Question

1.Considering your results in the solubility tests, what do you conclude about the solubility of hydrocarbons in water? Predict the solubility of gasoline and motor oil in water.

2.Are hydrocarbons less dense or more dense than water? Does this have any practical importance when oil spills occur?

3.Write equations using 1-butene to illustrate the reactions occurring in Test D, E, and F of the experimental procedure (use your text).

4.Write equations using cyclohexene to illustrate the reactions in Tests D, E and F.

5.Write a balanced equation for the complete combustion of octane. What other product(s) are produced when incomplete combustion of octanes occurs in an automobile engine?

6.How could one distinguish octane from 1-octane from 1-octene by a simple chemical test; 1-octanol from 1-octene; and toluene from 1-octene?

Answer 1

1. Hydrocarbons do not dissolve in water because they are nonpolar compounds and water is a polar solvent. The general solubility rule is like dissolves like. All hydrocarbons are nonpolar, so they are insoluble in water. Gasoline and motor oil both are hydrocarbon, so they will not dissolve in water.

2. Hydrocarbons are less dense than water; so they float on the surface. This knowledge can be used in the context of oil spills because the slick will be on the surface and can be skimmed off.

3. Write equations using 1-butene to illustrate the reactions occurring in Test D-

CH₂ =CHCH₂CH₃ + Br₂ --------.> CH₂ (Br) CH (Br) CH₂ CH₃

Bromine is decolorized (unsaturation test)

Test E-

1-butene is reacted with dilute alkaline aqueous KMnO4 solution to produce 1, 2-Butanediol .KMnO₄ is decolorized.

CH₂ =CHCH₂CH₃ + KMnO₄ ------> CH₂ (OH) CH (OH) CH₂ CH₃ + MnO₂

TestF-

CH2 =CHCH2CH3 + KMnO4 + H₂SO4 = C₂H₅COOH + H2O + MnSO4 + K2SO4

4. Write equations using cyclohexene to illustrate the reactions in Tests D-

C6H12 + Br2 ---> C6H11Br + HBr

(the is a substitution reaction, can only be done when sunlight is present)

Cyclohexene as one of alkenes succumbs the reactions of electrophilic addition, so in reaction with Br₂:

C6H10 + Br2 ---> C6H10Br2 (1,2-dibrom cyclohexane)

Test-E

In reaction with KMnO4, Cyclohexene is oxidized to the alcohol with two hydroxyl groups.

C6H10 + KMnO4 ---> C6H10 (OH)2 (1,2 dihydroxicyclohexane) + MnO2

5. Write a balanced equation for the complete combustion of octane.

2 C8H18 + 25 O2 = 16 CO2 + 18 H2O

Incomplete combustion of octanes occurs in an automobile engine

1) 2 C8H18 + 9 O2 = 16 C + 18 H2O

2) 2 C8H18 + 17 O2 = 16 CO + 18 H2O