Organic

Question 0

What are hydrocarbons

Answer 0

Compounds containing the elements hydrogen and carbon only

Question 1

What is organic chemistry?

Answer 1

A branch of chemistry which studies the many compounds which the element carbon forms

Question 2

Why are Hydrocarbons important?

Answer 2

A) used as fuels e.g methAne in natural gas used in bunsens
Propane and butane- bottle gas (BBQ)
B) are monomers used to make polymers( plastics)

Question 3

Give a main source of hydrocarbons

Answer 3

Crude oil

Question 4

What happens in fractional distillation

Answer 4

Raw crude oil undergoes Frac. Distill. - the different sized hydrocarbons are separated out from each other

Question 5

What are aliphatic hydrocarbons?

Answer 5

Molecules contain:
A straight chain
A branched chain
A ring of carbon atoms

Question 6

Was a aromatic hydrocarbons?

Answer 6

These molecules contain benzene ring

Question 7

What is a saturated hydrocarbon?

Answer 7

• Contain single covalent bonds between the carbon atoms

- Undergo Substitution reactions

Question 8

What are unsaturated hydrocarbons?

Answer 8

• Contain at least 1 multiple ( double or triple) bond between two carbon atoms
• Undergo addition reactions

Question 9

How could you test for unsaturation?

Answer 9

A) red bromine water -> colourless

B) ACIDIFIED KMnO4 purple -> colourless

Add X to test tube & shake

Question 10

What is a homologous series?

Answer 10

A family of organic compounds

All the members of the family

1. Have the same general formula
2. have similar method of preparation
3. Have similar chemical properties
4. Contain the same functional group

Question 11

What is a functional group?

Answer 11

A group of atoms common to all members of a homologous series

Determine the properties

Question 12

How is methane a useful fuel?

Answer 12

1. Easily piped
2. Relatively cheap
3. Relatively clean

Question 13

Give two properties of the alkanes

Answer 13

1. Non-polar molecules but contain slightly polar covalent bonds
2. Virtually insoluble in water

Question 14

Explain the intra molecular bonding of the alkanes

Answer 14

C-H bonds are slightly polar covalent
HOWEVER: the overall molecule is non-polar
Due to its shape/ symmetry, the centre of positive charge coincides with the centre of negative charge

Question 15

Explain why propane has a lower boiling point than butane

Answer 15

• Propane is a smaller molecule i.e. Smaller relative mol. mass
• contains fewer electrons
• weaker intermolecular forces, easier to break

Question 16

What is a substitution reaction?

Answer 16

Undergone by saturated compounds e.g. alkanes

One atom or group of atoms in a molecule is replaced by another atom or group of atoms

Question 17

Name one reagent which the alkanes react with

Answer 17

Chlorine - Cl2

MUST HAVE U.V. LIGHT

Question 18

Write an equation for the reaction between methane and chlorine

Answer 18

CH4 + Cl2 —–> CH3Cl + HCl

Question 19

Give and use of chloromethane and chloroethane

Answer 19

Used as solvents in dry cleaning

Question 20

What is a reaction mechanism?

Answer 20

A reaction mechanism shows the different stages / steps which take place during a reaction in order for products to be formed

Question 21

Name two types of mechanisms

Answer 21

Free radical substitution

Ionic addition

Question 22

What mechanism occurs during the mono chlorination of methane

Answer 22

Free radical substitution mechanism. During this mechanism intermediate species called free radicals form i.e a highly reactive species with an unpaired electron

Question 23

Give 2 features of an elimination reaction

Answer 23

1. A small molecule is taken from a large molecule

2. Unsaturated product formed

Question 24

Give 2 uses of methanol

Answer 24

- oxygenate added to petrol to increase the octane no. and reduce air pollution - added to industrial alcohol to stop consumption of this alcohol

Question 25

Give a use of methanal

Answer 25

A solution of methanal is used as an embalming fluid

Question 26

Give a use of methanoic acid

Answer 26

A weak acid found in stinging ants and nettles

Question 27

Give 4 uses of ethanol

Answer 27

- alcoholic drinks - oxygenate - solvent in cosmetics ( perfume) - used to make soaps i.e. solvent for veg. oil or animal fat

Question 28

Where would ethanal be found

Answer 28

Formed in the human body ie metabolite from ethanol | W

Question 29

Give 2 uses of ethanoic acid

Answer 29

To make vinegar | To make cellulose acetate for use in varnishes

Question 30

Give a use of propanoic acid

Answer 30

Food preservation - stops growth of moulds

Question 31

Give a use for propan-2-one

Answer 31

Solvent used in nail varnish remover

Question 32

Why do alcohols have higher boiling point than their corresponding alkanes or alkenes

Answer 32

The intermolecular forces between alcohol molecules are hydrogen bonds. Alkanes and alkenes have weaker Van der Waals forces

Question 33

Name an aromatic aldehyde found in almond kernels

Answer 33

``` Benzaldehyde H | C = O | _ / o\ \ _/ ```

Question 34

Give one way of forming an aldehyde in the lab

Answer 34

Oxidize a primary alcohol, using an oxidising agent such as acidified sodium dichromate or acidified KMnO4

Question 35

How would you reduce an aldehyde to an alcohol?

Answer 35

Heat the aldehyde with hydrogen ( reducing agent ) | Use a nickel catalyst

Question 36

Name the first 2 members of the ketone _____ | |

Answer 36

Propan-2-one | Butan-2-one

Question 37

How would you distinguish between an aldehyde and acetone in the lab

Answer 37

Mix an equal volume of Fehlings A+B ( blue colour) Place in test tubes, add aldehyde to one and ketone to another in a water bath ( heat) Aldehyde-> a brick red precipitate of copper 1 oxide forms Ketone -> no brick red precipitate forms Why? Aldehydes are easily oxidized by the Fehlings to a carboxylic acid. The C=O group in ketones is surrounded by an alkyl group on each side making it difficult to oxidise