Explanation

(a)
$pK_{a}$ value of carboxylic group is less than $pK_{a}$ of [image:12_image429.emf] in amino acid and [image:12_image430.emf] (Z) will have comparatively less $pK_{a}$ than [image:12_image430.emf] (Y) due to –I effect of carboxylic group. We know that acidic strength in inversely proportional to$\ pK_{a}$. Hence, correct order of acidic strength is
[image:12_image431.emf]