4.1.3 Alkenes

Question 1

are alkenes saturated or unsaturated

Answer 1

unsaturated

Question 2

general formula of an alkene

Answer 2

CnH2n

Question 3

what is the shape and bond angle of an alkene

Answer 3

trigonal planar, 120

Question 4

what are the two distinct bonds in alkenes

Answer 4

pi bonds and sigma bonds

Question 5

which bonds are weaker

Answer 5

pi bonds

Question 6

structural isomerism

Answer 6

have the same molecular formula but a different structural formula

Question 7

stereoisomerism

Answer 7

compounds with the same structural formula but with different arrangements of atoms in space

Question 8

E/Z isomerism

Answer 8

arises from having 2 different groups on each carbon atom of the of the carbon double bond
and the restricted rotation about the carbon double bond

Question 9

in E/Z isomerism which atoms have the highest priority

Answer 9

the highest priority is the highest atomic number

Question 10

in E/Z isomerism if both priorities are on the same side what is the isomer

Answer 10

Z-isomer

Question 11

in E/Z isomer if the priorities are on opposite sides what is the isomer

Answer 11

E-isomer

Question 12

what isomer is the same as E

Answer 12

trans

Question 13

what isomer is the same at Z

Answer 13

cis

Question 14

What 5 reactions can take place between alkanes

Answer 14

1. Hydrogenation (H2)
2. Halogenation (HX)
3. Halogenation (X2)
4. Hydration (H2O)
5. Addition polymerisation

Question 15

What conditions are required for the addition of hydrogen reaction

Answer 15

Hydrogen H2

Nickel catalyst

Question 16

What is the importance of a hydrogen addition reaction

Answer 16

Bonds become saturated

Used in the manufacturing of margarine

Question 17

What conditions are required for the addition of halogens

Answer 17

Cl2, Br2, I2

Room temp

Question 18

What is the context of the addition of halogens

Answer 18

Addition of bromine test presence of double bonds

Iodine used to test unsaturation in vegetable oils

Question 19

What is the test for alkenes

Answer 19

The decolorisation rising of bromine water

Question 20

What conditions are required for the addition of hydrogen halides

Answer 20

HCL, HBr, HI

Room temp

Question 21

What happens when unsymmetrical alkenes react with hydrogen halides and other unsymmetrical molecules

Answer 21

Two isomeric products are formed

Question 22

What are the conditions needed for addition of steam reaction

Answer 22

H2O
Temp >100c
Phosphoric acid catalyst

Question 23

What is the importance of steam addition reactions

Answer 23

Used in industrial manufacture of alcohols

Question 24

Markovnikoff’s Rule

Answer 24

When a compound HX is added to an unsymmetrical alkene, the hydrogen becomes attached to the carbon with the most hydrogens attached to it already

Question 25

Carbocation

Answer 25

A molecules in which a carbon atoms bears three bonds and a positive charge

Question 26

Major product

Answer 26

Formed from the most stable carbocation intermediate in the mechanism

Question 27

Minor product

Answer 27

Formed from the least stable carbocation intermediate in the mechanism

Question 28

polymers

Answer 28

long chained moleculesmader by the joining of many small chained molecules called monomers

Question 29

what is the problem with plastics

Answer 29

they do not breakdown naturally

Question 30

what are the benefits of processing waste polymers

Answer 30

polymers can be turned into chemicals which can be fed into manufacturing of useful products (alkenes to make new polymers, this is called feedstock) when burned polymers produce energy which can generate electricity

Question 31

what is the environmental danger of CO

Answer 31

it is a poisonous gas

Question 32

what is a solution to the production of CO in incineration

Answer 32

supply more oxygen to ensure complete combustion to CO2

Question 33

what is the environmental danger of HCL

Answer 33

acidic so can cause acid rain which can damage buildings

Question 34

what is a solution to the production of HCL in incineration

Answer 34

removing HCL before released by reacting it with bases (NaOH) to neutralise the acid or bubbling water through it to dissolve the HCL

Question 35

how can chemists create more sustainable degradable plastics

Answer 35

biodegradables can be developed from renewable raw materials (starch) degradation of biodegrables in landfill is due to bacterial activity with soil or air photodegradables decompose in the presence of sunlight polyactic for drinks cups food trays made from sugar cane fibre replacing polystyrene