Question

Oxidation state of oxygen in \(\text{H}_2\text{O}_2\)

Hint:

Memorize the exceptions for Oxygen's oxidation state:
- Standard oxides (\(\text{H}_2\text{O}, \text{CO}_2\)): -2
- Peroxides (\(\text{H}_2\text{O}_2, \text{Na}_2\text{O}_2\)): -1
- Superoxides (\(\text{KO}_2\)): -1/2
- With Fluorine (\(\text{OF}_2\)): +2

Answer 1

Step 1: Understanding the Concept:
The oxidation state is the hypothetical charge an atom would have if all its bonds to different atoms were fully ionic. While oxygen typically has an oxidation state of -2, peroxides are a key exception due to the presence of an oxygen-oxygen single bond (\(O-O\)).
Step 2: Key Formula or Approach:
The fundamental rule for finding oxidation numbers is that the algebraic sum of the oxidation states of all atoms in a neutral molecule must equal zero. Let the oxidation state of the unknown atom be \(x\).
Step 3: Detailed Explanation:
The given compound is hydrogen peroxide, \(\text{H}_2\text{O}_2\).
The generally accepted rules for assigning oxidation numbers state that:
- The oxidation state of Hydrogen (H) when bonded to non-metals is +1.
Let the oxidation state of Oxygen (O) in this compound be \(x\).
Applying the sum rule for the neutral molecule \(\text{H}_2\text{O}_2\):
\[ 2 \times (\text{Oxidation state of H}) + 2 \times (\text{Oxidation state of O}) = 0 \]
\[ 2 \times (+1) + 2x = 0 \]
\[ +2 + 2x = 0 \]
\[ 2x = -2 \]
\[ x = -1 \]
Therefore, each oxygen atom in \(\text{H}_2\text{O}_2\) has an oxidation state of -1. This is characteristic of the peroxide ion (\(\text{O}_2^{2-}\)).
Step 4: Final Answer:
The oxidation state of oxygen in \(\text{H}_2\text{O}_2\) is -1.