How many grams of Al are needed to react with 91.8 grams of FeO
3FeO + 2Al —> 3 Fe +Al2O3

Ans : 22.86 gm of Aluminium

Solution,

                        3FeO + 2Al ---> 3 Fe +

Given                   3          2                    

Find                    1.27       x

By the given gms of FeO find its mole and put the moles in the find,

                  Given mass of FeO is 91.8

                   Molecular mass of FeO is 71.8

                                         n =  

                                         n = 1.27 moles of FeO  

Now solve for x,

                             x = 0.85 moles

These are just moles of Aluminium that we need to react with FeO, so to find Grams of Aluminium we need,

                                Mass = moles x molecular mass

                                Mass = 0.85 x 27(atomic mass of Al)

                                Mass = 22.86 grams of aluminium is what we need

it means there are 3 atoms of oxygen