Question

Given the following Kb values, which cation is the strongest acid?

Base Kb
NH3 1.8 x 10-5
C2H5NH2 5.6 x 10-4
C5H5N 1.7 x 10-9
C8H10N4O2 5.3 x 10-14
(NH2)2CO 1.5 x 10-14
A. NH4+.
B. C2H5NH3+.
C. C5H6N+.
D. [C8H11N4O2]+.
E. [NH2NH3CO]+.

Answer 1

The correct option is E

Step-by-step explanation:

Generally the a base with the highest
`K_b` is the strongest base and from the data given

`C_2H_5NH_2` has the highest value of
`K_b` so
`C_2H_5NH_2` is the strongest base while
`(NH_2)_2CO` has the lowest value of
`K_b` so
`(NH_2)_2CO` is the weakest base

Generally the conjugate acid of a weak base is always a strong acid

So

For
`(NH_2)_2CO` which the weakest base it conjugate acid which is
`[NH_2NH_3CO]^+` will be the strongest acid