Oxidation number question

[sticky1]

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I am confused by a question in TPR which asks for the oxidation number of hydrogen. How do you determine the oxidation number of hydrogen in Ca5(H2PO4)2?

 

[Temperature101]

I am confused by a question in TPR which asks for the oxidation number of hydrogen. How do you determine the oxidation number of hydrogen in Ca5(H2PO4)2?

What is the answer?

 

[Sterling Archer]

I am confused by a question in TPR which asks for the oxidation number of hydrogen. How do you determine the oxidation number of hydrogen in Ca5(H2PO4)2?

As a general rule: Hydrogen has a -1 oxidation state when attached to elements less electronegative than itself (ex. LiH, NaH); hydrogen has a +1 oxidation state when attached to elements more electronegative than itself (ex. H2O, HCl)

 

[Greedo]

As a general rule: Hydrogen has a -1 oxidation state when attached to elements less electronegative than itself (ex. LiH, NaH); hydrogen has a +1 oxidation state when attached to elements more electronegative than itself (ex. H2O, HCl)

That rule is confusing though because the oxidation state of hydrogen in both BH3 and NH3 is -1, and N is more electronegative than H but B is less electronegative than H. Can you explain that? I just missed two EK 1001 questions (#866 and #900) because of this!

 

[Greedo]

That rule is confusing though because the oxidation state of hydrogen in both BH3 and NH3 is -1, and N is more electronegative than H but B is less electronegative than H. Can you explain that? I just missed two EK 1001 questions (#866 and #900) because of this!

Just realized I misspoke, the oxidation number of hydrogen in NH3 is +1 and the oxidation number of hydrogen in BH3 is -1. Makes sense now!