How many moles are equal to 1.2 x 10^21 molecules of lithium?

a) 7.2 x 10^44 moles

b) .2.0 moles

c) 7.2 x 10^24 moles

d) 2.0 x 10^-3 moles

1 mole 6.02 x 10²³ molecules
( moles lithium ) 1.2 x 10²¹ molecules

( moles lithium ) = (1.2 x 10²¹ ) x 1  / ( 6.02 x 10²³ )

= 1.2 x 10²¹ / 6.02 x 10²³

= 2.0 x 10⁻³ moles of lithium

Answer D

hope this helps!