Lab 4-Acid Base Extraction

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

Aqueous sodium chloride is a drying solution that helps removes all traces of water from the organic solution before it is evaporated in the backwashing step.

A mixture of benzoic acid and naphthalene was dissolved in tert-butyl methyl ether and the resulting solution was extracted with aqueous sodium bicarbonate. The major organic species (excluding solvent) that is present in the lower layer is

Benzoic acid reacts with sodium bicarbonate to produce the sodium salt of benzoic acid (sodium benzoate). Although benzoic acid is more soluble in ether than in water, the salt of benzoic acid, being ionic and very polar, is more soluble in water than in ether. The denser lower water layer will thus contain the sodium benzoate. The upper ether layer will contain the naphthalene.

A mixture of benzoic acid and naphthalene was dissolved in tert-butyl methyl ether and the resulting solution was extracted with aqueous sodium bicarbonate. The major organic species (excluding solvent) that is present in the upper layer is

Benzoic acid reacts with sodium bicarbonate to produce the sodium salt of benzoic acid (sodium benzoate). Although benzoic acid is more soluble in ether than in water, the salt of benzoic acid, being ionic and very polar, is more soluble in water than in ether. The denser lower water layer will thus contain the sodium benzoate. The upper ether layer will contain the naphthalene.

A sample of naphthalene was mixed with water and tert-butyl methyl ether. The naphthalene dissolved mostly in the ___________(water or ether?) layer. The ether layer was the _________ (upper or lower?) layer.

Ether, upper Naphthalene, being relatively nonpolar, will be more soluble in ether than in water.tert-Butyl methyl ether, with a density of 0.74, will float on top of water (density = 1.0).

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?

1 mL of sodium bicarbonate, which is 0.001 mol, as calculated in the previous problem is used. Concentrated HCL has a molarity of 12 M (12 mol/L), therefore the following equation can be used to find the volume of HCL is needed, assuming 30 drops is equal to 1 mL. = 0.001 mol x (1 L/ 12 mol) x (1000 mL / 1 L) = 0.083 mL of concentrated HCL or 2.5 drops (0.083 mL x (30 drops/ 1 mL) = 2.5 drops)

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?

The molar mass of benzoic acid is 122.12 gram (g)/mole (mol), the initial mass of benzoic acid is 0.125 g according to the handout. We can calculate mols of benzoic acid in the following equation. = 0.125 g x (1 mol/ 122.12 g) = 0.00102 mols benzoic acid Using the information in the handout, the molarity (M) of sodium bicarbonate saturated in a aqueous solution is 1 M or 1 mol/ 1 L. Therefore, the following equation can be used to calculate the number of mols of sodium bicarbonate present in 1 mL. = 1 mL x (1 L/ 1000 mL) x (1 mol/ 1 L) = 0.001 mols sodium bicarbonate. The amount of sodium bicarbonate (0.001 mol) is slightly less than the benzoic acid (0.00102 mol by a value of 0.00002 mol, so that can be considered negligible. The amount of sodium bicarbonate should be sufficient to react with all the benzoic acid.

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?

The neutral nonpolar compound would be present in the ether layer, since it's non-polar it will be soluble in ether. Benzoic acid will react with sodium bicarbonate to form sodium benzoate (benzoic acid sodium salt) which will be present in the aqueous layer, since it is polar and therefore water soluble.

Which of the following organic solvents would be suitable for use in the extraction of an aqueous solution? methanol acetone hexane ethanol

hexane One requirement of an extraction solvent is that it be mostly insoluble in water (the other solvent). Methanol, ethanol, and acetone are completely soluble in water. Hexane has a very low solubility in water.

A mixture of benzoic acid and naphthalene was dissolved in tert-butyl methyl ether and the resulting solution was extracted with aqueous sodium bicarbonate. The lower layer was separated and to it was added concentrated hydrochloric acid, upon which a white precipitate formed. What was the structure of the precipitate?

mixture of benzoic acid and naphthalene was dissolved in tert-butyl methyl ether and the resulting solution was extracted with aqueous sodium bicarbonate. The lower layer was separated and to it was added concentrated hydrochloric acid, upon which a white precipitate formed. What was the structure of the precipitate?

When two liquids that are mostly insoluble in one another are mixed together, they separate out into two layers. Whether one liquid is the upper or lower layer depends upon the relative densities of the two liquids. the solubilities of the two liquids. functional groups present. molecular weights of the two liquids.

relative densities of the two liquids.

Decaffeinating coffee or tea represents the following type of extraction: solution into another solvent solid into a solvent solid into a solid solvent into a solid

solution into another solvent

A sample of glucose is added to a mixture of water and tert-butyl methyl ether. The glucose will dissolve mostly in the _________ (ether or water?) layer. The water layer will be the ____________ (upper or lower?) layer?

water, lower Glucose, with its -OH groups, is very polar and is also capable of forming hydrogen bonds. It will therefore be more soluble in water than in the relatively less polar ether. tert-Butyl methyl ether (density = 0.74) will float on water (density = 1.0).