Organic Chemistry - Part 1 (T3)

Question 0

What are the two most vital elements in the chemical process of life?

Answer 0

• hydrogen - carbon

Question 1

Describe ‘organic chemistry’ in a sentence…

Answer 1

Chemistry that forms the fundamental core of the chemical processes of life

Question 2

What are long chains of hydrogen and carbon atoms called?

Answer 2

Hydrocarbons

Question 3

Briefly, what is a homologous series?

Answer 3

• a family of chemicals that have a series of similar formulas, often giving them similar chemical formulas - the alkanes are the simplest homologous series

Question 4

What is an isomer?

Answer 4

• a chemical that has a similar formula but a different structure of the atoms within the molecules - this is known as isomerism

Question 5

What is a hydrocarbon?

Answer 5

• a companion that contains carbon and hydrogen only - the carbon atoms are joined carbon-carbon single bonds

Question 6

What is the major component of natural gas?

Answer 6

Methane

Question 7

Explain how the molecules of the members of a homologous series increase…

Answer 7

• the molecules of the members of a homologous series increase in size in a regular way - there is always a difference of CH2 between one member and the next - as the molecules get bigger, the intermolecular forces between them increase, meaning more energy has to be put in to break the attractions between one molecule and its neighbours

Question 8

What is one effect of the fact that molecules of the members of a homologous series increase in size in a regular way?

Answer 8

The boiling point also increases in a regular way

Question 9

Explain what is meant by the statement “members of a homologous series have similar chemical properties”

Answer 9

• chemical properties are dependent on boiling - because alkanes only contain carbon-carbon single bonds and carbon-hydrogen bonds, they are all going to behave in the same way - these are strong bonds, and alkanes don’t have a lot of chemical reactions

Question 10

The formation of carbon monoxide from incomplete combustion of hydrocarbons is very dangerous. Explain..

Answer 10

• carbon monoxide is colourless, odourless and very poisonous - it is a danger to humans as it combines with haemoglobin and prevent it from carrying oxygen - as a result, you die or become very ill as not enough oxygen gets to the cells in your body

Question 12

What happens if a mixture of methane and bromine is exposed to sunlight?

Answer 12

• a mixture of methane and bromine gas is brown because of the presence of bromine - if it exposed to sunlight, it loses colour - a mixture of bromomethane and hydrogen bromide gases is formed

Question 13

What mixture is created if a mixture of methane and chlorine is exposed to UV light?

Answer 13

You would get a mixture chloromethane and hydrogen chloride gases

Question 14

Describe a common situation where incomplete combustion is unavoidable and carbon monoxide is produced

Answer 14

For cars to use the energy from burning their hydrocarbons, the combustion has to occur in an enclosed space, meaning that carbon monoxide is produced

Question 15

What is the general formula for alkanes?

Answer 15

Cn H2n+2

Question 16

What is the general formula for alcohol?

Answer 16

Cn H2n+1 OH

Question 17

What is produced if bromine is added to ethene?

Answer 17

• 1,2-dibromoethane is produced - it is a colourless liquid

Question 18

Decode the name ‘1,2-dibromoethane…

Answer 18

• ‘eth’ shows a two-carbon chain - ‘ane’ shows only carbon-carbon single bonds - ‘1,2-dibromo’ shows two bromine atoms attached to the first and second carbon atoms

Question 19

Any compound with a carbon-carbon double bond will react with bromine in a similar way. What would this be used to test?

Answer 19

To test for a carbon-carbon double bond

Question 20

How would you use bromine water to test a compound for a carbon-carbon double bond?

Answer 20

• if you shake an unknown organic compound with bromine water and the orange bromine water is de-colourised, the compound contains a carbon-carbon double bond - if your unknown compound is a gas, simply bubble it through bromine water for the same effect

Question 20

What is the name of the alcohol found in drinks and what is its chemical formula?

Answer 20

• ethanol - C2 H5 OH

Question 21

What is significant to about alcohols, making them stand out from other hydrocarbons?

Answer 21

They all have an -OH group conveniently bonded onto a carbon chain

Question 22

The chemical formula for ethanol is C2 H5 OH but how would we write that if we wanted to be clearer about the construction of the molecule?

Answer 22

CH3 CH2 OH

Question 23

Describe making alcohol by fermentation, focusing on the use of sucrose to start…

Answer 23

• yeast is added to a sugar or starch solution and left in the warm (around 30-40 deg.) for a few days in the absence of air - if starting with a normal sugar such as sucrose, the sucrose is split into two smaller sugars, glucose and fructose - glucose and fructose have the same molecular formulae but different structures (they are isomers) - enzymes in the yeast convert the sugars into ethanol and carbon dioxide

Question 24

How is alcohol purified and why can it not be made through fermentation?

Answer 24

• yeast is killed by more than about 15% of alcohol in the mixture so it is not possible to make pure alcohol through fermentation - alcohol is purified using fractional distillation, taking advantage of the different boiling points of ethanol and water - water boils at 100 degrees and ethanol boils at around 78 degrees - the liquid distilling over at 78 degrees is 96% pure ethanol with 4% water. It is not possible to remove this 4% water through fermentation

Question 25

Describe the process of making ethanol by the hydration of ethene…

Answer 25

• ethanol is also made by reacting ethene with steam, through a process called hydration - this is carried out at very high pressure (around 60-70 atmospheres) and temperature (300 degrees C) - the catalyst is phosphoric acid - only a small proportion of the ethene reacts. The ethanol produced is condensed as a liquid and the unreacted ethene is recycled through the process

Question 26

What are the differences in the use of resources between the two methods of producing ethanol?

Answer 26

Fermentation - uses renewable resources such as sugar beet or sugar cane, corn and other starchy materials Hydration of ethene - use finite resources and once all the oil is used up there won’t be any more

Question 27

Compare the ‘type of process’ with the two methods of producing ethanol…

Answer 27

Fermentation - a batch process - everything is mixed together in a reaction vessel and then left for several days - that batch is then removed and a new reaction is set up - this is inefficient Hydration of ethene - a continuous flow process - a stream of reactants is constantly passed over the catalyst - much more efficient than a batch process

Question 28

Compare the rates of reaction in the two process for making ethanol..

Answer 28

Fermentation - slow, taking several days for each batch Hydration of ethene - rapid

Question 29

Compare the quality of product with the two processes of making ethanol..

Answer 29

Fermentation - produces very impure ethanol that requires further processing Hydration of ethene - produces much purer ethanol

Question 30

Compare the reaction conditions between fermentation and hydration of ethene to make ethanol..

Answer 30

Fermentation - uses gentle temperatures and ordinary pressure Hydration of ethene - uses high temperatures and pressures, needing a high input of energy

Question 31

Ethanol is a biofuel. What does that mean?

Answer 31

• a biofuel is a fuel made from biological sources, such as sugar cane or maize - mixtures of ethanol and petrol are becoming increasingly popular in countries like Brazil who have little or no means of producing their own petrol - other countries are introducing biofuels such as ethanol to reduce dependence on fossil fuels such as oil and gas

Question 32

What is the process of ‘dehydrating alcohols’?

Answer 32

• dehydration refers to the removal of water from a compound - the dehydration of ethanol produces ethene - ethanol vapour is pass over hot aluminium oxide acting as a catalyst