Solubility of Solid Compound - Lab Report 1
POST-LAB REPORT
EXPERIMENT 1: SOLUBILITY
PART A: Solubility of Solid Compound
Water | Methyl alcohol | Hexane | |
Benzophenone | White solid remains at the bottom. Insoluble | Dissolve 100% after 20s. Soluble | Dissolve nearly 100% after 55s Soluble |
Tartaric acid | Dissolve 100% after 20s, clear solution. Soluble | Dissolve 100% immediately (~5s). Soluble | Little solid remains. Partially soluble. |
Naphthalene | White solid at the bottom. Insoluble. | About 50% dissolve. Partially soluble. | Dissolve 100% after 10s. Soluble |
Benzophenone
First, the table shows that benzophenone is not soluble in water. This can be explained by the difference in structures of two compound. Water is a high polar molecule due to high electronegativity of oxygen atom. It also can possibly form hydrogen bonding with other compounds because it has an oxygen atom that bonds to a hydrogen atom. Unlike water, benzophenone is a slightly polar molecule because it contains two groups of benzene (hydrocarbon) and only one oxygen atom. As a result, by the rule like dissolves like, benzophenone does not dissolve well in a high polar solvent like water.
However, the polarity of methyl alcohol is lower than water due to group hydrocarbon in its structure, just like benzophenone. Moreover, methyl alcohol also can form hydrogen bonding due to its hydroxide group. As a result, benzophenone can easily dissolve in a polar solvent like methyl alcohol. Next, hexane is also nonpolar, like benzophenone; therefore, benzophenone is soluble in hexane by the rule like dissolves like.
There is a difference of time between the solubility of benzophenone in methyl alcohol and hexane. In methyl alcohol, benzophenone completely dissolves after 20s, but it takes 55s for benzophenone to nearly dissolve 100%. This can be explained that benzophenone can dissolve quickly in methyl alcohol due to the possibility of forming hydrogen bonding of methyl alcohol.
Tartaric acid
Tartaric acid is polar molecule, and it contains four hydroxide groups. Methyl alcohol and water also have hydroxide group that can form hydrogen bonding. As a result, it can easily dissolve in water (after 20s) and methyl alcohol (after 5s). However, in a nonpolar solvent like hexane, its solubility decreases a half.
Naphthalene
Naphthalene is an aromatic hydrocarbon and nonpolar. As the rule like dissolve like, it can dissolve easily in a nonpolar solvent like hexane. However, since water is a high polar molecule, naphthalene is not soluble in water. In methyl alcohol, it is partially soluble because methyl alcohol is a polar molecule.
There is a difference between the solubility of naphthalene and benzophenone in methyl alcohol. In methyl alcohol, naphthalene only dissolves 50%, but benzophenone is completely soluble. This can be explained that both benzophenone and naphthalene consist of two rings of benzene, but benzophenone contains one oxygen atom. Due to this oxygen atom, it can cause the polarity of benzophenone to be higher. Moreover, the existence of oxygen atom with its lone pair can form hydrogen bonding with methyl alcohol.
PART B: Solubility of different alcohols
Water | Hexane | |
1-octanol | First drop: little bubble that is separated from solvent and floats on top of surface, but it is difficult to see 2 layers. The bubble becomes bigger after each drop added. Finally, the mixture forms 2 layers after 20 drops. Insoluble | First drop: clear solution, one layer. After 20 drops, still one layers. Soluble |
1-butanol | 1st drop: mixture is clear, one layer 5th drop: bubbles on top of surface, so it is insoluble after 5 drops added. 10th drop: thin white layer form on top of surface. After 20 drops, 2 layers form. Insoluble. | 1st drop: mixture is clear, one layer. After 20 drops, still clear and 1 layer. Soluble |
Methanol | 1st drop: clear solution, 1 layer. After 20 drops, mixture is still clear and 1 layer. Soluble | 1st drop: clear solution, 1 layer. 5th drop: a clear bubble at the bottom, so it is insoluble after 5 drops added 10th drop: a clear thin layer appears at the bottom. After 20 drops, a second layer form at the bottom. Insoluble |