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In 2H2O2(aq) giving 2H2O(l) and O2(g), one element is both oxidized and reduced. What is this type of reaction called?
AA neutralization reaction
BA precipitation reaction
CA disproportionation reaction
DA single-displacement reaction
Answer & Solution
Correct answer: C. A disproportionation reaction
1. Hydrogen peroxide is a peroxide, so oxygen in H2O2 has oxidation number -1.
2. In the O2 product oxygen is an elemental substance, so its value is 0.
3. Going from -1 to 0 is an increase, so some oxygen is oxidized.
4. In the H2O product oxygen has its usual value of -2.
5. Going from -1 to -2 is a decrease, so some oxygen is also reduced.
6. One element undergoing both changes is a disproportionation reaction.
7. In such a reaction the same substance acts as both the oxidant and the reductant.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.2 Classifying Chemical Reactions_
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