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When assigning oxidation numbers, do you include the coefficients and subscripts?
example:
half-rxn:
2H+ (aq) ---> H2 (g)
does Hydrogen s ox. no. go from 2+ to 0 or from 1+ to 0?
2 Answers
- davidLv 75 years agoFavorite Answer
ANY element is considered in the free state, 0 oxidation number, if it is not combined with other elements .. H2 is 0 ox. number --- S8 is still 0 ox number ... and single atoms Cu, etc are 0 ox. number.
When combined with other elements in a compound then the ox. number will depend on the subscripts and your knowledge of electron configurations and stability via the octet rule.
--- So H2O the H has a +1 ox number and the O has a -2 ox number so the sum of all ox. numbers in the compound = 0 ..
(1+)X2 + (-2) = 0 <<< here you will use the subscripts.
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in your example of a half-reaction
2H+ (aq) ---> H2 (g)
EACH H has a +1 ox. number on the left, meaning each H must gain 1 e- ... since there are 2H+ then you need 2 e-
2H+ (aq) + 2e- ---> H2 (g)
