What does the term reactants refer to in a chemical equation?

• A. Substances on the left
• B. Substances on the right
• C. Substances that catalyze the reaction
• D. Substances that dissolve

Answer: (A)

Reactants are the starting materials in a chemical reaction. In a chemical equation, they sit on the left side of the arrow and are the substances that participate in the reaction and are transformed into products. The arrow points toward the right, showing the direction from reactants to products. For example, in the reaction that forms water, the reactants are hydrogen gas and oxygen gas, and the product is water. Coefficients tell you how many molecules of each reactant participate. Catalysts may speed up a reaction but are not consumed and are not considered reactants. Substances that dissolve refer to solvents or solutes, not the reactive starting materials in that equation.