A compound containing 3 atoms of carbon and 8 atoms of hydrogen is combined in a reaction with oxygen molecules. The two end products of this equation are carbon dioxide and water. What element should you look at first in balancing this equation?
A. oxygen
B. Hydrogen
C. Carbon
D. Dioxide
I have answered problems like this several times. There are many many different ways to balance equations and each person has a method that s/he prefers. So there is no one way of doing it. Personally, I think this is a VERY poor question but you don't need to tell your instructor that. I would start with carbon but there is no reason not to start with hydrogen. There are some good reasons not to start with oxygen.
The element that you should look at first in balancing this equation is C. Carbon.
To balance this equation, you should first look at the element that appears in only one compound on each side. In this case, both carbon dioxide (CO2) and water (H2O) contain oxygen atoms, so they are not exclusive to one compound. However, carbon appears in carbon dioxide, while hydrogen appears in both the compound containing only hydrogen (H2) and water (H2O).
Therefore, the element you should look at first in balancing this equation is carbon (C).