How many potassium atoms would there be in133 mg of potassium

Answer 1

1 mol K = 39.098 g

133 mg K = 0.133 g

moles K in 133 mg = 0.133 g K x 1 mol K / 39.098 g = 0.003402 moles = 3.402x10^-3 moles K

There are Avogadro's number of atoms in 1 mol, thus...

3.402x10^-3 moles x 6.02x10²³ atoms /mole = 2.04x10²¹ K atoms in 133 mg of K