How many moles are in 7.777x 1024 molecules of Mg2. Watch your significant figures 12.91 moles Mg2

12.9 moles Mg2

12 atoms Mg2

12.9 atoms Mg2

number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.

where are the choice options?