Question

Question #ccabc

Answer 1

`4.63*10^-20` gram

Explanation:

You can get to the answer in two steps:

1. calculate: 500 atoms = `color(red)x` mol ?
   using Avogadro's constant.
2. calculate: `color(red)x` mol = `color(red)?` grams,
   using the atomic mass of Iron.

Step 1
Avogadro's constant says that `1` mole of any atom contains `6.022*10^23` atoms. In this case you have `500` atoms:

`(500 color(red)cancel(color(black)("atoms")))/ (6.022*10^23 color(red)cancel(color(black)("atoms"))/"mol"` = `8.30*10^-22 mol`

Step 2
The atomic mass of iron (Fe) will give you the weight of one mole of this molecule: `1` mol = `55.845` gram:

`55.845 g/(color(red)cancel color(black)"mol") * 8.30*10^-22 color(red)cancel color(black)"mol"` = `4.63*10^-20 g`

So the 500 iron atoms weigh `color(red)(4.63*10^-20) color(red)"grams"`.