Chemicals are often labelled as ‘acids’ or ‘bases,’ which depends on the pH of the chemicals involved. Acids typically have a pH that is less than 7 while bases have a pH of 7 or more. The purpose of the laboratory experiment was to identify ionic, organic, or organic acids by dissolving unknown chemicals in solutions and noting down the resulting reactions. Another objective of the exercise was to test the solubilities of the compounds to help plan the separation scheme. Finally, the last objective of the exercise was to weigh each compound, computer percent recovery, and complete identity confirmation tests. The laboratory exercise also included identifying which chemicals dissolved in sodium nitrate (NaNO 3 ), fluorine (C 13 H 10 ), or m-toluic acid (C 8 H 8 O 2 ) from vial #7. The compounds involved include NaNO 3 , which is an ionic compound with a melting point of 308°C and is soluble. C 13 H 10 is soluble as well and is organic. It has a melting point of 116°C. C 8 H 8 O 2 is an organic acid, is soluble, and has a melting point of 113°C. The overall objectives will be accomplished by testing the solubilities of the chemicals in the three compounds mentioned earlier. The phrase “like dissolves like” applies to this project because it pertains to acids dissolving in acids and bases dissolving in bases. Thus, water will not dissolve in oil, for example.
Results
Table 1. Lewis Structures
| Compound Name | Lewis Structure |
| NaNO 3 |
Na + O N O- O- |
| C 13 H 10 | |
| C 8 H 8 O 2 |
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m-toluic acid (s)
Heated
m-toluic acid (in ethanol)
Fluorine (solid)
Filtered
Sodium Nitrate (solid)
Add denatured ethanol (40 mL)
Boil
m-toluic acid, fluorine
Sodium Nitrate (aqueous)
Filtered
Add 50 mL of H 2 O
Table 3. Percent Recovery
The percent recovery calculation for each compound is shown below:
| Compound | Calculation | Percent Recovery |
| NaNO 3 | 2.09 g/ 2.00 g x 100 | 104.5% |
| C 13 H 10 | 1.51 g/ 2.00 g x 100 | 75.5% |
| C 8 H 8 O 2 | 2.07 g/ 2.00 g x 100 | 103.5% |
Table 4. Confirmation Tests
| Compound | Dissolved in |
| Ionic compound (NaNO 3 ) | H 2 O |
| Organic Compound (C 13 H 10 ) | Acetone, toluene |
| Organic Acid (C 8 H 8 O 2 ) | Denatured ethanol, acetone, toluene, and methane |
Discussion
There are three types of intermolecular forces in pure substances. These include the London dispersion force (LDF), which is the weakest of the intermolecular forces. The LDF is the force that is created between two non-polar molecules. In this force, the electrons of one molecule are attracted by the other molecule’s nucleus while it is repelled by the molecule’s electrons. The next type of intermolecular force is the dipole-dipole interaction, which occurs whenever two polar molecules are proximal to each other. The positive charge of the one molecule is attracted by the negative charge of the other molecule. Many molecules exist in polarity; therefore, this type of intermolecular force is common. Another type of intermolecular bonds are hydrogen bonds, which occurs when hydrogen atoms become bonded to electronegative atoms, such as F, N, or O. These tend to exhibit strong intermolecular interactions.
The intermolecular forces for the organic compound and organic acid differ. For organic compounds, dipole-dipole interactions are the most common because polar covalent bonds have the characteristic of bonded atoms, which have localized charges that are fractional in nature and that are equal but opposite. Dipole-dipole interactions are substantially weaker than the relationship between two ions. In addition, the attractive interaction between dipoles decreases with increasing distance. For organic acids, the most common intermolecular forces are hydrogen bonds. Hydrogen bonds are usually stronger than other bonds are produce acids. These intermolecular forces determine the solubility and boiling points of substances.
The separation of the compounds in this laboratory experiment can be summarized as follows: the compounds are all in vial #7 and are mixed together. Then, they are dissolved in water and then filtered. The ionic compounds can be dissolved in H 2 O. The organic compound, which is fluorine, can be dissolved in acetone and toluene. Lastly, the organic acid can be dissolved in denatured ethanol, acetone, toluene, and methane. This shows that the organic acid is the most soluble of the three chemicals.
The percent recovery for each compound, shown in Table 3, shows how much of the compound was recovered after dissolving, filtration, and heating. The percent recovery of sodium nitrate (104.5%) is the highest among the three chemicals because it was completely dissolved in H 2 O. The percent recovery for fluorine is the lowest because it both soluble and organic (75.5%). Lastly, the percent recovery for m-toluic acid is intermediate because it was soluble in nearly all substances. One error that was encountered was during the handling of the m-toluic acid, which caused the percent recovery to be low. However, this error did not affect the experiment at all. The confirmation tests that were done show which compounds are acids, organic compounds, and organic acids. These tests depend on the solubility and boiling points of the chemicals that were tested, as well as the solvents.
The laboratory experiment was successful because the objectives of the experiment were met. The chemicals were identified through their solubility, their boiling points, and their percent recovery. In addition, the experiment was successful because it was proven that different compounds with different intermolecular forces can be tested and separated by dissolving them in various other solvents. Thus, the compounds can be identified through the solvents that were used to dissolve them.
