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 both contain four elements - Al, Zn (or Cu), S, and O. The process will go smoothest if you begin by balancing the element Al. Once balanced, proceed with the elements S and O; balancing one of these will automatically balance the other. Finally, balance the Zn (or Cu). Even though it is not required for the question, it would be wise to do an atom count to insure that the number of atoms of each element are the same on the reactant and the product side.