Calculating Charge Lost from a 3.0-g Copper Penny

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To determine the fraction of electrons lost from a 3.0-g copper penny with a positive charge of 67 mC, the correct approach involves calculating the total number of electrons in the penny and the number of electrons corresponding to the charge. The initial calculation of total electrons was incorrect, but a revised approach yielded approximately 8.2 x 10^23 electrons. The charge of 67 mC translates to about 4.2 x 10^14 electrons lost. Dividing the number of lost electrons by the total gives a fraction of approximately 5.1 x 10^-10, indicating a very small fraction of electrons lost.
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Homework Statement


A 3.0-g copper penny has a positive charge of 67 mC.
What fraction of its electrons has it lost?

Homework Equations


I don't think I am donig this right. i need guidance

The Attempt at a Solution


i take 3.0 grams * 63.5amu * 6.022 * 10^23 * 29 (electrons) = 3.3*10 ^ 27

67 * 10^-6C / 1.6 * 10 ^ -19C = 4.2 * 10^14

3.3*10 ^ 27/4.2 * 10^14 = WRONG ANSWER. HELP!
 
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gillyr2 said:

Homework Statement


A 3.0-g copper penny has a positive charge of 67 mC.
What fraction of its electrons has it lost?


Homework Equations


I don't think I am donig this right. i need guidance


The Attempt at a Solution


i take 3.0 grams * 63.5amu * 6.022 * 10^23 * 29 (electrons) = 3.3*10 ^ 27

67 * 10^-6C / 1.6 * 10 ^ -19C = 4.2 * 10^14

3.3*10 ^ 27/4.2 * 10^14 = WRONG ANSWER. HELP!

A mole of copper atoms will weigh 63.54 grams. 3 grams is what portion of the mole? Then you can go wild with Avogadro and all the orbiting electrons.
 
ok. would this be correct?

3.0 grams / 63.5amu * 6.022 * 10^23 * 29 (electrons) = 8.2 *10^23

67 * 10^-6C / 1.6 * 10 ^ -19C = 4.2 * 10^14

(4.2 * 10^14)/(8.2 * 10^23) = 5.1*10^-10

Is this correct?
 
gillyr2 said:
ok. would this be correct?

3.0 grams / 63.5amu * 6.022 * 10^23 * 29 (electrons) = 8.2 *10^23

67 * 10^-6C / 1.6 * 10 ^ -19C = 4.2 * 10^14

(4.2 * 10^14)/(8.2 * 10^23) = 5.1*10^-10

Is this correct?

That looks more better as far as your method. I didn't check your math.
 

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