5. A vitamin contains 1.5 x 10' grams of zinc. How many moles of zinc are in the vitamin?

                      2.29 × 10⁻⁴ moles

Explanation:

Data Given:

                 Chemical Symbol of Zinc  =  Zn

                 Mass of Zinc   =  1.5 × 10⁻² g

                 A.Mass of Zinc  =  65.38 g.mol⁻¹

The Atomic Mass of Zinc can be obtained from periodic table. While, the mass is given in statement. Also, it is important to know the symbol because some elements exist in diatomic or polyatomic forms i.e. H₂, N₂, S₈ e.t.c.

                 Mole is the unit used to calculate the amount of substance. It has following general forms,

                                             Mole =  Mass / M.Mass

And,

                     Mole =  # of Particles / 6.022 × 10²³ particles.mol⁻¹

Hence, using first equation,

                     Moles  =  1.5 × 10⁻² g / 65.38 g.mol⁻¹

                     Moles =  2.29 × 10⁻⁴ moles

i think it's letter a.