Unit 12: Hydrocarbon

What are Hydrocarbons?

Hydrocarbons are the simplest organic compounds, consisting solely of carbon and hydrogen atoms. This unit introduces students to the diverse types of hydrocarbons, their structures, and their significance in both natural and industrial contexts. Hydrocarbons are the primary building blocks of organic chemistry and are found in everything from fossil fuels to biological molecules.

Key Topics in Hydrocarbons:

• Types of Hydrocarbons: Understanding the different categories, including alkanes (saturated hydrocarbons), alkenes (unsaturated hydrocarbons with double bonds), and alkynes (unsaturated hydrocarbons with triple bonds).
• Isomerism in Hydrocarbons: Exploring how hydrocarbons with the same molecular formula can have different structures, leading to various properties.
• Sources of Hydrocarbons: Learning about natural sources such as crude oil, natural gas, and their extraction and refining processes.
• Reactions of Hydrocarbons: Studying key reactions like combustion, substitution, and addition, which are essential in energy production and chemical manufacturing.
• Environmental Impact: Examining the role of hydrocarbons in pollution and climate change, along with sustainable alternatives and practices.

Benefits of Studying Hydrocarbons:

• Understanding Energy Sources: Provides a foundation for comprehending how fossil fuels are processed and used as energy sources.
• Industrial Applications: Equips students with knowledge about the chemical processes involved in creating everyday products from hydrocarbons.
• Environmental Awareness: Raises awareness about the environmental challenges associated with the use of hydrocarbons and the importance of sustainable practices.

This unit is essential for students to grasp the basics of organic chemistry and the pivotal role hydrocarbons play in both industrial processes and the environment. Mastery of hydrocarbons sets the stage for deeper exploration into more complex organic compounds.

1. Which one of these hydrocarbon molecules would have no effect on an aqueous solution of bromine?

a. CH4
b. C10H20
c. C2H4
d. C2H2

2. If an organic compound has 4 carbon atoms, all singly bonded, it will have the following characteristics except one

a. it will be saturated hydrocarbon
b. it will have 8 hydrogen atoms
c. its name will be n-butane
d. it will be least reactive

3. The reduction of alkyl halides takes place in the presence of

a. Zn/HCl
b. Na/HCl
c. Mg/HCl
d. Cu/HCl

4. Halogenation of methane does not produce

a. carbon tetrachlroide
b. chloroform
c. carbon black
d. chloromethane

5. Incomplete combustion of alkanes produces

a. carbon dioxide only
b. carbon monoxide only
c. carbon monoxide and carbon black
d. carbon dioxide and carbon black

6. Alkenes are prepared from alcohols by a process called

a. dehydrogenation
b. dehalogenation
c. dehydration
d. dehydrohalogenation

7. Dehydrohalogenation takes place in the presence of

a. aqueous NaOH
b. alcoholic KOH
c. alcoholic NaOH
d. aqueous KOH

8. Oxidation of ethene with KMnO4 produces

a. oxalic acid
b. glyoxal
c. ethane glycol
d. propene glycol

9. Which one of these is a saturated hydrocarbon

a. C2H4
b. C3H6
c. C4H8
d. C5H12

10. A hydrocarbon has molecular formula C8H14. What is the molecular formula of the next member of the same homologous series?

a. C9H18
b. C9H16
c. C9H20
d. C9H12

11. What is the molecular formula for the eight alkane member octane , that is found in petrol

a. C8H8
b. C8H16
c. C8H18
d. C8H20

12. One of the hydrocarbons reacts with one mole of hydrogen to form a saturated hydrocarbon.What could be the formula of the X.

a. C3H8
b. C6H12
c. C4H10
d. C7H16

13. Dehydration of alcohols can be carried out with

a. NaOH
b. KOH
c. H2SO4
d. HCl

14. The end product of oxidation of acetylene is

a. oxalic acid
b. glycol
c. glyoxal
d. none

15. Dehalogenation of tetrahalides produces acetylene. This reaction takes place in the presence of

a. sodium metal
b. zinc metal
c. magnesium metal
d. potassium metal

16. Substitution reaction is the characteristics of

a. alkanes
b. alkenes
c. alkynes
d. none

17. Halogenation of methane in the presence of diffused sunlight takes place

a. suddenly, only in one step
b. slowly in one step
c. in a series of four steps
d. fastly in two steps

18. Which one of the following is a substitution reaction?

a. halogenation of alkynes
b. halogenation of alkenes
c. halogenation of alkanes
d. bromination of alkenes

19. The order of reactivity of hydrogen halides with alkenes is

a. HI > HBr
b. HBr > HI
c. HCl > HBr
d. HBr < HCl

20. Oxidation of alkenes produces

a. glyoxal
b. glycol
c. oxalic acid
d.formic acid