Alkanes

Question 1

homologous series def

Answer 1

a group of compounds with the same general formula and same functional group, so they have similar chemical reactions. each successive member differs by a CH2 group, so there is gradual change in physical properties

Question 2

hydrocarbon def

Answer 2

a compound containing only hydrogen and carbon

Question 3

saturated (in organic chemistry) def.

Answer 3

contains all single bonds, so has maximum number of hydrogen atoms

Question 4

unsaturated (in organic chemistry) def

Answer 4

does not contain all single bond e.g contains a double carbon-carbon bond

Question 5

isomers def

Answer 5

molecules with same molecular formula but different structural formulae

Question 6

functional group def

Answer 6

A group of atoms bonded in a specific arrangement that influences the properties of the homologous series

Question 7

substitution reaction

Answer 7

• occurs in alkanes (e.g when reacting with halogens)
• is when two functional groups replace one another
• e.g bromine and an alkane substitute one another when left to react under UV light (bromine goes colourless)

Question 8

addition reaction

Answer 8

• occurs in alkenes (e.g when they react with halogens)
• is when two functional groups add together to form 1 product
• e.g bromine and alkene react together (UV light not needed) and bromine is decolourised

Question 9

combustion in organic chemistry

Answer 9

• occurs in alcohols, alkanes and alkenes, in the same way:
• forms carbon dioxide and water (when there is an unlimited supply of air/oxygen (compete combustion)- if not, then carbon monoxide is formed instead of CO2 (incomplete combustion))

Question 10

physical properties of alkanes

Answer 10

• colourless

- gradual change in properties as number of carbon atoms increase

Question 11

oxidising ethanol through combustion

Answer 11

• forms carbon dioxide and water

- ethanol is burnt in presence of air

Question 12

oxidising ethanol through microbial oxidation

Answer 12

• alcohol reacts with air and bacteria in the air to form a carboxylic acid
• ethanol + oxygen → ethanoic acid + water

Question 13

oxidising ethanol through heating with an oxidising agent

Answer 13

• oxidising agent is potassium dichromate (VI), and is heated with dilute sulphuric acid
• ethanol oxidises to ethanoic acid
• potassium dichromate turns from orange to green

Question 14

ways of manufacturing on ethanol

Answer 14

1. By hydration of ethene

2. by fermentation of glucose

Question 15

advantages and disadvantages of manufacturing of ethanol through fermentation

Answer 15

ADVANTAGES
- sugar can be grown so is renewable
- uses less energy
DISADVANTAGES
- slow, batch process
- only 15% ethanol produced (this is the concentration at which the yeast is killed off)

Question 16

advantages and disadvantages of producing ethanol through hydration

Answer 16

ADVANTAGES
- fast process
- continuous process
- 100% ethanol produced
DISADVANTAGES
- ethene comes from crude oil and so isn't renewable
- high energy needed