GENERAL CHEMISTRY 2 CHM02/G203
Experiment 2: Effect of Nature of Solute and Solvent on Solubility
PDS: Front Page: Discussion:
2016142427 Group 6
Conclusion: Total:
Discussion Solute
𝐻2 𝑂
Kerosene
𝑁𝑎𝐶𝑙 (Salt/Sodium Choride)
Soluble
Insoluble
𝐶10 𝐻8 (Napthalene)
Insoluble
Soluble
Solvents are solutes are both classed as polar and non-polar. In order to form a solution the right kind of solute must dissolve in the right kind of solvent, otherwise, no solution will be formed. This experiment was conducted to determine the effects of the nature of solvents and solutes, whether it is polar or non-polar, in solubility. Before the experiment started, the students were tasked to gather the materials from SR2. After gathering the materials, the experiment was commenced. On the first part of the experiment the prepared solutes, sodium chloride and naphthalene, were put into two separate micro test tubes. Each of the solutes weighs 0.15 grams. Using droppers, 20 drops of water were added to both of the solutes. Both were stirred and observed if the solutes dissolved in water. Sodium chloride dissolved completely while naphthalene did not dissolve at all. This process was repeated, but instead of water, kerosene was used. It was observable that kerosene dissolved naphthalene, but did not dissolve sodium chloride. The explanation for that phenomenon was the nature of the solutes and the solvents. In the first setup, water dissolved sodium chloride because they were both polar. Sodium chloride’s negative and positive ions were separated and were attracted to their opposites in water. Positively charged sodium ion was attracted to negatively charged oxygen while negatively charged chloride ion was attracted to positively charged hydrogen. In short there is a dipole-
dipole interaction between the molecules. This phenomenon cannot occur between water and naphthalene because water is polar while naphthalene is non-polar. On the other hand, in the second setup both kerosene and naphthalene are non-polar, thus forming a uniform solution. This is explained by dispersion forces between the two, both are non-polar but when mixed with each other, they equally disperse into one another until the reaction is completed. Kerosene did not dissolve sodium chloride because Kerosene is non-polar while sodium chloride is polar as dispersion forces happen between two non-polars. The kind of intermolecular force that occurs between polar and non-polar is either ion-induced dipole, or dipole-induced dipole dispersion force. Solute 𝐶2 𝐻6 𝑂(Ethyl Alcohol) Coconut Oil
𝐻2 𝑂
Kerosene
Miscible
Immiscible
Immiscible
Miscible
For the second part of the experiment, another set of solutes, but this time, they are both liquids. The solutes are ethyl alcohol, and coconut oil. The solvents on the other hand are still water and Kerosene. Using the designated droppers for each reagent, 10 drops of coconut oil and 10 drops of ethyl alcohol were put into separate micro test tubes. 20 drops of water were then added to the solutes. After stirring, it can be observed that ethyl alcohol is miscible in water, while coconut oil is not. This was whole process was repeated, but with the use of kerosene as solvent instead of water. The results were as expected; this time coconut oil was the one that is miscible to the solvent, kerosene, while ethyl alcohol was immiscible and behaves like the coconut oil with water.
In the first set of solvents of solutes, it can be explained that the reason why ethyl alcohol is miscible in water while coconut is not, is because water and ethyl alcohol are matching pairs as they are both polar, while coconut oil is a non-polar. A dipole-dipole interaction was immediately present when water was mixed with ethyl alcohol, which is not present between coconut oil and water. Now, with the second setup where kerosene was the solvent, with the results as follows: Coconut oil was miscible in kerosene, while ethyl alcohol is immiscible. The explanation for this is that a dispersion force was present between the two non-polars, wherein the two substances mix with one another uniformly as they behave like polar substances temporarily, just like how kerosene dissolved the naphthalene, but this time, coconut oil is miscible in kerosene. There is an additional part in the experiment and it is about the soft drink. When opened, it released a fizzing sound because of escaping gas. The soft drink’s fizzing sound when opened is explained by Henry’s law. Henry’s law states that the greater the pressure the higher the amount of dissolved gas in a liquid, with that it proves that there is dissolved carbon dioxide in soft drinks which produces the fizzing sound.
Conclusion Based on the results of the experiment, it can be concluded that like dissolves like. A polar substance dissolves in a polar solvent and non-polar substances dissolve in non-polar solvents as the reaction is possible. The reactions are determined whether possible or not if the energy required for the reaction to occur is met or not, meaning they require and consume energy in order to happen. With that logic, the reason why unlike substances don’t mix is because they require more energy than of those which are alike. Also intermolecular forces are involved; polar substances react almost immediately with each other because they have unbalanced charges, while non-polar substances need a dispersion forces. They still finish up the reaction well even though in different ways, but indeed, the like dissolves like. In the soft drink experiment, it can be concluded that the pressure within a system directly relates to the amount of dissolved gas in a solution. Carbon dioxide escaped from the can because of the higher pressure inside it, thus proving that Henry’s Law is correct.