Here's why:
* Coefficients represent the number of moles of each reactant and product. Changing the coefficient changes the amount of each substance involved in the reaction.
* Subscripts in chemical formulas indicate the number of atoms of each element within a molecule. You cannot change subscripts to balance an equation, as that would change the identity of the molecule itself.
Example:
Unbalanced equation: H₂ + O₂ → H₂O
Balanced equation: 2H₂ + O₂ → 2H₂O
In this example, we added a coefficient of "2" in front of both H₂ and H₂O. This ensures that we have the same number of hydrogen and oxygen atoms on both sides of the equation (4 hydrogen atoms and 2 oxygen atoms).
Key Principle:
The law of conservation of mass dictates that in a chemical reaction, the total mass of the reactants must equal the total mass of the products. Balancing equations ensures that the number of atoms of each element remains the same on both sides, thus satisfying the law of conservation of mass.
