In a chemical reaction, what is meant by the term product in contrast to reactant?

Introduction / Context:
Understanding the basic language of chemical equations is essential for studying chemistry. Every reaction is described using reactants and products. Reactants are the starting substances, while products are the new substances formed. This question directly asks for the definition of a product in the context of a chemical reaction, which is a core concept in school level chemistry.

Given Data / Assumptions:

• Chemical reactions are written in the form: Reactants → Products.
• Reactants are present at the beginning of the reaction.
• Products are present at the end of the reaction.
• The options present different possible descriptions of a product, some of which actually describe reactants or catalysts.

Concept / Approach:
A product is defined as a substance that is generated when reactants undergo a chemical change. This may involve breaking bonds, forming new bonds, and rearranging atoms. Products usually have different properties from the reactants. In a chemical equation, products are written on the right hand side of the arrow. Catalysts and solvents may participate in the process but are not normally called products unless they are chemically changed and appear on the right side of the equation as new substances.

Step-by-Step Solution:
Step 1: Recall the layout of a chemical equation. Reactants are written on the left side, products on the right side of the arrow. Step 2: Define reactant. A reactant is a substance present at the start that takes part in the reaction and may be consumed. Step 3: Define product. A product is a substance that is formed as a result of the reaction and appears at the end. Step 4: Compare with the given options to identify the one matching this definition.

Verification / Alternative check:
Consider the reaction: 2H2 + O2 → 2H2O. Hydrogen and oxygen gases are present at the start and are reactants. Water is not present initially but appears after the reaction as a new substance with different properties; therefore water is the product. In an acid base neutralisation reaction such as HCl + NaOH → NaCl + H2O, the salt and water are products. In each case, products are clearly the substances formed by chemical change, confirming the definition used in the correct option.

Why Other Options Are Wrong:
Option B: This describes a reactant, not a product, because it is present at the start and is consumed. Option C: A catalyst speeds up a reaction without being consumed and is not usually called a product unless it is chemically changed. Option D: A solvent dissolves reactants and may remain unchanged, but it is not normally classified as a product in the reaction equation.

Common Pitfalls:
Students sometimes confuse reactants and products because both appear in the equation. Another common error is to think that anything present in the reaction mixture at the end is a product, including unchanged catalysts or solvents. Remember that products are new substances created by the reaction, while reactants are the starting substances that undergo change. Looking at which side of the arrow a substance appears on in a balanced equation helps avoid confusion.

Final Answer:
In a chemical reaction, a product is a substance that is formed as a result of the chemical reaction.