Question

What is the stronger base: ammonia or ethoxide ion?

Answer 1

Hint :According to Arrhenius theory, bases ionize in water to yield hydroxide ions (\[O{H^ - }\]) . According to Brønsted-Lowry theory, base is any species that is capable of accepting a proton, which requires a lone pair of electrons to bond to the \[{H^ + }\].

Complete Step By Step Answer:
There is a relationship between the strength of an acid (or base) and the strength of its conjugate base (or conjugate acid) and that is
 The stronger the acid, the weaker its conjugate base. The weaker the acid, the stronger its conjugate base.
 The stronger the base, the weaker its conjugate acid. The weaker the base, the stronger its conjugate acid.
Now, ethanol is a weak acid
\[C{H_3}C{H_2}OH + {H_{_2}}O \rightleftarrows C{H_3}C{H_{_2}}{O^ - } + {H_3}{O^ + }\] \[{K_a} = 1 \times {10^{ - 16}}\]
\[C{H_3}C{H_{_2}}{O^ - }\] (ethoxide ion) is the conjugate base of \[C{H_3}C{H_2}OH\](ethanol), which is the strong base.
\[C{H_3}C{H_{_2}}{O^ - } + {H_3}{O^ + } \rightleftarrows C{H_3}C{H_2}OH + {H_{_2}}O\] In case of ammonia, it is a weak base
\[N{H_3} + {H_2}O \rightleftarrows NH_4^ + + O{H^ - }\] \[{K_b} = 1.8 \times {10^{ - 5}}\]
Hence, it is clear from the above discussion of dissociation constant values that ethoxide ion is a stronger base than ammonia.

Additional Information:
Ethoxide ion carries a negative charge and hence can easily accept \[{H^ + }\]ion. Whereas ammonia is a neutral molecule.
 Ethoxide ion has three lone pairs that can accept a proton, compared with only one lone pair for ammonia.
A strong base completely ionizes in water to give its conjugate acid and \[O{H^ - }\]ion.

Note :
 The basic nature of the species is inversely proportional to the stability of the species. More the tendency of the base to accept \[{H^ + }\]ion, greater is its basic strength.