This is for my chemistry course

Question

Balance the equation below and answer the question:

Fe + O₂ = Fe₂O₃

How many grams of Fe₂O₃ are produced when 100,000 molecules of O₂ are reacted?

Answer 1

the balanced equation is: 4Fe + 3O2 --------> 2Fe2O3

The # of grams of Fe2O3 is determined in this fashion.

Step 1: Convert 1.0 x 10^5 molecules of O2 to moles of O2

Using Avogadros number and relationship that 1 mole of any representative particle (in this case molecules)

is equal to 6.02 x 10^23 molecules.

1.0 x 10^5 molecules O2 x 1 mol O2/6.02 x 10^23 molecules O2 = 1.66 x 10^-19 mol O2

Step 2: using the molar ratio of 3 moles O2 to 2 moles Fe2O3 in the balanced formula calculate the # of moles of Fe2O3 produced assuming O2 is the limiting reactant.

1.66 x 10^-19 mol O2 x 2 mol Fe2O3/3 mol O2 = 1.11 x 10^-19 mol Fe2O3

Step 3: to convert the moles of Fe2O3 to grams you first need to calculate the molar mass of

Fe2O3 = 159.7 g

Step 4: then using the relationship that 1 mole of any element or compound equals its molar mass:

1.11 x 10^-19 mol Fe2O3 x 159.7 g Fe2O3/1 mol Fe2O3 = 1.77 x 10^-17 g Fe2O3.