Using the equation, #Fe_2O_3 + 2Al -> 2Fe + Al_2O_3#, how many grams of #Al# are needed to completely react with 135 grams of #Fe_2O_3#?
The coefficients in the equation provide a molar ratio between the chemical species in the equation, so you must first convert the mass of iron (III) oxide to moles of iron (III) oxide by multiplying it by the inverse of its molar mass.
Then, by looking at the relationship between the moles of iron (III) oxide and aluminum, you can determine the number of moles of aluminum per mole of
Finally, convert the number of moles of aluminum to grams of aluminum by multiplying by its molar mass. After unit cancellation, you can determine that 45.6 g Al is necessary to completely react with 135 g