Laboratory Experiment: Classification And Identification Of Hydrocarbons

Introduction

Hydrocarbon is organic compound that contain only carbon and hydrogen. There are four classes of hydrocarbon which are alkanes, alkenes, alkynes and aromatic CITATION nd18 l 1033 (n. n, Virtual Chembook, n. d. ). Hydrocarbons can be in the form of straight chain, branched chain or cyclic molecules. Carbon can form up to four bond and has tetrahedral geometry CITATION nn18 l 1033 (n. n, Hydrocarbons, n. d. ). Aromatic compound derive their name from many compounds in early days of discovery were grouped because they were oils with fragrant odors CITATION Che16 l 1033 (Chemistry LibreTexts, 2016).

Structure

Physical properties: Clear colorless liquid with characteristic aromatic odor. Sweet, pungent, benzene like odor. Boiling point: 111⁰C and melting point: -95⁰ CITATION nn184 l 1033 (n. n, PubChem, n. d. )2. 0 ObjectiveThe objective of this experiment are to investigate the physical properties, solubility and density of an alkane, an alkene and an aromatic compound. This experiment objective was to compare the chemical reactivity of an alkane, an alkene and an aromatic compound and this experiment aim to identify unknown liquids using their physical and chemical properties.

Materials and chemicals

Materials that are needed are: -1% of Bromine (Br2) in cyclohexane1% Iron(III) Chloride FeCl3Petroleum Benzine, Pentenem, Hexane, Toluene.

Combustion

For the combustion part, the instructor will demonstrate the test first. But this part will be conducted at the end after the four of the test listed below was done and try to identify which the two hydrocarbon which will undergoes combustion while doing the four identifying in term of solubility and density of hydrocarbon with water and petroleum benzene, hydrocarbon test with bromine and hydrocarbon test with Iron(III) chloride.

Solubility and Density of Hydrocarbon

Next, for the solubility and density of hydrocarbon first part. First, take six (6) test tubes and label each test tube with names such as Unknown A, Unknown B, Unknown C, Phenol, Hexane and Toluene. Then, for each of the test tube, drop 5 drops of hydrocarbon according to name label on test tube. Then, add 5 drops of water into each test tube. Next, gently mix the test tube then allow the solution to settle down and record the observation. Make sure to save the solution for comparison for the second part of observation. Next for the solubility and density of hydrocarbon second part. First, take another six (6) test tube and label with name like Unknown A, Unknown B, Unknown C, Phenol, Hexane and Toluene. Then, drop 5 drops (can add more if needed) of petroleum Benzine into each test tube. Next, gently mix the solution and allow the solution to settle down. Make sure to record the observation and write on the Table 1. Lastly, throw away all the solution into waste bottle provided inside the fume hood and make sure don’t throw the solution in the sink. Then wash all test tube and put back into test tube racks.

Reaction with Bromine

Firstly, label six (6) test tube with name such as like Unknown A, Unknown B, Unknown C, Phenol, Hexane and Toluene. And then, drop 5 drops of appropriate hydrocarbon according to their name label on test tube. Then, add few drops of bromine water and keep adding and make sure to count the number of drops until the color of Bromine remain unchanged. For the number of drops of bromine, make sure do not drop more than 10 drops (3-4 drops) and if changes can be seen stop dropping any bromine solution. Next, record the observation in Table 2. Lastly, throw all the solution into waste bottle provided inside the fume hood and make sure don’t throw the solution in the sink. Then wash all test tube and put back into test tube racks for next experiment.

Reaction with Iron(iii) Chloride

Firstly, label six (6) test tube with name such as like Unknown A, Unknown B, Unknown C, Phenol, Hexane and Toluene. And then, drop 5 drops of appropriate hydrocarbon according to their name label on test tube. Then, add few drops of 1%Iron(III) Chloride. After that shake to make sure the solution was mixed. Then, keep adding the 1% Iron(llI) Chloride and drop 3-4 drops then record observation that can be observe in Table 2. Lastly, throw all the solution into waste bottle provided inside the fume hood and make sure don’t throw the solution in the sink. Then wash all test tube and put back into test tube racks for drying the test tube.

Results and discussion

For the density test with water and hydrocarbon, most of hydrocarbon was less than the water. The hydrocarbon that had less density than the water was hexane, toluene, unknown A and unknown C. while for phenol and unknown B was denser compared with water. For the colors, it can be observed that all hydrocarbon with water will had colorless and some of the hydrocarbon will make layer and few will be dissolved based on figure 1 above. When doing the experiment, adding more water can make a clear observation on the density with hydrocarbon. Reaction: Phenol + H2Oright32956500 All of the hydrocarbon will form layers and from figure 2 can be observe that all hydrocarbon with the petroleum benzene will form colorless color. For this part, more than 5 drops of petroleum benzine can be drops because when doing the experiment before, we can’t identify which one was dense between hydrocarbons and petroleum benzene.

Phenol and unknown B will form colorless color while the other hydrocarbon such as hexane, toluene, unknown A and unknown C form light brown color. Base on the result, unknown B can be related with the result of phenol which both form colorless color. While for unknown A and unknown B can’t be identify yet because it gave the same light brown color which will be discuss on combustion part for testing. Reactions left29781500Phenol + Br2

Based on table 2 and figure 4 shows the result can be observed in term of the color when hydrocarbon mixed with Iron(III) chloride. In the test with Iron (III) chloride with hydrocarbons, two different color can be observed which are dark purple and light yellow color. Phenol and unknown B formed dark purple in color. While hexane, toluene, unknown A and unknown B formed light yellow color. Based in the color result, it can be confirmed again that compound B was phenol. While compound A and compound C can’t be identifying yet because both of this compound still give the same result which was light yellow color. Reactions: left19494500C6H5OH + FeCl3 right000

To identify which one was hexane and toluene on compound A or Compound C, we need to test it with the flame to undergoes combustion process. Combustion will form carbon dioxide gas. Based on figure 5 above shows that compound C was hexane because it gave a clean small white bowl without any black soot can be observed when heated with flame or fire with lighter. While compound A can be identifying as toluene because both of the small white bowl can be observed with black soot were present on the white bowl when heat with lighter by referring to figure 6. While doing the experiment, some of the hydrocarbon gave medicinal smell like medicine but don’t know which compound had produce medicine smell while washing the test tube.

Conclusion

To conclude, compound A, compound B and compound C can be identifying at the end of the experiment which compound A was toluene, compound B was phenol and compound C was hexane. Based on the result on discussion part, most of the hydrocarbon was not soluble in both water and petroleum benzine. While test with bromine and Iron(III) chloride, color can be observed which in bromine form two which was colorless and light brown and Iron(III) chloride also form two different color which are dark purple color and light yellow color.