Calculate the number of moles of carbon dioxide formed when 40.0 moles of oxygen is consumed in the burning of propane. Note the equation is unbalanced.

C3H8 + O2 - - - > CO2 + H2O:

A. 40.0 mol CO2

B. 42.0 mol CO2

C. 20.0 mol CO2

D. 24.0 mol CO2

The first step is to balance the equation:

C3H8 + 5O2 - - - > 3CO2 + 4H2O

Check the balance

element left side right side

C 3 3

H 8 4*2 = 8

O 5*2=10 3*2 + 4 = 10

Then you have the molar ratios:

3 mol C3H8 : 5 mol O2 : 3 mol CO2 : 4 mol H2O

Now you have 40 moles of O2 so you make the proportion:

40.0 mol O2 * [3 mol CO2 / 5 mol O2] = 24.0 mol CO2.

Answer: option D. 24.0 mol CO2