How many grams Al and how many grams Cr2O3 should be taken to gain 10g Cr.How many grams of Al2O3 will be spent?
Reaction: Cr2O3 + 2Al -> 2Cr + Al2O3
mols Cr = grams/atomic mass.
Using the coefficients in the balanced equation, convert mols Cr to mols Al
Do the same to determine mols Cr2O3.
Now convert mols Al and mols Cr2O3 to grams by g = mols x molar mass.