An unbalanced chemical equation is shown:

H2O2 → 2H2O + O2

Which of the following statements explains why the equation is not balanced?

Two H2O2 molecules should decompose to form the given products.
Four H2O2 molecules should decompose to form the given products.
Two H2O2 molecules should undergo a synthesis reaction to form the given products.
Four H2O2 molecules should undergo a synthesis reaction to form the given products.

1 answer

The correct statement that explains why the equation \( \text{H}_2\text{O}_2 \rightarrow 2\text{H}_2\text{O} + \text{O}_2 \) is not balanced is:

Two H2O2 molecules should decompose to form the given products.

Here's why:

Looking at the unbalanced equation:

  • On the left side (reactants), there is 1 molecule of \( \text{H}_2\text{O}_2 \).
  • On the right side (products), there are 2 molecules of \( \text{H}_2\text{O} \) and 1 molecule of \( \text{O}_2 \).

Now let's count the number of each type of atom:

  • Hydrogen (H):

    • Reactants: 2 (from \( \text{H}_2\text{O}_2 \))
    • Products: 4 (2 from each of the 2 water molecules)
  • Oxygen (O):

    • Reactants: 2 (from \( \text{H}_2\text{O}_2 \))
    • Products: 3 (2 from the two water molecules and 1 from the oxygen gas)

Since there are 4 hydrogen atoms and 3 oxygen atoms in the products, while we started with only 2 hydrogen and 2 oxygen atoms from 1 \( \text{H}_2\text{O}_2 \), the equation is not balanced. To balance it correctly, you would indeed require 2 molecules of \( \text{H}_2\text{O}_2 \) to properly yield the products.