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Arrange HClO_(4), HClO_(3), HClO_(2), HClO in order of (i) decreasing acidic strength (ii) increasing oxidizing power. Give reasons. |
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Answer» Solution :(i) Acidic strength : `HClO_(4) gt HClO_(3) gt HClO_(2) gt HClO` Reason : All these acids on losing a proton give their corresponding conjugate bases, i.e., `ClO^(-), ClO_(2)^(-), ClO_(3)^(-) and ClO_(4)^(-)`. Their structures are :  Since oxygen is more electronegative than chlorine, therefore, the dispersal of the -ve CHARGE present on oxygen atom (singly BONDED to CI) INCREASES as the number of oxygen atoms attached by a double bond to chlorine increasess due to `d pi- p pi` back bonding. In other words, stability of the conjugate bases increases in the order : `CIO^(-) lt CIO_(2)^(-) lt CIO_(3)^(-) lt CIO_(4)^(-)`. Thus, due to increase in stability of the conjugate base, acidic strength increases in the same order : `HCIO lt HCIO_(2) lt HCIO_(3) lt HCIO_(4)`. (ii) Oxidizingpower : `HCIO_(4) lt HCIO_(3) lt HCIO_(2) lt HCIO` Reason : As the stability of the oxoanion increases, its tendency to decompose to give`O_(2)` decreases and hence its oxidising power decreases. Sincethe stability of the oxoanion decreases in the order : `ClO_(4)^(-)gt ClO_(3)^(-) gt ClO_(2)^(-) gt ClO^(-)`, therefore, the oxidising power of their oxacids increases in THEREVERSE order, i.e., `HClO_(4) lt HClO_(3) lt HClO_(2) lt HClO`. |
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