# Question 7d116

Oct 5, 2015

$1.19 \cdot {10}^{9} \text{atoms of Fe/red blood cell}$

#### Explanation:

What you need to do here is find how many moles of iron you get in that many grams of iron, then use Avogadro's number to help you find how many atoms of iron you have.

Ion has a molar mass of $\text{55.845 g/mol}$, which means that $\text{2.90 g}$ of iron will contain

2.90color(red)(cancel(color(black)("g Fe"))) * "1 mole Fe"/(55.845color(red)(cancel(color(black)("g Fe")))) = "0.05193 moles Fe"

You know that one mole of any element atoms contains exactly $6.022 \cdot {10}^{23}$ atoms of that element. In your case, one mole of iron will contain $6.022 \cdot {10}^{23}$ moles of iron.

This means that you have

0.05193color(red)(cancel(color(black)("moles Fe"))) * (6.022 * 10^(23)"atoms Fe")/(1color(red)(cancel(color(black)("mole Fe")))) = 3.13 * 10^(22)"atoms Fe"

Since you know that you have about $2.64 \cdot {10}^{- 13}$ red blood cells tha contain this many atoms of iron, which means that you get an average of

(3.13 * 10^(22)color(red)(cancel(color(black)("atoms Fe"))))/(2.64 * 10^(-13)"red blood cells") = color(green)(1.19 * 10^9"atoms Fe/cell"#

The answer is rounded to three sig figs.