Pence Copper
How do I find the charge of a 3.1g copper penny that is electrically neutral?
How do I find the charge of a 3.1g copper penny that is electrically neutral? I need both the positive and negative charges. Where do I even start?
I meant by charge the total positive and total negative charges
Well the book told me it is 1.36*10^5C and 1.36*10^-5C so obviously you guys are all wrong. I need to know how to calculate this value…
Zero
No we are not “all wrong”. You forgot to state your question correctly. And, looking at your “answers”, you forgot to state those correctly too. The correct answer is +1.36*10^(+5) Coulombs worth of protons AND -1.36*10^(+5) Coulombs worth of electrons. Learn to put your signs in the proper place.
Method to calculate:
Given mass: m = 3.1 grams
Assuming the penny is entirely copper (which btw, today pure copper pennies are no longer), we divide by the molar mass (M) of copper. This gives the number of moles n.
n = m/M
Now, multiply by Avogadro’s number, N_A to get total number of atoms:
N = n*N_A
N = N_A*m/M
Now, multiply by the atomic number Z of copper. This is the number of protons per atom by definition.
N_protons = Z*N_A*m/M
Multiply by e, the elementary charge, which is the charge of each proton:
q_protons = Z*e*N_A*m/M
Negate to get charge of electrons:
q_electrons = -q_protons
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