The oxidation number of Cl in HClO₄ is?

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  • 1 year ago

    The oxidation state of chlorine in perchloric acid is +7.

    Please don't assume that chlorine has a charge of +7.  It's not an "ionic" substance, and even if it was it couldn't possibly have a charge that large.  The oxidation state of an element is an assigned number, only coincidentally may it agree with an actual charge, usually when the ion is in solution.

    We can assign the oxidation state of chlorine because there is agreement on the assigned oxidation states of hydrogen (+1) and oxygen (-2).  The sum of the oxidation states for a compound must equal zero.

    +1x -2 -2 -2 -2

    H Cl O O O O 

    +1 +x 4(-2) = 0

    x = +7

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