Read the passage carefully and answer the Questions.

Carboxylic acids are the earliest organic compounds isolated from nature. These are also known as organic acids but are weaker acids as compared to mineral acids. However, they are more acidic than alcohols and phenols because of greater resonance stabilization of the parent acid and its conjugate base. The acidic strength is determined by the Ka, which is called the acidity constant. The greater the value of Ka, the greater the tendency of the acid to ionize and hence the stronger the acid. The acidic strength of the saturated aliphatic carboxylic acid depends upon the inductive effect and its position with respect to - COOH groups. Electron-donating substituents tend to decrease whereas electron -withdrawing substituents tend to increase the acidic strength. The acidic strength of the aromatic carboxylic acid, on the other hand depends upon both the inductive effect and the resonance effect of the substituents.

How can we express the (acidity constant) '$K_a$' of RCOOH?

$K_a = [RCOO^-][H_3O^+]/ [RCOOH]$

The correct answer is Option (2) → $K_a = [RCOO^-][H_3O^+]/ [RCOOH]$

For a carboxylic acid:

$RCOOH + H_2O <=> RCOO^- + H_3O^+$

The acid dissociation constant (Ka) is defined as:

$K_a = \frac{[{RCOO^-}][{H_3O^+}]}{[{RCOOH}]}$

It measures the extent of ionization of the acid in water.