Question

Organic Chemictry Lab Post Lab Questions (Acid-Base Extraction)

1.) In this experiment, if the carboxylic acid is benzoic acid, how many moles of benzoic acid are present (assume an equal portion of each component)? How many moles of sodium bicarbonate are contained in 1 mL of a saturated aqueous sodium bicarbonate. Is the amount of sodium bicarbonate sufficient to react with all of the benzoic acid?

2.) To isolate the benzoic acid from the bicarbonate solution, the bicarbonate solution is acidified with concentrated HCl. What volume of acid is required to neutralize the bicarbonate?

3.) The ether solution is extracted with saturated aqueous sodium chloride. What is the purpose of this?

4.) A mixture of benzoic acid and a neutral nonpolar compound is dissolved in ether and mixed thoroughly with aqueous sodium bicarbonate. What is the organic chemical species that is present in the ether layer? In the aqueous layer?

5.) Construct a flow chart that follows the separation of a mixture of 2-nitrophenol (an organic acid not used in this experiment with a pKa = 7.26) and anthracene (neutral organic). Use scheme 1 as a template. Your reagents available are the same ones used in this lab.

Answer 1

1. 1 mol/L x 0.001 L = 0.001 mol (1 mmol) sodium bicarbonate

Therefore, 0.001 mol of Benzoic acid is needed for neutralization. Yes the amount of sodium bicarbonate sufficient to react with all of the benzoic acid.

2. Depends on the concentration of the bicarbonate solution and the hydrochloric acid solution. If their concentrations are equal, it will take a minimum of an equal volume of 0.001L.

3. The ether solution is extracted with saturated aqueous sodium chloride to extract the aqueous phase.