Beth Carey Condrey 10/16/2008
Lab 4a Solubility of an Organic Acid, Organic Base, and a Neutral Compound Post Lab Objectives
The purpose of this experiment was to observe the solubility of solids benzoic acid, sodium benzoate, azobenzene, and m-nitroaniline in water, a polar solvent, and ether, a non-polar solvent. Pending the solids solubility in the solvent, hydrochloric acid (HCl) or sodium hydroxide (NaOH) was added to the solution and observations as to whether a reaction had occurred were made.
Observations
This experiment consisted of mixing various organic solids with water and ether and then, if the solid had dissolved, a strong aqueous base or acid. Sodium benzoate was the only compound that dissolved in water; the sodium ion makes this compound an ionic salt, and therefore dissolves in water. When NaOH was added to the aqueous solution of sodium benzoate, no reaction occurred. However, when HCl was added, sodium chloride (salt) precipitated out of the solution. All of the compounds, with the exception of sodium benzoate, dissolved in the diethyl ether. When mixed with the HCl or NaOH, two layers were created with the aqueous solution forming the bottom, heavier layer. In some cases, reactions occurred where the acid would cause the dissolved ions to move to the aqueous layer. These reactions are discussed in greater detail below.
Discussion
Questions during Lab I. A.1. Yes. Benzoic acid is an organic acid, and is therefore dissolvable in organic liquids such as ether. I. A. 2. No reaction occurred when the liquid benzoic acid solution was mixed with HCl. No reaction occurred because a strong acid will not react with organic acids. I. A. 3. A reaction did occur when the liquid benzoic acid solution was mixed with HCl. The organic acid and strong base reacted according to the reaction shown below to produce a water soluble organic salt that was dissolved in the water (non-organic) layer.
I. B. 1. Benzoic acid, an organic acid, does not dissolve in water. Water is a polar, ionic liquid, whereas benzoic acid is non-polar and organic. Organic compounds do not dissolve in water. II. A. 1. No, sodium benzoate did not dissolve in ether. Sodium benzoate is an ionic salt, and therefore would not dissolve in an organic solvent. II. B. 1. Yes, sodium benzoate dissolves in water because it is ionic, an polar salt. Ionic compounds dissolve in water to produce ions. II. B. 2. No reaction occurred when the aqueous sodium benzoate was mixed with the sodium hydroxide. Sodium hydroxide splits into Na+ and OH- ions when mixed with water. These ions can then interact with others found in the solution. In the solution of sodium benzoate, the only ions available to interact with are sodium and benzoate. Na+ will not react with another Na+ ion. No precipitate was formed. II. B. 3. Yes, a reaction occurred when the aqueous solution of sodium benzoate was mixed with HCl. HCl splits into H+ and Cl-. The Cl- and Na+ ions are attracted to eachother, bond, and form NaCl (salt) which then precipitated out of the solution. Normally, NaCl is aqueous in water. However, the ions were present in such strong concentrations that some solid precipitated out of solution. The reaction is shown below.
III. A. 1. Azobenzene, a neutral organic compound, dissolves in ether, because ether is an organic solvent.
III. A. 2. No reaction occurred when NaOH was mixed with the dissolved azobenzene. Azobenzene is a neutral organic compound that will not deprotonate under basic conditions. III. A. 3. No reaction occurred when HCl was mixed with the dissolved azobenzene. Azobenzene is a neutral organic compound that will not protonate under acidic conditions. III. B. 1. No, azobenzene does not dissolve in water because it is an organic compound that is not affected by the polarity of water. IV. A. 1. M-nitroaniline dissolves in ether, because it is an organic compound that is dissolvable by organic solvents such as ether. IV. A. 2. No reaction occurred when NaOH was added to the organic mixture of m-nitroaniline and ether. M-nitroaniline is an organic base, and therefore will not react with a strong base. IV. A. 3. A reaction occurred when HCl was added to the organic mixture of m-nitroaniline and ether. Mnitroaniline is an organic base, and will react with a strong acid to form a water soluble salt. The salt is located in the water layer of the mixture, and the reaction is shown below.
IV. B. 1. M-nitroaniline did not dissolve in water. Organic bases do not dissolve in inorganic, polar solvents. 2. Compound Benzoic Acid Sodium Benzoate Azobenzene m-Nitroaniline Ether Soluble Yes No Yes Yes Aqueous Soluble No Yes No No