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Q90 (NDA-II/2017) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Basic chemical principles Answer Verified

Consider the following reaction ; CH4 + 2O2 -> CO2 + 2H2O Which of the following about the reaction given above is/are correct ? 1. Carbon is oxidized. 2. Hydrogen is oxidized. 3. Hydrogen is reduced. 4. Carbon is reduced. Select the correct answer using the code given below :

Result
Your answer: —  ·  Correct: A

Explanation

In the combustion of methane (CH4 + 2O2 → CO2 + 2H2O), carbon undergoes oxidation while oxygen undergoes reduction. In methane (CH4), carbon has an oxidation state of -4, which increases to +4 in carbon dioxide (CO2), signifying a loss of electrons and thus oxidation [1]. Conversely, elemental oxygen (O2) has an oxidation state of 0 and is reduced to -2 in both CO2 and H2O. Regarding hydrogen, its oxidation state remains +1 in both CH4 and H2O, meaning it is neither oxidized nor reduced in this specific redox process. While some simplified definitions suggest hydrogen is oxidized because it 'gains oxygen', formal oxidation state rules confirm that only carbon's oxidation state changes among the reactants containing carbon and hydrogen. Therefore, only statement 1 is technically correct.

Sources

  1. [1] https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:chemical-reactions/x2eef969c74e0d802:oxidation-reduction-redox-reactions/a/oxidation-number
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