Question

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

Answer 1

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