Given the following reaction, answer the question under it: 2 Fe2O3
Fe +302
If the mass of Fe2O3 is 40 grams, what is the mass of the products (Fe
and O2)
O 40 g
120 g
O 80 g
O
20 g

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.