UPSC One
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2016 · Q27

Which one of the following statements is correct?

General KnowledgeChemistry
  1. AThe oxidation number for hydrogen is always zero.
  2. BThe oxidation number for hydrogen is always +1.
  3. CThe oxidation number for hydrogen is always -1.
  4. DHydrogen can have more than one oxidation number.

Explanation

Hydrogen exhibits an oxidation number of +1 in most compounds (e.g., H2O, HCl), −1 in metal hydrides (e.g., NaH), and 0 in elemental H2. Since it takes more than one value depending on the compound, the only correct statement is that hydrogen can have more than one oxidation number.