Identification of Compound Failing to Liberate Carbon Dioxide with Sodium Bicarbonate
Identify which of the following compounds will NOT liberate gas upon reaction with an aqueous solution of sodium bicarbonate:
Options
A
Benzoic acid
B
Benzenesulphonic acid
C
Salicylic acid
DCorrect
Carbolic acid (Phenol)
Topics & Concepts
Step-by-Step Solution
To determine which compound does not liberate upon reaction with an aqueous solution of sodium bicarbonate (), we consider the acid-base equilibrium involved:
An acid () can decompose sodium bicarbonate to liberate carbon dioxide () only if it is a stronger acid than carbonic acid (), which has a of approximately . In other words, the acid must have a .
Let us examine the values of the given compounds:
- Benzenesulphonic acid (): It is a strong mineral-like acid with . Since , it readily reacts with to liberate .
- Salicylic acid (): The ortho-hydroxy group stabilizes the conjugate base through intramolecular hydrogen bonding (the ortho-effect), giving it a . Since , it liberates .
- Benzoic acid (): A carboxylic acid with . Since , it decomposes to liberate .
- Carbolic acid (Phenol, ): A very weak acid with . Because its is substantially greater than that of carbonic acid (), phenol is a weaker acid than . The acid-base equilibrium lies heavily to the left, meaning it fails to decompose and therefore does NOT liberate gas.
Thus, carbolic acid (phenol) does not liberate .
Correct Option: (D)