Question

A doctor prescribed magnesium oxide as a health supplement. Assuming that a capsule contains 400mg magnesium oxide, determine the number of unit cells of magnesium.

Answer 1

No of moles of megnesium = weight/M.wt

                                      =[ 400x10^-3]/[24]

                                      =1/60

                                       =0.01667 moles

No of Megnesium units = 6.023x10²³ xNo of moles

      1 unitcell                =   4 formula units     [ since megnesium adapts F.C.C structure]

No of Megnesium units = 6.023x10²³ x0.01667

      1 unitcell                =   4 formula units    

          X                    =    6.023x10²³ x0.01667

             X=[0.1004x10²³]/4

                 X=0.02510x10²³

The number of unit cells of magnesium is 0.02510x10²³