Answer:
1.50x10²⁴ atoms of Li are contained in 2.5 mol of it
Explanation:
NA (Avogadro's number) is the number of particles that occupy 1 mol, of anything. Let's do a rule of three:
1 mol of Li has 6.02x10²³ atoms
2.5 moles of Li have ( 2.5 .NA) /1 =1.50x10²⁴
