not lost.
    do you think it means reducing species. like reducing agent?
    or maybe i have just missed something obvious.


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  3. #2  
    Forum Sophomore Matt Lacey's Avatar
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    In the system, the zinc metal is the reduced species and Zn<sup>2+</sup> is the oxidised species. Same goes for the hydrogen, H<sup>+</sup> is the oxidised species and H<sub>2</sub> is the reduced species.

    It's simply because of the difference of the Zn<sup>0</sup> and Zn<sup>2+</sup> species.

    Hope that's clear...


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  4. #3  
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    oh so does that mean Zn is like the reduced form?

    of the reaction Zn2+ + 2e- -----> Zn
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  5. #4  
    Forum Sophomore Matt Lacey's Avatar
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    Yeah, that's basically it. Zn is the reduced species in that half reaction and in the overall (forward) reaction...

    Zn + 2H<sup>+</sup> --> Zn<sup>2+</sup> + H<sub>2</sub>
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  6. #5  
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    cheers dude thats really helpful
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