Given the equation: 4Al2O3 + 9Fe --> 3Fe3O4 + 8Al

If 27.5 g of Al2O3 reacted with 8.4 g of Fe, how many of Fe 3O4 are formed?

a) Calculate the limiting reactant

b) Calculate the number of grams of Al produced.

c) Calculate the number of grams of Fe3O4 produced.

d) Calculate the percent yield if 10g of Fe O4 were obtained?

a)   is the limiting reagent

b) 3.59 g

c) 11.6g

Explanation:

To calculate the moles :

According to stoichiometry :

a) 9 moles of  require= 4 moles of

Thus 0.15 moles of will require=  of

Thus is the limiting reagent as it limits the formation of product and is the excess reagent.

b) As 9 moles of give = 8 moles of

Thus 0.15 moles of give =  of

Mass of

c) As 9 moles of give = 3 moles of

Thus 0.15 moles of give =  of

Mass of

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.