# Question ccabc

Jun 21, 2016

$4.63 \cdot {10}^{-} 20$ gram

#### Explanation:

You can get to the answer in two steps:

1. calculate: 500 atoms = $\textcolor{red}{x}$ mol ?
2. calculate: $\textcolor{red}{x}$ mol = color(red)? grams,
using the atomic mass of Iron.

Step 1
Avogadro's constant says that $1$ mole of any atom contains $6.022 \cdot {10}^{23}$ 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" = $8.30 \cdot {10}^{-} 22 m o l$

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"# = $4.63 \cdot {10}^{-} 20 g$

So the 500 iron atoms weigh $\textcolor{red}{4.63 \cdot {10}^{-} 20} \textcolor{red}{\text{grams}}$.