Organic Chemistry

Question 1

Describe crude oil:

Answer 1

Found in rocks
finite resource.
formed over millions of years from remains of plankton.

Mixture of hydrocarbons

Question 2

High viscosity:

Answer 2

Flow slowly

Question 3

Properties of hydrocarbons

Answer 3

As the size of the hydrocarbon molecule increases, becomes more viscous.
Short chain hydrocarbons are extremely flammable (can be sued as fuels).
Long chain hydrocarbons have very high boiling points and vice versa.

Question 4

Fractional distillation

Answer 4

Crude oil is heated to a very high temperature.
Causes it to boil and evaporate into a gas.
Crude oil is now fed into the distillation column.
The vapours now rise up the column.
Column is hotter at the bottom and cooler at the top.
Hydrocarbons condense when they reach their boiling point.
The liquid fractions are then removed.
The remainiong hydrocarbons rise up the column and condense when they reach their boiling point.
Very long chain hydrocarbons have very high boiling points so they are removed at the bottom of the column as liquids.
Very short chain hydrocarbons have very low boiling points so they don’t condense and they leave at the top of the column as gases,

Question 5

What are the uses of fractions in the crude oil.

Answer 5

Fuels:
Petrol and diesel
Kerosene
Heavy fuel oil.
Liquified petroleum gas.

Feedstock in the petrochemical industry:
This is a chemical that is used to make other chemicals.

Question 6

What is cracking?

Answer 6

A long chain alkane is broken down into a smaller chain hydrocarbon.
These can be used as fuels since they are more flammable.

Question 7

What conditions are needed for cracking?

Answer 7

Catalytic cracking:
High temperature and a catalyst.

Steam cracking:
High temperature and steam.

Question 8

Why are alkenes useful?

Answer 8

They can make polymers.
Used as the starting material for other useful chemicals as well.
More reactive than alkanes.

Question 9

Testing for alkenes

Answer 9

Shake the alkene with bromine water.

Turns colourless.

Question 10

Why are alkenes unsaturated?

Answer 10

They have two fewer hydrogen atoms than the alkane with the same number of carbon atoms.

Question 11

Why do all alkenes react in a similar way?

Answer 11

Because the contain a double bond.

Question 12

What is meant by the functional group?

Answer 12

The part of the molecule which determines how it reacts.

Question 13

What is a homologous series?

Answer 13

All have the same functional group.

Question 13

What is a homologous series?

Answer 13

All have the same functional group.

Question 14

Why could combusting an alkene produce unburnt carbon particles?

Answer 14

Incomplete combustion- when there isn’t enough oxygen.

Question 14

Why could combusting an alkene produce unburnt carbon particles?

Answer 14

Incomplete combustion- when there isn’t enough oxygen.

Question 15

What do you see when alkenes are combusted?

Answer 15

They burn in air with a smoky flame.

Question 16

What is hydrogenation?

Answer 16

Alkene + hydrogen –> alkane

Conditions:
Nickel catalyst
150°C

The two hydrogen atoms add across the double bond, so they’re converted to single bonds.

Question 17

What is hydration?

Answer 17

Alkene + water (steam) <=> alcohol

Conditions:
Water must be in the form of steam
300°C
Pressure of 70 atmospheres.
Phosphoric acid catalyst.

Question 17

What is hydration?

Answer 17

Alkene + water (steam) <=> alcohol

Conditions:
Water must be in the form of steam
300°C
Pressure of 70 atmospheres.
Phosphoric acid catalyst.

Question 18

How do you increase the yield of ethanol in hydration reaction?

Answer 18

Reaction is reversible:

Any unreacted ethene and steam are passed back through the catalyst.

Question 19

Reactions of alkenes and halogens:

Answer 19

React rapidly.

alkene + halogen –> dihaloalkane
The halogen atoms add across the double bond.

Question 19

Reactions of alkenes and halogens:

Answer 19

React rapidly.

alkene + halogen –> dihaloalkane
The halogen atoms add across the double bond.

Question 20

What are the uses of alcohols?

Answer 20

Fuels
Solvents
Alcoholic drinks

Question 21

What are the structural formulas for the first four alcohols?

Answer 21

Methanol
CH3OH
Ethanol
CH3CH2OH
Propanol
CH3CH2CH2OH
Butanol
CH3CH2CH2CH2OH

Question 22

How to make ethanol?

Answer 22

Hydration of ethene:
300°C
70atm
Phosphoric acid catalyst

Advantage:
Produces a high yield of ethanol
Disadvantages:
Requires a high temperature and a lot of energy.
The ethene comes from crude oil and is not renewable.

Fermentation of sugar:
Start with a solution of glucose and mix this with yeast.
The yeast converts the sugar solution to a solution of ethanol.
CO2 is also produced.
Requires a temperature of 30°- doesn’t require a lot of energy.
Must take place in anaerobic conditions.
Sugar comes from plants so is renewable.
Disadvantage:
The product is an aqueous solution of ethanol.
Needs to be purified by distillation which requires energy.

Question 23

Describe alcohols solubility in water:

Answer 23

Soluble in water and form neutral solutions.

As number of carbon atoms increases, the solubility decreases.

Question 24

Alcohols reacting with sodium:

Answer 24

ethanol + sodium –> sodium ethoxide + hydrogen

Question 25

Alcohol reacting with an oxidising agent:

Question 26

What is an example of an oxidising agent?

Answer 26

acidified potassium dichromate