If 31.5 of molten iron(III) oxide reacts with 175 of aluminum, what is the mass of iron produced?

Answer 1

Write and balance the equation.
Convert 175 g Al to moles. moles - grams/molar mass
Convert 31.5 g iron(III) oxide to oles.

Using the coefficients in the balanced equation, convert moles Al to moles iron.
Do the same for ferric oxide.
You will obtain two answers; of course only one can be correct. The correct answer in limiting reagent problems is ALWAYS the smaller one and the reagent producing that number is the limiting reagent. The convert the smaller value to grams. g = moles x molar mass.