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Topic: formulas and copper  (Read 7571 times)

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formulas and copper
« on: April 24, 2004, 08:58:58 PM »
 ???   I tried answering the questions 7 times and every time I got it back because it was wrong

             yields what?  

with copper: when pennies are heated, what happens     to the copper atoms and how could the pennies be converted to ordinary coins? (when it is heated, the pennies changed to the colors silver and gold)

also, when copper powder is heated, it turned into a black ash-like substance. Why did the mass increase?

[Edit: added some subscripts & corrected spelling for easier reading]
« Last Edit: April 25, 2004, 01:44:40 AM by hmx9123 »

Offline Mitch

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Re:formulas and copper
« Reply #1 on: April 25, 2004, 01:06:17 AM »
the mass increased because atmospheric oxygen made an oxide with the chemicals in the pennies.
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Offline hmx9123

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Re:formulas and copper
« Reply #2 on: April 25, 2004, 01:55:09 AM »
First, why don't you give a try with your first part of your question to the organic forum.  People will be more likely to respond to it there.

For the second part of your question, here's what happens:

2 Cu + O2 --> 2 CuO

The elemental copper powder reacts with the oxygen in the air to form copper (II) oxide.  I say copper (II) oxide because copper (I) oxide is red and you describe a black substance.  Copper (II) oxide is black.  

Now, when heating pennies, ordinarily, you just get the reaction above.  However, with the color change you're talking about, you have to first soak the penny in a solution of concentrated NaOH and Zn, to form the sodium zincate complex:


This complex forms on the outside of the penny, and when you heat it, the copper and the zincate complex combine to form brass, which is the shiny silvery/gold color.  It's pretty cool, actually.
« Last Edit: April 25, 2004, 01:55:36 AM by hmx9123 »

Offline AWK

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Re:formulas and copper
« Reply #3 on: April 25, 2004, 03:48:27 AM »
methyl salicylate (or hydroxybenzoate)
Depending on temperature, time and amount of concentrated sulfuric acids other products also can be formed

Depending on temperature of heating copper may form CuO or Cu2O

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