July 01, 2022, 07:49:51 PM
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Topic: Batteries/Volta/Crown of cups/Why copper makes bubble in vinegar and not zinc?  (Read 2703 times)

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Offline Ghemist95

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I was watching a video which explains how the first battery, the voltaic pile, was thought. The video starts with the host showing that if you put zinc in vinegar it starts to create bubbles and starts dissolving. Even though my bad chemistry background I quite understood the process involved in this phenomenon/reaction. Vinegar has hydrogen ions which requests electrons from the zinc who is happy to give them, so the zinc starts to dissolves while hydrogen ions are transformed into hydrogen gas and bubble are fromed. This is the short easy story that suits perfectly for my chemistry level. After this first experiment, the host proceed with the video showing that if you attached the zinc to a piece of copper though a conductor and again immerge both the the zinc and the copper in vinegar, now bubbles start to form around the copper and not around the zinc. Why is that so? Why the zinc doesn't give his electrons immediately right to the hydrogen ions in the vinegar (as before) but instead it passes them through a conductor to the copper which indeed pass them to hydrogen ions. I hope I made my doubts clear , I'm really craving for some help. 
Link to the video:https://www.youtube.com/watch?v=8jlMuBn6Zow&t=29s

Offline Borek

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TBH, I don't like how this video starts, I think it is unnecessarily confusing by ignoring what is really happening.

It is not like the gas stopped evolving on the zinc, quite the opposite. In the background you can still see the gas bubbling on the zinc, only a tiny part of the gas evolves on the copper.
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Offline Ghemist95

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Hi Borek!
Thank you for answering! After you hinted me about it, I went back to the video and effectively seems like the zinc is still froming bubbles too. Anyway I don't see why copper starts to form bubbles too. What makes the electrons flow from the zinc to the copper instead of simply forming bubbles only around the zinc? I don't get it

Offline Arkcon

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You can try this for yourself.  You know that copper in vinegar won't bubble, even slightly.  But does touching zinc to copper cause it to be attacked by vinegar? 
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline Ghemist95

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Hi!
I didn't really understand. I want to underline that mychemistry background is really bad. The information that I provided are all the result of researching andasking on socials. I started really from zero.

Offline Borek

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What makes the electrons flow from the zinc to the copper instead of simply forming bubbles only around the zinc? I don't get it

In metals electrons occupy so called conduction band - they are free to roam through the solid, they are not localized on their atom of origin. Thus, if the metal contains electrons eager to react, they can react wherever they find a right spot on the surface. Actually as electrons are indistinguishable we can't know where (which atom) the reacting electrons come form - and it doesn't matter. What matters is that per each two electrons reducing hydrogen, one Zn atoms leaves the surface as Zn2+ ion.
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Offline Ghemist95

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What would happen if the piece of zinc and the piece fo vinegar were immerged in vinegar  different glasses and connected with a very long conductor? Would the electrons still travel from zinc to copper, and so would the copper dissolve too?

Offline Enthalpy

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If you suggest a current flowing through an open circuit, it's no. Not a DC current. It needs a closed circuit, for instance through an electrolyte and a contact between two electrodes.

Said closed circuit isn't always easy to see, though. It can occur between the crystals and the intercrystalline phase of an alloy in an electrolyte. This is said to accelerate corrosion.

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