Question

Which of the following salts does not show its correct nature mentioned against it?
A.$KBr$ solution- Neutral
B.$NaCN$ solution- Acidic
C.$N{H_4}N{O_3}$ solution- Acidic
D.$KF$ solution- Basic

Answer 1

Salts break into ions in aqueous solutions and their hydrolysis may result into the formation of ${H^ + }$ or $O{H^ - }$ ions. To answer this question, you must recall the acids and bases that undergo neutralization to form the salts given.

Complete step by step answer:
We can say that,
When a strong acid is neutralized by a strong base, a neutral salt is formed. When a strong acid reacts with a weak base, the reaction yields an acidic salt. Similarly when a weak acid reacts with a strong base, a basic salt is formed. We cannot directly comment about the nature of the salt of a weak acid and a weak base. For this, we need to have the $p{K_a}$ and $p{K_b}$ values of the acid and the base respectively.
A.$KBr$
It is prepared by the reaction of $KOH + HBr$ which are a strong base and strong acid respectively. Thus it is neutral.
B.$NaCN$
It is prepared by the reaction of $NaOH + HCN$ which is a strong base and weak acid pair. Thus the salt is basic and is wrongly matched.
C.$N{H_4}N{O_3}$
It is prepared by the reaction of $N{H_4}Cl + HN{O_3}$ which is a strong acid and weak base pair. Thus, the salt is acidic and is correctly matched
D.$KF$
It is prepared by the reaction of $KOH + HF$ which is a strong base and weak acid pair. Thus the salt is basic and is correctly matched.

Thus, the correct answer is B.

Note:
Acidic salts are those salts which are considered to have a $pH < 7$ in aqueous solutions. This happens because of the presence of acidic hydrogen ions that may be left unreacted while the neutralization reaction occurs resulting in the formation of salt.
Similarly basic salts are those salts which are considered to have a $pH > 7$ in aqueous solutions. This happens because of the presence of basic hydroxide ions that may be left unreacted while the neutralization reaction occurs resulting in the formation of a salt.