Use the unbalanced equation to answer the question.
C4 H10 + O2 → CO2 + H2O
How many molecules of O2 are needed to balance the equation?
a 7
b 12
c 13
d 26
To balance the equation, we need to have the same number of atoms of each element on both sides of the equation.
Looking at the unbalanced equation, we see that there are 2 atoms of oxygen on the left side (in the O2 molecule) and only 1 atom of oxygen on the right side (in the CO2 molecule).
To balance the oxygen atoms, we need to have twice as many O2 molecules on the left side. Therefore, the balanced equation is:
C4 H10 + 13/2 O2 → 4 CO2 + 5 H2O
So we need 13/2 O2 molecules to balance the equation.
The answer is therefore c) 13.