Answer:
2.047x 10²⁴ atoms
Step-by-step 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.