a. One can use pH differences to separate basic substances from non-basic ones. Which of the following would be suitable for use in the aqueous phase to achieve the separation of phenol from naphthalene: K2HPO4, K3PO4, (CH3)3NHCl, (CH3)3N, NaHCO3, Na2CO3? Explain your answer.
b.Which of these same materials (K2HPO4, K3PO4, (CH3)3NHCl, (CH3)3N, NaHCO3, Na2CO3) could be used in the aqueous phase to separate phenol from benzoic acid?
a. To separate phenol from naphthalene based on their pH differences, we need to select a suitable substance to adjust the pH of the aqueous phase. Phenol is a weak acid and naphthalene is non-basic. Therefore, we require a basic substance that will ensure phenol remains in the aqueous phase while naphthalene stays in the organic phase.
Out of the given materials, K2HPO4, K3PO4, (CH3)3NHCl, (CH3)3N, NaHCO3, and Na2CO3, the suitable choice would be Na2CO3 (sodium carbonate).
Here's the reasoning:
1. K2HPO4 and K3PO4 are phosphate salts and do not possess basic properties that can adjust the pH properly for this separation.
2. (CH3)3NHCl and (CH3)3N are organic compounds known as trimethylamine and trimethylammonium chloride. Though they are basic substances, they are not suitable for this separation as they may form emulsions due to their organic nature.
3. NaHCO3 (sodium bicarbonate) is a weak base that can partially adjust the pH, but it may not be strong enough to ensure complete separation of phenol from naphthalene.
4. Finally, Na2CO3 (sodium carbonate) is a strong base that can effectively adjust the pH of the aqueous phase. It will keep phenol in the aqueous phase as a sodium phenolate while allowing naphthalene to remain in the organic phase. Hence, Na2CO3 is the most suitable option.
b. To separate phenol from benzoic acid based on their pH differences, we need to select a suitable substance to adjust the pH of the aqueous phase. Phenol is a weak acid, while benzoic acid is a stronger acid. Therefore, we require a basic substance that will allow phenol to remain in the aqueous phase while protonating benzoic acid.
Out of the given materials, K2HPO4, K3PO4, (CH3)3NHCl, (CH3)3N, NaHCO3, and Na2CO3, the suitable choice would be NaHCO3 (sodium bicarbonate).
Here's why:
1. K2HPO4 and K3PO4 are phosphate salts and do not possess basic properties that can adjust the pH properly for this separation.
2. (CH3)3NHCl and (CH3)3N, being organic bases, may not be able to completely separate benzoic acid from phenol due to the formation of emulsions.
3. Na2CO3 (sodium carbonate) is a stronger base than what is required to separate phenol from benzoic acid. It may cause the formation of sodium benzoate, making it difficult to achieve a complete separation.
4. NaHCO3 (sodium bicarbonate) is a weak base that can adjust the pH to selectively protonate benzoic acid in the aqueous phase. This will allow phenol to remain in its original form, making NaHCO3 the most suitable option for separating phenol from benzoic acid.