Question

When pure ammonium chloride is dissolved in pure water, the pH of the resulting solution is not 7. This is because:
A. ammonium ions accept protons from water molecules leaving free $OH^-$ ions in the solution
B. ammonium ions donate protons to water molecules forming $H_30^+$ ions in the solution
C. ammonium ions combine with water molecules to give the weak base, ammonium hydroxide
D. chloride ion make the solution acidic

Answer 1

The negative logarithm of a hydrogen ion concentration is called ${{pH}}$. The ${{pH}}$ decreases when the solution becomes acidic and ${{pH}}$ increases when the solution becomes basic. ${{pH}}$ scale is used to help to find out the acidity or basicity of the solution.

Complete step by step answer:
When you dissolve solid ammonium chloride, ${{N}}{{{H}}_{{4}}}{{Cl}}$ in water $\left( {{{{H}}_{{2}}}{{O}}} \right)$, the ammonium chloride decomposes into its component ions, ${{NH}}_{{4}}^{{ + }}$ and ${{C}}{{{l}}^{{ - }}}$. The chemical reaction undergoing dissociation is,
${{N}}{{{H}}_{{4}}}{{Cl}}\,\,{{ + }}\,\,{{{H}}_{{2}}}{{O}}\,\, \to \,\,{{{H}}_{{3}}}{{{O}}^{{ + }}}\,\,{{ + }}\,\,{{N}}{{{H}}_{{3}}}\,\,{{ + }}\,\,{{C}}{{{l}}^{{ - }}}$
Acids are substances that donate protons and bases are substances that accept protons. Ammonium donates protons to the water molecule. This makes the solution become slightly acidic. This causes a decrease in the ${{pH}}$, due to the formation of ${{{H}}_{{3}}}{{{0}}^{{ + }}}$ ions.
Ammonium chloride is a commercially important compound. It is used in fertilizers as a nitrogen source in it. It can be used as medicine .It can be used as glue for binding plywood. It also finds application in electrochemistry, used in Leclanche cells in aqueous solutions. It is used in food additives ie, in making of bread and as a yeast nutrient. It is used as an acidifier. They are used as buffer solutions along with ammonia. It is given to cattle as feed supplements.

So, the correct answer is Option B.

Note: Buffer Solution is an aqueous it consists of a mixture containing a weak acid and the conjugate base of the weak acid, or a weak base and the conjugate acid of the weak base. They resist a change in pH on the addition of small amounts of acid or alkali to them.
The classical concept of acid and bases was developed by Arrhenius. Arrhenius acid is a substance which has a hydrogen atom and easily gives hydrogen ion or proton in its aqueous solution. Arrhenius base is a substance that donates hydroxyl ions in its aqueous solution.