atoms to grams of calcium

Question

How many atoms of calcium are in 3456 grams of calcium?

a) 5.19e25

b) 2.30e-19

c) 8.34e28

d) 1.43e-22

Answer 1

Avogadro's number = 6.02x10²³ particles per mol (particles can be atoms, molecules, formula units, etc)

atomic mass Ca = 40.08 g / mol

moles Ca = 3456 g x 1 mol / 40.08 g = 86.228 moles

atoms of Ca = 82.228 moles x 6.02x10²³ atoms / mol = 519.1x10²³ atoms = 5.191x10²⁵ atoms of Ca

ANSWER (a)