Question

${\text{N}}{{\text{H}}_{\text{4}}}{\text{OH}}$ is a weak base because:
${\text{(A)}}$ It is completely ionized
${\text{(B)}}$ It has low vapour pressure
${\text{(C)}}$ It has low density
${\text{(D)}}$ It is only partially ionized

Answer 1

Acid is classified into two types, strong acid and weak acid and just like the acid base is also classified into two types strong base or weak base. Strong bases ionize completely in ${{\text{H}}_{\text{2}}}{\text{O}}$ to produce ${\text{O}}{{\text{H}}^{\text{ - }}}$ ions whereas weak bases ionize partially. Similarly strong acid ionize completely in ${{\text{H}}_{\text{2}}}{\text{O}}$ to produce ${{\text{H}}^{\text{ + }}}$ ions and weak acid ionize partially to give ${{\text{H}}^{\text{ + }}}$ ions.

Complete step by step answer:

Weak base are not completely ionized in ${{\text{H}}_{\text{2}}}{\text{O}}$ therefore option ${\text{(D)}}$ is the correct answer. Ammonia doesn't contain ${\text{O}}{{\text{H}}^{\text{ - }}}$ ions, but it reacts with ${{\text{H}}_{\text{2}}}{\text{O}}$ to form ammonium ions and hydroxide ions.
There, the correct option is D, that is it is only partially ionized.

Additional information:
Ammonium hydroxide forms insoluble hydroxides when treated with certain metallic salt solutions. The insoluble hydroxide formed gets precipitated in the form of a precipitate and may be identified by their distinct colors. Some precipitated metallic hydroxide become soluble in addition to excess ammonium hydroxide. This is due to the formation of a soluble complex salt in the presence of ammonium hydroxide in excess.
The action of ammonium hydroxide on calcium salt solution is briefly described below:
Calcium salt solutions are colourless and consist of ${\text{C}}{{\text{a}}^{{\text{2 + }}}}$ ions. When ammonium hydroxide is added to a calcium salt solution, a dull white precipitate of calcium hydroxide is obtained. This precipitate remains almost insoluble in the presence of ammonium hydroxide in excess. For example,
${\text{CaC}}{{\text{l}}_2} + {\text{2N}}{{\text{H}}_{\text{4}}}{\text{OH}} \to {\text{ Ca(OH}}{{\text{)}}_2} + {\text{2N}}{{\text{H}}_{\text{4}}}{\text{Cl}}$

Note:
Acidic solutions have a ${\text{pH}}$ value below ${\text{7}}$and ${\text{pH}}$ value more than ${\text{7}}$ are basic solution. Ammonium hydroxide is a weak base so it can be used for the treatment of bee’s sting because bees sting has formic acid which can be neutralized by ammonium hydroxide.