Question

Which of the following salt is basic?
A. $HOCl$
B. $NaOCl$
C. $NaHS{O_4}$
D. $N{H_4}N{O_3}$

Answer 1

Hint:
We can define acids and bases by using different theories but in all cases, their neutralization reaction gives salt as the product that can also be acidic, basic or neutral in nature.


Let’s start by having a brief look at the different theories that can be used to define acids and bases:

- Arrhenius theory: As per this theory, acids $\left( {HA} \right)$ and bases $\left( {BOH} \right)$ can be defined as ${H^ + }$ and $O{H^ - }$ donors respectively. The involved chemical equations for the same can be written as shown below:
$
HA \mathbin{\lower.3ex\hbox{$\buildrel\textstyle\rightarrow\over
{\smash{\leftarrow}\vphantom{_{\vbox to.5ex{\vss}}}}$}} {H^ + } + {A^ - }\\
BOH \mathbin{\lower.3ex\hbox{$\buildrel\textstyle\rightarrow\over
{\smash{\leftarrow}\vphantom{_{\vbox to.5ex{\vss}}}}$}} {B^ + } + O{H^ - }
$

- Brönsted-Lowry theory: As per this theory, we can define acids and bases as ${H^ + }$ donors and ${H^ + }$ acceptors respectively. The involved chemical equations for the same can be written as shown below:
$
{H_2}O \mathbin{\lower.3ex\hbox{$\buildrel\textstyle\rightarrow\over
{\smash{\leftarrow}\vphantom{_{\vbox to.5ex{\vss}}}}$}} {H^ + } + O{H^ - }\\
N{H_3} + {H^ + } \mathbin{\lower.3ex\hbox{$\buildrel\textstyle\rightarrow\over
{\smash{\leftarrow}\vphantom{_{\vbox to.5ex{\vss}}}}$}} NH_4^ +
$
This theory also gave rise to the concept of conjugate acid-base pairs which differ by one ${H^ + }$. As we can see in the above examples, ${H_2}O \, {\rm{ and }} \, O{H^ - }$are acid and conjugate base respectively.

- Lewis acids–base theory: As per this theory, acids and bases can be defined as electron pair acceptors and donors respectively. We can say that Lewis acids include not just ${H^ + }$ donors but also those which might not have ${H^ + }$yet act as acids by accepting electrons. For example $B{F_3}$ .
We know that the product of neutralization reaction of acid and base is salt and water. We can write a general chemical equation for this as follows:
$HA\left( {acid} \right) + BOH\left( {base} \right) \mathbin{\lower.3ex\hbox{$\buildrel\textstyle\rightarrow\over
{\smash{\leftarrow}\vphantom{_{\vbox to.5ex{\vss}}}}$}} BA\left( {salt} \right) + {H_2}O\left( {water} \right)$

We can further classify acids and bases as weak and strong on the basis of the value of their dissociation constants. It has also been established that in a conjugate acid-base pair, one would be strong and another would be weak. So, the conjugate base of a strong acid would be weak and vice versa. Similarly, conjugate acid of a strong base would also be weak and vice versa. Depending on the strength of the involved acid and base, we can deduce the nature of the salt.

Now, let’s have a look at the given compounds one by one: $HOCl$ is a weak acid; $NaOCl$ is a salt of $NaOH$ and $HOCl$; $NaHS{O_4}$ is a salt of $NaOH$ and $HSO_4^ - $ and $N{H_4}N{O_3}$ is a salt of $N{H_4}OH$ and $HN{O_3}$.
As we can see that first one is not even a salt, second one is a salt of strong base and weak acid, third one still has ionizable protons and last one is a salt of weak base and strong acid.

Hence, the answer should be option B.

Note:
We have to be careful while deciding the nature of salt as even if one is a salt of strong base but having an ionizable proton makes it acidic in nature.