Question 4There are 2 unlabeled bottles of chemicals in laboratory in which one of the bottles is pentane and the other one is pentene. Suggest three chemical tests that can help you to determine which of the two bottles is alkane and alkene. (10 marks)PentaneTest 1Pentanes are relatively inexpensive and are the most volatile alkanes that are liquid at room temperature, so they are often used in the laboratory assolvents that can be conveniently evaporated.Theboiling pointsof the pentane isomers range from about 9 to 36 C. As is the case for other alkanes, the more branched isomers tend to have lower boiling points.Test 2However, because of theirnonpolarity and lack offunctionality, they can only dissolve non-polar and alkyl-rich compounds.The same trend normally holds for themelting pointsof alkane isomers, and indeed that of isopentane is 30 C lower than that ofn-pentane. However, the melting point of neopentane, the most heavily branched of the three, is 100 C higherthat of isopentane. The anomalously high melting point of neopentane has been attributed to the better solid-state packing assumed to be possible with its tetrahedral molecule; but this explanation has been challenged on account of it having a lower density than the other two isomers.Test 3Pentanes aremisciblewith most common nonpolar solvents such aschlorocarbons,aromatics, andethers. They are also often used inliquid chromatography.The branched isomers are more stable (have lowerheat of formationandheat of combustion) than normal pentane. The difference is 1.8 kcal/mol for isopentane, and 5 kcal/mol for neopentanePenteneTest 1Pentenerefers to all thealkeneswithchemical formulaC5H10.There are a total of six different compounds in this class, differing from each other by whether the carbon atoms are attached linearly or in a branched structure, and whether the double bond has acisortransform.

Test 2Pentene is analpha-olefin. Most often 1-pentene is made as a byproduct ofcatalyticorthermal crackingofpetroleum, or during production ofethyleneandpropylenevia thermal cracking of hydrocarbon fractions. It is rarely isolated as a separate compound. Instead, it is most often blended intogasolineor, in a mixture with other hydrocarbons,alkylatedwithisobutaneto make gasoline.Test 3Properties

Molecular formula C5H10

Molar mass 70.13 g mol1

Density 0.64 g/cm3(1-pentene)

Melting point -165.2 C (1-pentene)

Boiling point 30 C (1-pentene)