organic chemistry ⚗

Question 1

what are hydrocarbons?

Answer 1

compound which contain only carbon and hydrogen

Question 2

what are organic compounds?

Answer 2

compounds which contain carbon, hydrogen, oxygen…

Question 3

what is a homologous series?

Answer 3

a family of organic compounds with the same functional group and similar chemical properties. they have the same general formula and successive members differ by a -CH2- group

Question 4

trends of physical properties down a homologous series

Answer 4

1) melting and boiling points increases down the series
2) viscosity of liquid increases down the series
3) flammability decreases down the series and they burn with a more sooty flame

Question 5

why do melting and boiling points increase down the series?

Answer 5

down the group, relative molecular mass increases and more energy is required to overcome the stronger intermolecular forces of attraction between larger molecules, hence melting and boiling points increase

Question 6

why does viscosity increase down the series?

Answer 6

down the series, liquid flows less easily due to stronger electrostatic forces of attraction between larger molecules, hence viscosity increases

Question 7

why do compounds burn with a more sooty flame down the series?

Answer 7

the percentage of carbon content in the compound increases down the group, hence the compound burns with a more sooty flame

Question 8

order of fractional distillation of petroleum

Answer 8

1) petroleum gas
2) petrol
3) naphtha
4) kerosene
5) diesel
6) lubricating oil
7) bitumen

Question 9

use of petroleum gas

Answer 9

cooking

Question 10

use of petrol

Answer 10

fuel for car engines

Question 11

use of naphtha

Answer 11

feedstock for the petrochemical industry

Question 12

use of kerosene

Answer 12

fuel for aircraft engines, cooking using oil stoves

Question 13

use of diesel

Answer 13

fuel for diesel engines

Question 14

use of lubricating oil

Answer 14

making waxes and polishes

Question 15

use of bitumen

Answer 15

for paving road surfaces

Question 16

what is catalytic cracking and its conditions?

Answer 16

the process of breaking down long-chain hydrocarbons into shorter chain hydrocarbons by passing the hot vapourised hydrocarbons over a heated catalyst
- aluminium oxide and silicon oxide as catalysts at 600°C

Question 17

what is the importance of cracking?

Answer 17

converts long-chain hydrocarbons high in supply low in demand to shorter-chain hydrocarbons high in demand but low in supply

Question 18

alkanes general formula and functional group

Answer 18

CnH2n+2, no functional group

Question 19

define isomer

Answer 19

molecules with same molecular formula but different structural formula

Question 20

chemical reactions of alkanes

Answer 20

1) combustion
2) substitution reaction: direct replacement of hydrogen with a halogen one atom by one atom (in presence of ultraviolet light)

Question 21

alkenes general formula and functional group

Answer 21

CnH2n, C=C functional group

Question 22

chemical reactions of alkenes

Answer 22

1) combustion
2) addition of hydrogen (hydrogenation)
- addition of hydrogen across C=C to form alkanes; 180°C, nickel as a catalyst
3) addition of bromine
- orange aqueous bromine decolourises rapidly; presence of ultraviolet light
4) addition of steam (hydration)
- addition of steam across C=C to form alcohols; 300°C, 65atm, phosphoric acid as a catalyst
5) addition polymerisation
- open up the C=C bonds; high temperature and pressure, presence of catalyst

Question 23

similarities between alkanes and alkenes

Answer 23

• both are hydrocarbons
• both undergo combustion reactions

Question 24

differences between alkanes and alkenes

Answer 24

• alkenes are unsaturated, alkanes are saturated
• alkenes reactive, alkanes unreactive
• alkenes burn with a more sooty flame
• all the alkene reactions

Question 25

alcohols general formula and functional group

Answer 25

general formula CnH2n+1OH, functional group hydroxyl group -OH

Question 26

chemical reactions of alcohols

Answer 26

1) combustion
2) oxidation
- alcohols oxidised to form carboxylic acids, by atmospheric oxygen or oxidising agents; heat with oxidising agents
3) dehydration
- water is removed to form alkenes; 170°C with concentrated sulfuric acid as a dehydrating agent

Question 27

manufacture of alcohols

Answer 27

1) hydration of alkenes
2) fermentation of glucose
- yeast, absence of oxygen, best at 37°C

Question 28

carboxylic acids general formula and functional group

Answer 28

general formula CnH2n+1COOH where n = 0,1.., functional group carboxyl group -COOH

Question 29

chemical reactions of carboxylic acids

Answer 29

1) all acid reactions: metal, metal carbonate, alkalis/bases
2) esterification
- reaction with alcohols to form esters with the removal of water; heat under reflux with concentrated sulfuric acid as a catalyst

Question 30

what is the name of CH3CH2CH2COOCH3?

Answer 30

methyl butanoate

Question 31

process of condensation polymerisation

Answer 31

monomers join together to form a polymer with the removal of water

Question 32

peptide linkage

Answer 32

O=C-N-H

Question 33

ester linkage

Answer 33

O=C-O

Question 34

differences between addition and condensation polymerisation

Answer 34

• addition have unsaturated monomers, condensation have monomers with two functional groups (di-)
• addition polymer has the same empirical formula as monomer, condensation doesn’t
• addition no side products produced, condensation water produced