The oxidation number of oxygen in hydrogen peroxide, H2O2, is
Correct answer: C. minus 1
- A. minus 2
- B. zero
- C. minus 1
- D. plus 2
Explanation
Hydrogen is plus 1, so the two oxygens must total minus 2 between them, giving minus 1 each, which is the exception to the usual rule of minus 2 for oxygen. This intermediate value is why hydrogen peroxide can act both as an oxidising agent, going to minus 2, and as a reducing agent, going to zero. In compounds with fluorine, oxygen takes a positive oxidation number.
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About Oxidation and Reduction
Oxidation involves loss of electrons, increase in oxidation number or addition of oxygen, while reduction involves electron gain, decrease in oxidation number or removal of oxygen. The topic covers oxidising and reducing agents, oxidation-number changes, redox equations and the distinction between oxidation at the anode and reduction at the cathode.
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