1. The SDN iPhone App is back and free through November! Get it today and please post a review on the App Store!
    Dismiss Notice
  2. Dismiss Notice
Dismiss Notice

Interview Feedback: Visit Interview Feedback to view and submit interview information.

Interviewing Masterclass: Free masterclass on interviewing from SDN and Medical College of Georgia

salt bridge? and galvanic cell ?

Discussion in 'MCAT Study Question Q&A' started by imapremed, Jul 22, 2011.

  1. imapremed

    2+ Year Member

    Joined:
    Mar 16, 2010
    Messages:
    136
    Likes Received:
    0
    Status:
    Pre-Medical
    so i know that you don't need a salt bridge for electrolytic cells but for galvanic cells... its only the salt that is in the salt bridge that is moving right?

    like you won't have extra salts in the solution that go through the salt bridge to even out the charges would you? like instead of having Na+ and Cl- from the SALT bridge, you have NH4+ from one of your solutions traveling through the salt bridge to the other side to even out the charges... that ever occur?
     
  2. Note: SDN Members do not see this ad.

  3. TieuBachHo

    7+ Year Member

    Joined:
    Jul 23, 2008
    Messages:
    212
    Likes Received:
    0
    I think you might be confusing 'bout the mechanism of how gal./ele. cell works. No solution goes through the salt bridge, the salt moves down to stablize the charges while the cell provides electricity in a spontaneous reaction. In an electrolytic cell, it happens agaist its potentials in a non-spontaneous way. So you need a source to overcome this. I am not sure what you are trying to ask.
     
  4. zwander

    7+ Year Member

    Joined:
    May 12, 2010
    Messages:
    344
    Likes Received:
    0
    Status:
    Pre-Medical
    Wait...is that true electrolytic cells don't need salt bridges? And if so why!?
     
  5. TieuBachHo

    7+ Year Member

    Joined:
    Jul 23, 2008
    Messages:
    212
    Likes Received:
    0
    Yes, it doesn't need a salt bridge but it has a solution to accommodate for the charges. It has an "outside source" to drive the rxn. Without this, it wouldn't happen at all due the nature of its potentials. Electrical charges go from high to low but the reverse of the placement of the source's potentials allows this to happen.
     
  6. imapremed

    2+ Year Member

    Joined:
    Mar 16, 2010
    Messages:
    136
    Likes Received:
    0
    Status:
    Pre-Medical
    thanks everyone.

    i found out what i was looking for somehow in br as i read along. the only thing that i was questioning was a question from my reminiscing ap chem days when i remmebred i got a question wrong because NH4+ was used as a specatator ion and theoretically it could be travel through the salt bridge and even out the charge difference... but the only problem was that the bridge's sieves were too small - so NH4+ could not cross the other side.

    but it should be noted i think that you need to even the charge on both sides.. so that anions go to the anode and cations go to the cathode to balence out charge.
     
  7. TieuBachHo

    7+ Year Member

    Joined:
    Jul 23, 2008
    Messages:
    212
    Likes Received:
    0
    The salt bridge is make of fairly inert electrolytes, so they won't react with the sol. Their job is to neutralize the sol. charges so more electrons can travel from one side to the other; thus it prevents the backlog of charges.

    The other one you are talking about is a pourous membrane (not a salt bridge) that allows ions to cross the barrier. Yes, if the sieves are too small, ions can't cross over to relieve the charges build up, then the electrons sieze to flow.
     
  8. darkhope

    10+ Year Member

    Joined:
    Dec 29, 2006
    Messages:
    287
    Likes Received:
    3
    Wait...sorry I'm confused, I thought nothing is moving in the salt bridges besides the distribution of electrons to balance the cells? So electrons shift within the salt bridges, right? or am i completely wrong
     
  9. cheesier

    2+ Year Member

    Joined:
    Jul 17, 2010
    Messages:
    330
    Likes Received:
    3
    Status:
    Pre-Medical
    Ions from the salt bridge go into solution to balance the charges. Electrons don't move through the salt bridge; they move between the anode and the cathode.
     

Share This Page