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!
