In order to recrystallize benzoic acid an aqueous solution of sodium hydroxide w
ID: 828789 • Letter: I
Question
In order to recrystallize benzoic acid an aqueous solution of sodium hydroxide was chosen as solvernt. What is the major reason that this solvent is a bad choice for the recrystallization? Explain why you chose your answer!
A)the dielectric constant of aq. NaOH is too high
B)at higher tempreture the solubility of benzoic acid in aq. NaOH is too low.
C)at higher tempretures the solubility of benzoic acid in aq. NaOH is too high.
D)at lower tempretures the solubility of benzoic acid in aq. NaOH is too low.
E)at lower tempretures the solubility of benzoic acid in aq. NaOH is too high.
Explanation / Answer
When you add NaOH solution, and shake vigorously (to ensure a fair equilibrium), then the NaOH deprotonates the benzoic acid, and leaves you with a benzoate ion...this is C6H5COO-. This negatively charge ions is VERY polar, and is virtually insoluble in the ether. It is however Very miscible in the aqueous NaOH solution.
Acid + Base = Salt + Water
Carboxylic acids -COOH react with bases such as NaOH to produce the salt -COONa which is soluble in the water that the NaOH was dissolved in. (The reaction also produces more water).
Benzoic acid reacts with NaOH (depending on the molarity), and becomes an extremely polar ion, which will dissolve in the water that is in the NaOH solution.
ion formation is favoured at high tempreture hence answer A). and C)are correct