Question

How many molecules are in 69 grams of Na?

Answer 1

Molar mass Na = 23.0 g/mol

1 mol ---- 23.0 g
n mol ---- 69 g

n = 69 / 23.0

n = 3.0 moles

1 mole -------- 6.02x10²³ molecules
3.0 moles ---- ?

3.0 * 6.02x10²³ / 1

= 1.806x10²⁴ molecules

hope this helps!