Question

In a proper equation, which are the only numbers that can be altered ?

Answer 1

Answer:

because changing subscripts would mean you are changing the basic composition of the substance.

Explanation:

Let’s say that you are asked to balance the equation

H₂ + Cl₂ → HCl

You would immediately put a 2 in front of the HCl and write

H₂ + Cl₂ → 2HCl

But why can’t you write

H₂ + Cl₂ → H₂Cl₂?

This is also a balanced equation. However, we use the formulas in equations to represent elements and compounds. If we put a number (a coefficient) in front of the formula, we are simply using a different amount of the same substance. If we change the subscript in the formula, we are changing the substance itself.

Thus, HCl represents a molecule that contains one H atom attached to one Cl atom. H₂Cl₂ would represent a molecule in which two H atoms and two Cl atoms are somehow bonded together to give a new particle containing four atoms. Since the original equation listed HCl as the product, we are not answering the question that was asked.

BOTTOM LINE

When balancing equations, we can change only the coefficients in front of the formulas. We are not allowed to change the subscripts in the formulas.