Question

you are given a sample containing 0.70 moles of a substance how many atoms are in the sample if the substance is platinum ?

Answer 1

1 mole ------------- 6.02 x 10²³ atoms
0.70 moles -------- ( atoms platinum )

atoms platinum = 0.70 x ( 6.02 x 10²³ )  / 1

 = 4.2 x 10²³ atoms platinum

hope this helps!