Make penny into silver or gold gold

Discussion in 'Chemistry' started by timojin, Feb 23, 2017.

  1. timojin Valued Senior Member

    Turn your pennies into “gold”
    Enjoy chemistry

    Rosemarie Pittenger, a science teacher at John P. Stevens High School in Edison, N.J., made the most of her pennies with this lab demonstration of metallurgy and surface science. To make the silver-looking pennies, Pittenger placed coins in a bath of 1 M zinc chloride solution with small lumps of zinc. Zinc ions floating in the solution grabbed electrons from copper metal on the penny’s surface. This electron exchange produced copper ions that were released into solution and zinc metal that plated the penny with a thin silverlike surface coating. To make the golden penny, Pittenger put one of the zinc-coated coins on a hot plate for a minute or so. The heat made the zinc coating and remaining copper underneath diffuse into each other and mix to form an alloy, specifically yellow brass.
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  3. exchemist Valued Senior Member

    Can you provide a link to this article? I'm struggling, as my recollection is that Zn has a more -ve electrode potential than Cu and so I am not sure I would have expected this to happen. I think I would have expected Zn to reduce Cu ions rather than the other way round, as described here.
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  5. exchemist Valued Senior Member

    Got it. I've looked this up. The trick is that you need Zn metal pieces in contact with the pennies. That way electrons can flow by conduction from Zn to Cu, so that Zn2+ions released into solution (which occurs more readily than release of Cu2+ ions due to the differences in electrochemical potential) can be balanced by electrons flowing from the Zn to the Cu. The Cu thus acquires a -ve charge, allowing it to become a cathode for the Zn 2+ ions in solution to discharge and deposit.

    So it is a kind of disguised electrochemical cell.
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  7. dumbest man on earth Real Eyes Realize Real Lies Valued Senior Member

    ...appears to be copy/pasted from :

    ...simple Chemistry, as exchemist alluded to...

    See also :
    - Steve Spangler - "How to Make Gold Pennies" -
    - " Turning copper coins into 'silver' and 'gold' " -

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