Question

How many atoms of 12C are in a 3.50 g sample of this particular isotope?

Answer 1

Atomic mass C = 12 u.m.a

12 g ------------------ 6.02x10²³ atoms
3.50 g -------------- ??

3.50 x ( 6.02x10²³) / 12 =

2.107x10²⁴ / 12 => 1.755x10²³ atoms

hope this helps!