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Which rule governs the oxidation number of hydrogen in compounds?
AIt is minus one with nonmetals and plus one with metals
BIt is plus one with nonmetals and minus one with metals
CIt is plus one in every compound without exception
DIt is minus one in every compound without exception
Answer & Solution
Correct answer: B. It is plus one with nonmetals and minus one with metals
1. Hydrogen bonded to a nonmetal, as in H2S or HCl, is assigned +1.
2. Hydrogen bonded to a metal, as in AlH3 or NaH, is assigned -1.
3. So the sign depends on the partner element.
4. Assuming +1 everywhere would give a wrong answer for a metal hydride.
5. In elemental H2 the value is zero, since that is an elemental substance.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.2 Classifying Chemical Reactions_
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