Q. Which is decreasing order of strength of bases? $\overline{O}H,\overline{N}H_{2},HC \equiv C^{-}\ and\ CH_{3}CH_{2}^{-}$
A) $H_{3}CCH_{2}^{-} > NH_{2}^{-} > HC \equiv C^{-} > OH^{-}$
B) $HC \equiv C^{-} > CH_{3}CH_{2}^{-} > NH_{2}^{-} > OH^{-}$
C) $OH^{-} > NH_{2}^{-} > CH \equiv C^{-} > H_{3}CCH_{2}^{-}$
D) $NH_{2}^{-} > HC \equiv C^{-} > OH^{-} > H_{3}CCH_{2}^{-}$
Explanation
(a)
The conjugate acids of $\overline{O}H,\overline{N}H_{2},HC \equiv C^{-}\ and\ CH_{3}CH_{2}^{-}$ are
$H_{2}O,NH_{3},HC = CH\ \ and\ CH_{3} - CH_{3}$respectively. Their acidic strength is as $HOH > HC \equiv CH > NH_{3} > CH_{3}CH_{3}$
A strong acid has a weak conjugate base, hence the decreasing order of basic strength is
$CH_{3}CH_{2}^{-} > NH_{2}^{-} > HC \equiv C^{-} > OH^{-}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.