Organic Chemistry

Question 1

What happens to a hydrocarbon as the carbon chain becomes shorter?

Answer 1

It becomes less viscous, more volatile, more flammable.

Question 2

What are the first 4 alkanes?

Answer 2

Methane, Ethane, Propane, Butane.

Question 3

What is cracking?

Answer 3

The process of splitting up long-chain hydrocarbons into short-chain hydrocarbons.

Question 4

Describe the process of catalytic cracking.

Answer 4

The long-chain hydrocarbons are heated and consequently vaporised (turned into gas). The vapour is then passed over a hot powdered aluminium oxide catalyst. The long-chain hydrocarbon molecules split apart on the surface of the specks of catalyst .

Question 5

Describe the process of steam cracking.

Answer 5

The long-chain hydrocarbons are heated and consequently vaporised (turned into gas). The vapour is then mixed with steam and then heated to a very high temperature.

Question 6

What is meant when describing an alkane as being ‘saturated’?

Answer 6

Containing the greatest possible number of hydrogen atoms, without carbon–carbon double or triple bonds.

Question 7

Why do alkenes burn with a smoky flame?

Answer 7

There isn’t enough oxygen in the air for complete combustion with alkenes as alkenes need a large amount of oxygen to undergo complete combustion. Because of this, carbon monoxide is produced as well as carbon dioxide and water. Incomplete combustion results in a smoky yellow flame, and less energy being released compared to complete combustion of the same compound.

Question 8

What is a functional group?

Answer 8

A group of atoms in a molecule that determines how that molecule typically reacts (e.g. C=C in alkenes).

Question 9

How do alkenes usually react?

Answer 9

Via addition reactions, the carbon-carbon double bond will open up to leave a single bond and a new atom is added to each carbon.

Question 10

How can a alkane be formed from an alkene?

Answer 10

By hydrogenation. The alkene is reacted with hydrogen in the presence of a catalyst to form an alkane.

Question 11

How can a alcohol be formed from an alkene?

Answer 11

When alkenes react with steam, water is added across the double bond and an alcohol is formed.

Question 12

Alkenes can react with halogens in addition reactions.

TRUE or FALSE?

Answer 12

True

Question 13

How can the addition of a halogen (bromine) to a double bond be used to test for alkenes.

Answer 13

If bromine water is added to an alkene, the bromine will add across the double bond, making a colourless dibromo-compound - so the bromine water is decolourised.

Question 14

What is addition polymerisation?

Answer 14

The process in which unsaturated monomer molecules (alkenes) open up their double bonds and join together to form polymer chains.

Question 15

How can alcohols form carboxylic acids?

Answer 15

Alcohols can be oxidised by reacting with oxygen to produce a carboxylic acid.

Question 16

Why are alcohols used as solvents?

Answer 16

They can dissolve most things water can dissolve, but they can also dissolve substances that water can’t dissolve (e.g. hydrocarbons).

Question 17

Why is ethanol used as a fuel?

Answer 17

It burns fairly cleanly and it’s non-smelly.

Question 18

What method can be used to make ethanol?

Answer 18

Fermentation - an enzyme in yeast is used to convert sugars into ethanol. Carbon dioxide is also produced.

Question 19

What are the best conditions for fermentation?

Answer 19

A temperature of about 37°C, in a slightly acidic solution and under anaerobic conditions (no oxygen).

A reaction between an alkene and steam.

Question 20

What is the functional group of the carboxylic acid homologous series of compounds?

Answer 20

-COOH

Question 21

What are the first 4 carboxylic acids?

Answer 21

Methanoic, ethanoic, propanoic and butanoic acid.

Question 22

What are the first 4 alkenes?

Answer 22

Ethene, propene, butene, pentene.

Question 23

What are the first 4 alcohols?

Answer 23

Methanol, ethanol, propanol, butanol.

Question 24

What can be formed using a carboxylic acid and an alcohol?

Answer 24

Esters are formed from an alcohol and a carboxylic acid in the presence of a acid catalyst.

Question 25

What is an example of an ester?

Answer 25

Ethyl ethanoate

Question 26

What is condensation polymerisation?

Answer 26

Condensation polymerisation involves monomers which contain different functional groups. The monomers react together and bonds form between them, making polymer chains. For each new bond that forms, a small molecule (e.g. water) is lost.

Question 27

What are naturally occurring polymers?

Answer 27

Proteins (polymers of amino acids), DNA molecules (monomers called nucleotides) and carbohydrate polymers (sugars)