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Teacher asks why penny turns green in bleach
Q. I am putting together a simple experiment and I noticed that if I put a penny in bleach and left it over night it turned green. I was curious if you could tell me why.
Thank you, Kelli
teaching - Bloomington, Indiana
2003
A. The copper is reacting with the chlorine in the bleach to form cupric chloride, which is green.
James Totter, CEF
- Tallahassee, Florida
2003
Q. What is the specific chemical formula when bleach and pennies are combined? A friend just recently placed pennies in a glass bottle, filled it with bleach, and screwed on the cap. About a half hour later, the bottle exploded. What caused this? What gas, if any? Thanks, my roommate, friend and I are all very curious.
Amy Perkins- Melbourne, Florida
2004
A. Hi, Amy. Glad that you're only curious and not bloody from the explosion of the bottle. Pennies since 1982 are copper-clad zinc. Bleach is sodium hypochlorite (NaOCl) with a lot of caustic soda
[affil links]
(NaOH) in the solution to keep the bleach alkaline. It derives it's oxidizing power from the reduction of oxygen from +6 to -2.
I haven't worked the exact formula, but the reaction between copper and bleach would release a significant amount of oxygen gas as the NaOCl is transformed to NaCl and O2, with the required electrons for this reaction coming from the oxidation of copper metal to copper ions.
Additionally, once the zinc is exposed, the caustic soda will dissolve it very rapidly, releasing hydrogen gas.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
September 23, 2009
Q. So, I am doing a science fair project and I need to know just would it take longer than 15 minutes in bleach, toilet cleaner, and a couple of other cleaners, filled 1/2 cup with 1 penny in each, for the penny to turn green?
cilest w [last name deleted for privacy by Editor]science fair project - California, USA
February 18, 2012
Hi, Cilest. Ms. Kelli found that the penny turned green overnight. If you were asking whether some particular event would occur in 15 years or 15 months, we would be glad to try to help you; but when you ask whether something will happen within 15 minutes, the answer is that you should be willing to invest 15 minutes to find out :-)
Good luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
February 20, 2012
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