Organic Chemistry

Question 1

What is a functional group?

Answer 1

Is an atom or a group of atoms within a molecule that shows a characteristic set of physical and chemical behaviours.
OR
a group of atoms responsible for the characteristic reactions of a particular compound.

Question 2

State 3 importance of functional groups.

Answer 2

1. They take part in chemical reactions.
2. They determine the physical properties of the molecule.
3. They help in classifying and naming organic compounds.

Question 3

What are hydrocarbons?

Answer 3

Are organic compounds that contain carbon and hydrogen atoms which are joined by covalent bonds.

Question 4

Define the term ‘Homologous Series’.

Answer 4

Is a series of compounds with the same general formula, functional group and have similar chemical reactions..

Question 5

Name the two groups hydrocarbons are divided into?

Answer 5

Saturated and unsaturated.

Question 6

Define saturated hydrocarbon.

Answer 6

Hydrocarbons that contain carbon- carbon single bonds. Alkanes are saturated hydrocarbons.

Question 7

Define unsaturated hydrocarbons

Answer 7

Are hydrocarbons that contain one or more carbon-carbon double bonds or triple bonds. Alkenes and Alkynes are unsaturated hydrocarbons.

Question 8

What is the molecular formula of the hydrocarbon group Alkane?

Answer 8

CnH2n+2

Question 9

Why do Alkanes form homologous series?

Answer 9

because each successive member differs from the next by a group of CH2.

Question 10

What are substituent groups?

Answer 10

Are the side branches in organic compounds.

Question 11

List 3 ways structural formulas of organic compounds can be represented?

Answer 11

1. Expanded
2. Condensed
3. Line-angle formula

Question 12

State some physical properties of alkanes.

Answer 12

1. They are non-polar compounds.
2. The are insoluble in water as water in polar. They are soluble in non-polar solvents.
3. Have lower density than water. Lower than 1.0gm/L.
   4.As the number of carbons increases, the melting and boiling points increase as well.

Question 13

What is a chemical property of alkanes.

Answer 13

They have a low reactivity.

Question 14

The most important reactions in alkanes are?

Answer 14

Combustion and substitution reaction.

Question 15

What reaction does alkane have on litmus paper?

Answer 15

neutral to litmus paper.

Question 16

What is the observation of completely reacting alkanes with oxygen( complete combustion)?

Answer 16

Blue non smoky flame.

Question 17

What is the observation of incompletely reacting alkanes with oxygen (incomplete combustion)?

Answer 17

Sooty flame.

Question 18

How do you test for alkene?

Answer 18

They turn the bromine water colorless.

Question 19

What are the products of combustion reaction?

Answer 19

*CO2 and H2O- complete combustion.
*CO2 and H2O or CO and H2O- incomplete combustion.

Question 20

which catalyst is used in the halogen substitution reaction of alkanes?

Answer 20

Sunlight or UV light.

Question 21

State 2 ways ethene gas can be produced?

Answer 21

1. Steam cracking of alkanes.
2. Dehydration of ethanol

Question 22

Explain the process of steam cracking.

Answer 22

A process in which saturated hydrocarbons are broken down into smaller, often unsaturated hydrocarbons.

Question 23

Give an example equation of steam cracking of alkanes.

Answer 23

C11H24 —- C9H20 + C2H4
reacts with steam at 900 degrees Celsius..

Question 24

Explain the process of dehydration of ethanol.

Answer 24

Ethanol is dehydrated to produce ethene and water when heated with concentrated sulfuric acid (H2SO4).

Question 25

What is the function of sulfuric acid in dehydration of ethanol.

Answer 25

It acts as a catalyst.

Question 26

State the reaction equation of dehydration of ethanol.

Answer 26

• CH3CH2OH ——- C2H4 + H2O
  reacting with sulfuric acid as a catalyst.

Question 27

What happens in a substitution reaction?

Answer 27

A single hydrogen is replaced by a halogen such as bromine and chlorine.

Question 28

State the general formula of alkynes.

Answer 28

CnH2n-2

Question 29

Explain how ethyne gas can be prepared.

Answer 29

By the reaction of water with calcium carbide (CaC2).

Question 30

Comment on the physical appearance of ethyne and ethene gas.

Answer 30

It is a colorless gas.

Question 31

State the reaction equation of the ethyne gas.

Answer 31

CaC2 + H2O —— C2H2 + Ca(OH)

Question 32

State a chemical property of alkynes.

Answer 32

More reactive than alkanes as they contain one or more carbon carbon triple bonds.

Question 33

What is the most characteristic reaction of alkenes and alkynes?

Answer 33

Addition to the carbon to carbon double or triple bond.

Question 34

Explain what happens in the hydration addition reaction.

Answer 34

There is addition of water molecules to alkenes to form alocohols.

Question 35

What catalyst’s is used in the hydration reaction of ethene.

Answer 35

Phosphoric acid (H3PO4) and silica.

Question 36

What happens in a halogenation reaction?

Answer 36

There is addition of halogens such as bromine and chlorine to alkene and alkynes.

Question 37

What happens in a hydrohalogenation reaction?

Answer 37

There is addition of molecules such as HBr, HCl, HF, HI.

Question 38

What happens in a hydrogenation reaction?

Answer 38

There is addition of hydrogen atoms to carbons in double and triple bonds to form alkanes.

Question 39

What are the catalysts used in hydrogenation reactions?

Answer 39

*Platinum (Pt)
*Nickel (Ni)

Question 40

Explain how you would test for the presence of unsaturation.

Answer 40

When alkene and alkyne are bubbled through bromine water, its presence decolorizes the bromine water. The disappearance if the red colour as bromine is added to the double and triple bond, indicates the presence of unsaturation.