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Battery with two half cells

  1. Jan 11, 2007 #1
    1. The problem statement, all variables and given/known data
    I have got a battery with two half cells.

    One cell with.
    A silver rod in a 100 mL AgNO3 0,025 M solution.

    One cell with.
    A zinc rod in a 100 mL Zn(NO3)2 0,150 M solution.

    So my question is what reactions happen?

    And which reaction is the electricity providing one?

    2. Relevant equations
    I do not think that there are any

    3. The attempt at a solution
    My bet

    First cell (with Ag)
    Ag+ + NO3- + e- -> Ag + NO3-

    Second cell (with Zn)
    Zn(NO3)2 -> Zn2+ NO32- but then where are the electrons? Furthermore I think this is the electricity providing one!
  2. jcsd
  3. Jan 11, 2007 #2
    Not to be irritating, but some help would be very appreciated...
  4. Jan 11, 2007 #3
    Homemade batteries are cool to make. This info doesn't really help you but you should also try yo make a hydrogen battery. Its pretty interesting.
  5. Jan 11, 2007 #4
    Well I am afraid (as you said) that piece of information will not prove very usefull...
  6. Jan 11, 2007 #5
    First off, you need to label solids, aqueous or gaseous of the elements & solutions.

    Basic idea: Redox Reactions [reduction & oxidation reactions. LEO says GER, Loss of Electrons = Oxidation. GER = Gain of Electrons = Reduction. You basically have a reaction where there's a loss of electrons and a gain of electrons.

    To cause the loss or gain of these electrons there needs to be reactions taking place that turns these elements into ions.

    Here's some things to think about

    Ag solid silver rod -> What does it want to be and what does it do?
    Zn solid silver rod -> What does it want to be and what does it do?

    Ag Solution -> What is this exactly [*note* you figure out it's charge]?
    Zn Solution -> What is this exactly [*note* you figure out it's charge]?

    How is AgNO3 and Zn(NO3)2 related to both?

    Have a try at the problem again and if not, I'll help you through it.
    Last edited: Jan 11, 2007
  7. Jan 11, 2007 #6


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    Staff Emeritus
    Science Advisor

    In the first equation, you have written Ag+ and NO3- as ions, whereas in the second you have written Zinc Nitrate as a compound. You should stick to writing out the ionic equations.

    Also, in the second equation, you have the charge on the nitrate ion as 2-; this is different to the (correct) ion in the first equation.

    You also seem to be mixing up metal solids and metal ions. Try using state symbols. Do you know how Ag(s) is different to Ag2+(aq)? Try writing the equations again.

    edit: very slow typing from me!
  8. Jan 11, 2007 #7
    Well the main problem is that I know I have to solutions.

    Ag(s)+Ag+(aq)+NO3-(aq) ->

    I have no idea what that will become the same about the zinc where it is.

    Zn(s)+Zn2+(aq)+2NO3-(aq) ->

    That is kind of where I am stuck...
  9. Jan 11, 2007 #8
    Here's a thought: Does the NO3 matter as an ion or a compound? Will it cancel itself out in the end equation?

    Zn ( s ) -> Zn 2+ ( aq ) + 2 e-
    Ag ( s ) -> Ag + ( a ) + 1 e-

    What happens with the net reaction?
  10. Jan 11, 2007 #9
    Well but then what really happens if you put that together you get that
    Zn ( s ) 2Ag(aq)+ -> Zn 2+ ( aq ) + 2Ag(s)
  11. Jan 11, 2007 #10
    That is exactly what happens during the reaction.

    Now tell me. Which one is the anode and which one is the cathode?

    I'll take you through the steps through each post heh.

    Remember, LEO says GER. Anode = oxidation occurs, Cathode = reduction occurs.

    Just a side note->
    Normally, in a cell reaction there is a salt bridge. In which electrons can flow freely between both cells heh.

    I have my college class in about 15 minutes [2 PM PST -> 3:20 PM PST]; so if I don't get to you that's the reason why.
  12. Jan 11, 2007 #11
    Well thank you you have helped enough, you have been very heplful and for that I am most grateful. Thanks a lot!
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