3. How many atoms are found in 5.20 g of magnesium (Mg)?

Explanation:

In order to go from mass of magnesium to atoms of magnesium, we have to do two things:

   Convert mass of Mg to moles of Mg using the molar mass of Mg as a conversion factor

   Convert moles of Mg to atoms of Mg using Avogadro's number (6.02×1023) as a conversion factor

Step 1:

Before we start, I should note that the molar mass of Mg is 24.31gmol. We can go from mass to moles using dimensional analysis. The key to dimensional analysis is understanding that the units that you don't need any more cancel out, leaving the units that are desired:

48.60g

×1mol24.31g

=2.00mol

Step 2:

We'll use this relationship:

www.sprinklernewz.uswww.sprinklernewz.us

Using the moles of Mg that we just obtained, we can use Avogrado's number to perform dimensional analysis in order to cancel out units of mol to end up with atoms of Mg:

2.00mol

×6.02×1023atoms1mol

=1.204×1024atoms

Thus, 48.60g of Mg is equivalent to 1.204×1024atoms

Hope this helped :)