Arrange the following in decreasing order of acidic nature of
(a) (i) `F_(3) C C H_(2) OH` , (ii) `(CH_(3))_(3) C C H_(2) OH` , (iii) `FCH_(2) CH_(2) C_(2) OH`
(b)

Explanation

(a) `(i) gt (iii) gt (ii)`
(b) `(ii) gt (i) gt (iii) gt (iv)`
`-NO_(2) ` is stabilizing by strong electron withdrawing nature, `-CH_(3)` is destabilizing by electron donating nature (+ 1) and `-OCH_(3)` is also destabilizing due to electron donting nature (+ R , - 1)