A balanced chemical equation shows the number of particles of each substance involved in a chemical reaction. Such an equation includes formulas and coefficients. The formulas include symbols for each type of atom in the substance. The coefficients are the numbers present in front of the formulas. The act of balancing a chemical equation involves selecting the lowest possible set of coefficients that would provide the same number of atoms of each element on the reactant and the product side of the equation.
 

To be successful with this question, you need to know what a balanced chemical equation involves. You also need to have a good strategy for how to balance a chemical equation. Finally, you will need to make sure you know how to conduct an Atom Count. The two infographics below describe these three ideas. Study the graphics, giving particular attention to the Know How to Count Atoms, the Step-by-Step Balancing Method, and the Example sections in the second infographic. Some specific information regarding this question are provided after the second infographic.

 

Some Specifics About This Question Group

The two versions of questions in this Question Group are similar. They each involve combustion reactions. A hydrocarbon is reacted with oxygen; the products are CO₂and H₂O. There are three elements that must be balanced - C, H, and O. Since the element O shows up in two formulae on the product side, it would be best to start by balancing either C or H first. Balance one of these elements; then balance the other element.  Once the elements C and H have been balanced, direct your attention to the balancing of O. This can be done by inserting a coeffiient in front of O₂ on the reactant side.  As you proceed with this method, you will notice that a half-number coefficient is required for O₂. But coefficients must be whole numbers. So the problem can be resolved by multiplying every coefficient by 2. Once done, conduct an atom count to insure accuracy and completion.