Question

The increasing order of $p{K}_b$ value of the following is:

$I.HC\equiv C^{\ominus }II.H^{\ominus }III.\stackrel{\ominus }{N}{H}_{2}IV.\stackrel{\ominus }{C}{H}_3$

• A. IV < III < II < I
• B. I < II < III < IV
• C. IV < II < III < I
• D. I < III < II < IV

Answer 1

The correct option is A IV < III < II < I

Acidity decreases in the order $HC\equiv CH>H_2>N{H}_3>C{H}_4$

Hence, the basicity increases in the order $HC\equiv C^{\ominus }<\stackrel{\ominus }{H}<\stackrel{\ominus }{N}{H}_2<\stackrel{\ominus }{C}{H}_3$

The lower the value of $p{K}_b$, the stronger is the base.

The decreasing order of $p{K}_b$ values is $\stackrel{\ominus }{C}{H}_3<\stackrel{\ominus }{N}{H}_2<H^{\ominus }<HC\equiv C^{\ominus }(IV<III<II<I)$

Hence, the correct option is $A$