# What is the decreasing order of strength of the bases $OH^-, NH_2^- , H-C\equiv C^-$ and $CH_3CH_2^-$ ?

(a) $CH_3CH_2^- > NH^-_2 > H-C \equiv C^- > OH^-$

(b) $H-C\equiv C^- > CH_3-CH^-_2 > NH_2^- > OH^-$

(c) $OH^- > NH^-_2 > H-C\equiv C^- > CH_3-CH^-_2$

(d) $NH^-_2 > H-C\equiv C^- > OH^- > CH_3CH_2^-$.

Toolbox:
• A weak acid has a strong conjugate base.
Answer: $CH_3CH_2^- > NH^-_2 > H-C \equiv C^- > OH^-$

Since the acidic nature decreases in the order: $H_2O > H-C\equiv C-H > NH_3 > CH_3 - CH_3$
Therefore, the conjugate base strength follows the order: $CH_3CH_2^- > NH^-_2 > H-C \equiv C^- > OH^-$