# Silver Pin Charged

## Homework Statement

(a). Calculate the number of electrons in a small, electrically neutral silver pin that has a mass of 10g. Silver has 47 electrons per atom, and its molar mass is 107.87 g/mol.
(b). Imagine adding electrons to the pin until the negative charge has the very large value of 1.00 mC. How many electrons are added for every 10^9 electrons already present?

## The Attempt at a Solution

I got the answers for both (a) and (b) (answers in back of book), but I still don't understand how to get (b). Heres my steps:

For (a), all I did was dimensional analysis to find the amount of electrons in 10 g of Ag, whic is about 2.62 x 10^24 e-. For part (b), I am confused, but what I found out how many electrons in 1 mC, which was 6.25 x 10^24 e-, and divided it by 2.62 x 10^24 e-, and I got 2.38 e- for every 10^9 electrons already present, but still this does not make sense to me. Can someone explain it to me or give me some helpful hints?

How many elementary electrical charges are there in one milliCoulomb?

How many elementary electrical charges are there in one milliCoulomb?
6.25 x 10^24 e-... so what do I do with that?

How many groups of 10^9 electrons are there in the silver pin?

2.62 x 10^24 e-/10^9 e-=2.62 x 10^15

So if I divide the number of electrical charges in one milliCoulomb by the number of groups of 10^9 electrons, won't that supply the answer to the question?

why?

It seems to me that's exactly what they are asking for...