Find the oxidation number of `Cl` in `HCl, HClO,ClO_(4)^(ө)`, and `Ca(Ocl)Cl`.

Answer

A, C, D

Explanation

It is obvious that in `HCl` the oxidation number for `H` is `+1` and therefore, for `Cl` it should be `-1`.
In `HClO`, the oxidation number for `H` is `+1` and for `O` is `-2` and therefore, for `Cl` it should be `-1`.
In `ClO_(4)^(ө)`, the oxidation number for `O` is `-2` and therefore, for `Cl` it should be `+7`.
In `Ca(OCl)Cl`., the oxidation number of `Ca` is `+2` and that of `O` is `-2`
`1xx2+1xx(-2)-2("oxidation number" of Cl)=0`
or oxidation number of `Cl` is `0`.
It may be mentioned here that one `Cl` atoms exists as chloride ion for which the oxidation number is `-1` and the other `Cl` atom exists as chlorite ion in which the oxidation number of `Cl` is `+1`. The oxidation number of `Cl` in the compound is the average of the oxidation numbers of all atoms of the element. In this case, average is zero in agreement with our calculated value.