Question

Find pH of an aqueous solution of $N{H_4}Cl$ ?
(A) 7
(B) $>7$
(C) $<7$
(D) 1

Answer 1

The first term to understand here is pH, which represents potenz hydrogen, or power of hydrogen. Thus, pH scale is a good way of representing whether a substance is acidic or basic.
The next thing to understand is that ammonium chloride which is salt is made up of $HCl$ acid which is strong and $N{H_4}OH$ base which is a weak base.

Complete step by step answer:
Now, since ammonium chloride is salt, it will dissociate into its constituents ions as $N{H_4}^ +$ and $C{l^ - }$ ions. The reaction can be written as:
$N{H_4}C{l_{(s)}}\xrightarrow{{{H_2}O}}N{H_4}{^ + _{(aq)}} + C{l^ - }_{(aq)}$
Now, the water present will also have ions, ${H^ + }\& O{H^ - }$
These ions will combine to give respective acid and base according to following equations of strong acid formation and weak base formation.
${H^ + } + C{l^ - } \to HCl$
As we know, the hydrochloric acid formed is strong acid, that means it will never be formed, and break into ions.
While, the formation of base takes place in the way shown below:
$N{H_4}OH \rightleftharpoons N{H_4}^ + + O{H^ - }$
Here, the reaction is an example of equilibrium. We already know that for weak bases, the base dissociates into very less ions. Thus more Ammonium hydroxide is formed as it is a weak base, so does not dissociate into ions.
Hence we will get more amounts of ${H^ + }$ ions, thus making the solution slightly acidic.
If we see pH scale, then 7 is the neutral value, >7 is basic solution, <7 is acidic solution.
So, option (A), and (B) cannot be the correct options, even (D) is not correct as the solution has salt, and salt cannot have pH value of 1, which is given to pure strong acid.
Thus, the correct option is (C) <7
Thus the above statement is true, hence the correct option is (A) True.

Note:
We should know the definition of weak acids, weak bases, strong acids and strong bases.
These weak and strong words represent the dissociation of solution. These words are used only in
reference to acids and bases, while salts are always strong electrolytes and give ions immediately
after dissolving in water.
Examples: Strong acid- $HCl$
Weak acid- $C{H_3}COOH$
Strong base- $NaOH$
Weak base- $N{H_4}OH$