Alkenes

Question 1

Alkenes are what kind of hydrocarbons

Answer 1

Unsaturated hydrocarbons

Question 2

Alkenes have the general formula

Answer 2

CnH2n

Question 3

Unsaturated hydrocarbons are ………

Hybridized

Answer 3

Sp2

Question 4

Pyrolysis means…..

Answer 4

Burning by fire

Question 5

In the industrial preparation of alkenes what condition is required

Answer 5

Cracking/Pyrolysis

Question 6

In the dehydration of ethanol conc sulphuric acid play what role

Answer 6

It plays the role of a dehydrating agent as well as a catalyst.

Question 7

What is the condition in dehydrohalogenation of haloalkanes for the preparation of alkene

Answer 7

Heat and alcoholic potassium hydroxide(KOH)

Question 8

Dehydrohalogenation proceeds more easily in

Answer 8

Secondary and tertiary haloalkanes

Question 9

Condition necessary for the partial reduction of alkyne for the preparation of alkenes……

Answer 9

Hydrogen in the presence of Lindlar agent.

Question 10

What are the products in the industrial method of preparation of alkenes

Answer 10

Alkene and hydrogen

Question 11

Tetrachloromethane is also known as

Answer 11

Carbon tetrachloride (CCL4)

Question 12

Tests for unsaturation are…..

Answer 12

Hydroxylation
Addition of Bromine water
Addition of Halogens

Question 13

What is polymerization?

Answer 13

Polymerization is the process by which small molecules/monomers join together to form very large molecules/macromolecules/polymers.

Question 14

List the synthetic preparations of alkenes

Answer 14

Partial reduction alkynes
Dehydrohalogenation of haloalkanes
Dehydration of ethanol

Question 15

List the synthetic preparations of Alkanes

Answer 15

Hydrogenation of Alkenes
Reduction of Haloalkanes
From Grignard reagent(RMgX- Alkyl- Magnesium halide)
Kolbe’ synthesis
Wurtz synthesis

Question 16

What type of bonds does alkenes have

Answer 16

1 pi-bond
1 sigma-bond

Question 17

In dehydration of ethanol, for the synthetic preparation of alkene, what temperature and catalyst is required

Answer 17

Conc H²SO⁴
170°C

Question 18

What is the reactant in the industrial preparation of an alkene?

Answer 18

Petroleum

Question 19

Alkenes are takes place at low temperature. True or false.

Answer 19

Alkenes takes place at high temperature, therefore its endothermic.

Question 20

Which of the following is not colourless.
Butene
Ethene
Propene
Methene

Answer 20

Ethane, because due to the lack of C-C bond.

Question 21

Baeyer’s reagent is used to detect

Answer 21

Double-bonds

Question 22

Cis-isomerism in alkenes is due to

Answer 22

Restricted rotation around the double bond

Question 23

Which of the following reactions is common in alkenes:
Addition
Elimination
Substitution
Superposition

Answer 23

Addition reaction

Question 24

Ethylene bromide on treatment with Zn gives

Answer 24

Alkene

Question 25

Another name for an alkene is.....

Answer 25

Olefin

Question 26

For chemical industry the most important alkenes are

Answer 26

Propene, ethene, 1,3-butadiene

Question 27

What is the solubility of alkenes

Answer 27

Alkenes are less soluble in water due to weak van-waal forces.

Question 28

Are alkenes acidic or basic

Answer 28

Alkenes are weak bases because the Pi electrons are only avaliable after breaking the pi-bond fordt6

Question 29

Why are alkenes more reactive than alkanes

Answer 29

Due to the relative instability of the double bond

Question 30

How do u test for Alkene

Answer 30

Use Bromine water. There is no change when Bromine water is mixed with alkane, but it turns colourless when mixed with alkene.

Question 31

What are the applications of alkenes

Answer 31

Used in the synthesis of alcohol,plastic, detergent, lacquers and fuel as starting material

Question 32

How do you identify a double bond in an alkene

Answer 32

Bromine water can be used to identify the position of a double bond. In this reaction, the red-brown colour of Bromine turns into colourless, indicating that there is a double bond.

Question 33

What are the main sources of alkenes

Answer 33

Oil and natural gas

Question 34

What is the oxidising agent of alkene

Answer 34

Osmium tetroxide (OsO⁴)

Question 35

What is the name of an alkene with oxygen

Answer 35

Epoxides