Question

what coefficient is placed in front of o2 to complete the balancing of the following equation? c5h8 (l)+? o2 (g) → 5 co2 (g) + 4 h2o (g)
a d) 7
b a) 1
c c) 5
d b) 3

Explanation:

Step1: Count oxygen atoms on product - side

In $5CO_2$, the number of oxygen atoms is $5\times2 = 10$. In $4H_2O$, the number of oxygen atoms is $4\times1=4$. So the total number of oxygen atoms on the product - side is $10 + 4=14$.

Step2: Determine coefficient of $O_2$

Let the coefficient of $O_2$ be $x$. Each $O_2$ molecule has 2 oxygen atoms. So $2x$ oxygen atoms come from $O_2$. We set $2x = 14$, then $x = 7$.

Answer:

A. D) 7