Question

What is the total negative charge, in coulombs, of all the electrons in a small 1.20 g sphere of carbon? One mole of C is 12.0g, and each atom contains 6 protons and 6 electrons.

Attempted to calculate the total number of electrons first and then using that to calculate the total negative charge. Came out with 8475.4, but MP says it is wrong.

Answer 1

-57792 C

Step-by-step explanation:

Recall that in one mole of a substance there are an Avogadro number of molecules. That is:

`6.02\,\,\,10^(23)` molecules

therefore, in 1.2 g, there would be ten times less molecules than in the 12.0 g mole, that is:
`6.02\,\,\,10^(22)` molecules.

Now, each C there are 6 negative charges, then, the number of electrons will be six times the number of C molecules, that is:

`6\,*\,6.02\,\,\,10^(23)=36.12\,\,\,10^(22) =3.612\,\,\,10^(23)` electrons.

Now we multiply this number times the charge of an electron
`(1.6\,\,\,10^(-19)\,C)`, and we obtained the total negative charge of the carbon sample:

Total negative charge is:
`5.7792\,\,10^(4)\,C=57792\,\,C`

therefore the total negative charge is: -57792 C