C3H8 +________O2 ---------3CO+4H2O . Which is the balance the reaction

Question

A. 1
B. 7
C. 5
D.3

Answer 1

If you had to balance this equation as it is, then the coefficient of O2 would be (7/2), since there are seven O atoms on the right.

However, the correct equation of the combustion of propane (C3H8) is:
C3H8 + _____O2 ---------> 3CO2 + 4H2O
(That is, CO2 in place of CO)

In this case, there are ten O atoms on the right side, and hence 5 molecules of O2 are required.

So, the answer is (C)