How many atoms are in 137 g of calcium?

2.047x 10²⁴  atoms

Explanation:

To calculate the n° of moles of Ca that they are in 137 g, we can use the next relation:

n = mass/atomic mass = (137 g)/(40.078 g/mol) = 3.4 mol.

For each mole of a molecule contains Avogadro's number of molecules (NA = 6.022 x 10²³).

Using cross multiplication:

1 mole of Ca contains → 6.022 x 10²³ atoms.

3.4 moles of Ca contains → ??? atoms.

∴ 3.4 mole of (137 g) Ca contain = (3.4 mol)(6.022 x 10²³) = 2.047x 10²⁴  atoms.