Question #f86bf

1 Answer
anor277
Jan 10, 2016

The carbide ion, #(C-=C)^-2#, has a formal charge of #-2#. The oxidation number of each #C# is #-I#.

Explanation:

The sum of the oxidation numbers must add to the charge of the ion. Since the #C#'s have a #-I# oxidation state, and the charge of acetylide is #-2#, this condition is satisfied. Of course, #Ca# is an alkaline earth metal, and has an oxidation number of #+II#.

To expand on the question, calcium carbide is clearly the derivative of acetylene gas, #H-C-=C-H#. Oxidation numbers may be assigned when we break the bonds, with the charge going to the most electronegative atoms (here #C#). Can you give the oxidation numbers of #C# for methane, ethane, and ethylene??

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