Answer: 193.8 grams
Explanation:

As can be seen from the chemical equation, 2 moles of aluminium react with 3 moles of oxygen.
Thus 3.40 moles of aluminium react with=
moles of oxygen.
But as the available amount of oxygen is less, oxygen is the limiting reagent as it limits the formation of product and aluminium is the excess reagent.
3 moles of oxygen react with 2 moles of aluminium
2.85 moles of oxygen react with=
moles of aluminium.
3 moles of oxygen give 2 moles of

2.85 moles of oxygen give=
moles of
.
Mas of
.