Q. The $p{k}_{a}$ of oxoacids of chlorine in water follows the order
KVPYKVPY 2016The p-Block Elements
Solution:
$pK_a$ value of an acid is inversely proportional to acidic strength, i.e. stronger is the acid, lesser will be its $pK_a$ value.
Also, the acidic strength increases with increase in the oxidation number of central atom.
The oxidation number of central atom in given acids are given below.
Acid
Oxidation Number o f central atom
$HCIO$
+1
$HClO_3$
+5
$HClO_2$
+3
$HClO_4$
+7
The acidic strength follows the order,
$ HClO < HClO_2 < HClO_3 < HClO_4$
Thus, the $pK_a$ of oxoacids of chlorine in water,
$HClO_4 < HClO_3 < HClO_2 < HClO$
| Acid | Oxidation Number o f central atom |
|---|---|
| $HCIO$ | +1 |
| $HClO_3$ | +5 |
| $HClO_2$ | +3 |
| $HClO_4$ | +7 |