chem
posted by greeny .
over the years, the thermite reaction has been used for welding railorad rails, in incendiary bombs, and to ignite solid fuel rocket motors. The reaction:
Fe2O3(s) + 2 Al (s) > 2 Fe(l) + Al2O3 (s)
What masses of iron ( III) oxide and aluminum must be used to produce 15.0 grams of iron? What is the maximum mass of aluminum oxide that could be produced?

15g of Fe is 15/55.845 = 0.2686 moles
Each mole of Fe requires 1 mole of Fe2O3 and 2 moles of Al.
mol wt Fe2O3 = 2*55.845+3*15.999 = 159.687
mol wt Al = 26.982
so, we need
.2686*159.687 = 42.9g Fe2O3
.2686*2*26.982 = 14.5g Al
mol wt Al2O3 = 2*26.982+3*15.999 = 101.961
so, we get .2686*101.961 = 68.9g Al2O3 
We first check if the equation is balanced and according to our equation its already balanced.2nd we find the ratios from the equation.
FeO3+2AL=2Fe+AL2O3
2 = :2
x = :mass over
rmm=the answer you u will find when u do mol=mass/rmm.
Then n=mass/molar mass
Mass=mol x rmm
mass=0.134 x 159.6
21.359.final