Answer to Question #264575 in General Chemistry for nam

Question

A thermite reaction is necessary to produce molten iron. This reaction involves

Fe 3 O 4 and Al and is described by:

8 Al + 3 Fe 3 O 4 → 9 Fe + 4 Al 2 O 3

If 198.5 g Al and 365.5 g Fe 3 O 4 are used, what mass of the excess reagent

remains unused at the end of the reaction?

Answer 1

The units will always be in g. What mass of iron will be made when 16g of Fe2O3 reacts in the thermite reaction Fe2O3 + 2Al → 2Fe + Al2O3? The number of moles of iron oxide reacting is given by 16 / 160 = 0.1. The balanced equation tells you that there will be 0.2 moles of Fe made, so the mass is 0.2 x 56 = 11.2 g.