Solubility of Compounds in Sodium Bicarbonate Solution

Sodium bicarbonate (NaHCO3) is a weak base and can be used to test the solubility of compounds in water. It reacts with acidic compounds to produce carbon dioxide gas, which can be observed as effervescence. Compounds that are soluble in sodium bicarbonate solution will produce effervescence when reacted with it.

Out of the given options, o-nitrophenol will not be soluble in sodium bicarbonate solution. This is because:

- o-Nitrophenol is a weak acid with a pKa value of 7.15. It can undergo deprotonation in the presence of a strong base like sodium hydroxide (NaOH) to form the corresponding salt. However, sodium bicarbonate is a weaker base than NaOH and cannot fully deprotonate o-nitrophenol.
- o-Nitrophenol has a nitro group (-NO2) attached to the phenol ring, which makes it more acidic and less soluble in water. The presence of the nitro group also hinders the formation of hydrogen bonds between o-nitrophenol and water molecules, further reducing its solubility.
- When o-nitrophenol is added to sodium bicarbonate solution, it does not produce effervescence, indicating that it is not soluble in the solution.

On the other hand, the other options have the following properties that make them soluble in sodium bicarbonate solution:

- 2,4,6-Trinitrophenol (picric acid) is a strong acid that can undergo deprotonation in the presence of sodium bicarbonate to produce effervescence.
- Benzoic acid is a weak acid with a pKa value of 4.2. It can undergo partial deprotonation in the presence of sodium bicarbonate to produce effervescence.
- Benzenesulphonic acid is a strong acid that can undergo deprotonation in the presence of sodium bicarbonate to produce effervescence.

Therefore, the correct answer is option C, o-nitrophenol, which will not be soluble in sodium bicarbonate solution.

While 2,4,6-trinitrophenol, benzoic acid and benzene sulphonic acid are soluble in nahco3. this reaction is possible in the forward direction if acid is more acidic than h2co3. o-nitrophenol is less acidic than h2co3. hence, it is not soluble in sodium hydrogen carbonate.