Calculate the number of atoms in a 6.57×103 g sample of calcium.

Answer 1

Answer 2

Hi Tevo!

In order to solve out this problem, we need to find the molar mass of calcium and Avogadro's number.

The molar mass of calcium can be found on a periodic table, and will be given in g/mol (grams per mole) underneath the element's abbreviated symbol. For calcium, this is Ca and the molar mass is 40.078 g/mol (see: https://ptable.com/?lang=en#Properties)

Avogadro's number is a conversion factor that relates the # of atoms in one mole of substance. This number is 6.022 x 10²³ atoms per 1 mole.

Now that we've found everything we need, we can solve out the problem! :)

6.57 x 10³ g calcium/1 * 1 mol calcium/40.078 g calcium = 163.9303358 mol calcium

163.9303358 mol calcium * 6.022 x 10²³ atoms calcium/ 1 mol calcium = 9.87188482 x 10²⁵ atoms calcium

Since we're given 3 significant figures (or sig figs) in the problem from 6.57 x 10³, we do the same for our answer:

9.87 x 10²⁵ atoms calcium in the sample

Hope this helps!