How do I balance this

Question

Write a balanced chemical equation based on the following description: butanoic acid, C₃H₇COOH(l) burns in air

Answer 1

This is a combustion reaction and requires oxygen (O₂) and the products will be carbon dioxide (CO₂) and water (H₂O). This is something you just have to learn/know/memorize. So, we have...

C₃H₇COOH(l) + O₂ ==> CO₂ + H₂O

First, we balance the C's and since all the C ends up in CO2, we have the following:

C₃H₇COOH(l) + O₂ ==> 4CO₂ + H₂O ... This balances the C atoms (4 on each side)

Next, we balance the H's and all the H ends up in H2O, so we have the following:

C₃H₇COOH(l) + O₂ ==> 4CO₂ + 4H₂O ... This balances the H atoms (8 on each side)

Finally, we balance the O atoms by adjusting the number in front of the O₂ as follows:

C₃H₇COOH(l) + 5O₂ ==> 4CO₂ + 4H₂O ... balanced for C, H, and O