ahhh help in equations?

Question

i don't understand what i put after the yeild sign in this equation.

Al(s) + Fe2O3(s)

info: Elemental irn is produced in what is called a thermite reaction because it produces enough heat that the iron is intially in the molten state. the liqiud iron can then be used to weld bars together.

question: What mass of Al is needed to produce 750g of Fe? How many formula units of FeO3 are used in this process( i don't get this second part to the question)

please help.

Answer 1

The full reaction is

2Al + Fe2O3 == Al2O3 + 2Fe
The stoichiometry works as follows:

Divide 750 g of Fe by its molecular mass. Multiply the moles of Fe by the molar ratio of 2Fe/2Al and you have the moles of Al (its the same). Now multiply by molar mass of Al and you are done.

For your second part, it seems that the question is how many moles of Fe2O3 are involved. Based on the balanced equation above, it is half as many moles as Fe or Al.

Answer 2

2 Al + Fe2O3 ----> Al2O3 + 2 Fe

If elemental iron is being produced, then the reaction is an oxidation-reduction reaction, where aluminum is oxidized and iron is reduced.

As for the second part, for every 2 moles of iron, you need 2 moles of aluminum. To get 750 grams of iron, which is 13.4 moles, you will need 13.4 moles of aluminum, or 362 grams. As for formula units, I'm assuming they mean molecules of Fe2O3, which you would use 6.7 moles or 4.03 * 10^24 molecules.