# Which has a greater number of atoms: 3.0 g of iron, Fe, or 2.0 g of sulfur, S?

##### 1 Answer

#### Explanation:

In order to be able to determine how many atoms you have in those two samples, you first need to find how many moles of each element you have here.

As you know, **one mole** of any element contains exactly **Avogadro's number**.

Moreover, en element's *molar mass* will tell you what the mass of one mole of said element is. The idea is that the difference between the mass of *one mole* of iron and *one mole* of sulfur is determined by the difference between the actual atoms of the two elements.

The *heavier* an individual atom is, the **heavier** one mole of such atoms will be.

So, use iron and sulfur's respective molar mass to determine how many moles of each you have

#"For Fe: " 3.0color(red)(cancel(color(black)("g"))) * "1 mole Fe"/(55.845color(red)(cancel(color(black)("g")))) = "0.0537 moles Fe"#

#"For S: " 2.0color(red)(cancel(color(black)("g"))) * "1 mole S"/(32.065color(red)(cancel(color(black)("g")))) = "0.0624 moles S"#

Since you have *more moles* of sulfur, you will also have **more atoms** of sulfur.

More specifically, the two samples will contain

#0.0537color(red)(cancel(color(black)("moles"))) * (6.022 * 10^(23)"atoms of Fe")/(1color(red)(cancel(color(black)("mole")))) = 3.23 * 10^(22)"atoms of Fe"#

and

#0.0624color(red)(cancel(color(black)("moles"))) * (6.022 * 10^(23)"atoms of S")/(1color(red)(cancel(color(black)("mole")))) = 3.76 * 10^(22)"atoms of S"#