Which law is the basis for the balancing of chemical equations?

Law of conservation of mass 

The correct answer is option 1. Law of conservation of mass.

The Law of Conservation of Mass, formulated by Antoine Lavoisier in the late 18th century, states that in a closed system, the total mass remains constant over time, regardless of the changes that occur within the system. In the context of chemical reactions, this law asserts that the total mass of the reactants must equal the total mass of the products.

When a chemical reaction occurs, atoms are rearranged to form new substances, but the total number of atoms of each element remains the same before and after the reaction. This means that no atoms are created or destroyed during the reaction.

Balancing a chemical equation involves ensuring that the number of atoms of each element is the same on both sides of the equation. This is achieved by adjusting the coefficients (the numbers written in front of chemical formulas) to ensure that the same number of atoms of each element is present on both the reactant and product sides.

For example, consider the reaction:

\[ \text{H}_2 + \text{O}_2 \rightarrow \text{H}_2\text{O} \]

In this equation, there are two hydrogen atoms and two oxygen atoms on the left side (reactants) and two hydrogen atoms and one oxygen atom on the right side (products). To balance the equation, we can adjust the coefficients:

\[ 2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O} \]

Now, there are four hydrogen atoms and two oxygen atoms on both sides of the equation, satisfying the Law of Conservation of Mass.

Overall, the Law of Conservation of Mass serves as the fundamental principle behind balancing chemical equations, ensuring that the total mass remains constant before and after a chemical reaction.