Organic Chemistry

Question 1

Crude oil

Answer 1

Finite resource formed over millions of years from the remains of plankton which were buried in mud. Mixture of hydrocarbons (molecules made up of only hydrogen and carbon atoms).

Question 2

Alkanes

Answer 2

General formula - CnH2n+2.
Saturated molecules as carbon atoms are fully bonded to hydrogen atoms, only single bonds, used as solvents and fuels.

Question 3

Alkenes

Answer 3

General formula - CnH2n.
Unsaturated molecules because they have 2 fewer hydrogen than the equivalent alkane, contain a double bond, used to make polymers, burn in air with a smokey flame, more reactive than alkanes.

Question 4

Viscosity

Answer 4

Thickness of a fluid. As size of hydrocarbon molecule increases, viscosity increases.

Question 5

Flammability

Answer 5

How easily a hydrocarbon burns. As size of hydrocarbon molecule increases, flammability decreases.

Question 6

Boiling point

Answer 6

Temperature at which hydrocarbon turns into gas. As size of hydrocarbon molecule increases, boiling increases.

Question 7

Combustion

Answer 7

Hydrocarbon fuels release energy when combusted. During combustion, carbon and hydrogen atoms in the fuel react with oxygen (they are oxidised). In complete combustion, oxygen is unlimited and carbon dioxide and water is produced

Question 8

Fractional distillation

Answer 8

1. Crude oil is heated to high temperatures so all hydrocarbons evaporate.
2. Crude oil vapour rises up the fractionating column where it is cooler at the top.
3. Hydrocarbons condense when they reach their boiling point.
4. The liquid fractions are removed and the remaining hydrocarbons continue moving up until they reach their boiling points and condense.

Long chain hydrocarbons condense at the bottom. Very short chain hydrocarbons do not condense and are removed from the top as gases.

Question 9

Feedstock

Answer 9

A chemical that is used to make other chemicals.
Some fractions are used as feedstock in petrochemical industry.

Question 10

Cracking

Answer 10

High demand for short-chain hydrocarbons to be used as fuels.
Long-chain alkane is broken down to produce a short-chain alkane and an alkene.

Question 11

Testing for alkenes

Answer 11

Orange bromine water turns colourless.

Question 12

Functional group

Answer 12

Part of a molecule that determines how it reacts.

Question 13

Homologous series

Answer 13

A group of chemicals which have similar properties with the same functional group/with the same general formula.

Question 14

Hydrogenation

Answer 14

Reaction of alkenes with hydrogen. Requires 150°C and nickel catalyst.
Carbon-carbon double bound coverts into a carbon-carbon single bond and 2 hydrogens are added. Produces an alkane.

Question 15

Hydration

Answer 15

Reaction of alkenes with water in the form of steam. Requires 300°C, 70 atm and phosphoric acid as a catalyst.
Carbon-carbon double bond is converted into a carbon-carbon single bond and OH is added across.
Reversible reaction that produces an alcohol.

Question 16

Reaction with halogens

Answer 16

Alkenes react with halogens.
Carbon-carbon double bond is converted to carbon-carbon single bond and the halogen atoms add across.
Produces di-(halogen)(alkane equivalent of alkene) e.g. ethene + bromine -> dibromoethane.

Question 17

Hydration of ethene

Answer 17

PROS: produces high yield of ethanol
CONS: requires high temperature + energy, comes from crude oil and is non-renewable.

Question 18

Alcohols

Answer 18

not rlly a general formula but add C-O-H to the alkanes displayed formula.
Used as fuels, solvents and found in alcoholic drinks.

Question 19

Fermentation

Answer 19

Glucose mixed with yeast, converts the glucose to a solution of ethanol and also produces CO₂.
Conditions: 30°C, anaerobic.
PROS: low temp so not a lot of energy, comes from plants so renewable
CONS: ethanol produced is aqueous so needs to be purified by distillation which requires energy.

Question 20

Solubility of alcohols

Answer 20

Soluble in water, form neutral solutions. As the number of carbon atoms increases, the solubility (ability to dissolve in water) decreases.

Question 21

Reaction of alcohol and sodium

Answer 21

Produces a sodium (alcohol)oxide and hydrogen. e.g. methanol + sodium -> sodium methoxide + hydrogen.

Question 22

Combustion of alcohols

Answer 22

Alcohols release energy when combusted. Combusting an alcohol in air produces carbon dioxide and water.

Question 22

Reaction of alcohol and oxidising agent

Answer 22

e.g. acidified potassium dichromate. Produces a carboxylic acid and water.

Question 23

Carboxylic acids and water

Answer 23

Carboxylic acids only partially ionise in aqueous solutions so are weak acids.

Question 24

Reaction of carboxylic acids and metal carbonate

Answer 24

Produces a salt, carbon dioxide and water e.g. propanoic acid + potassium carbonate -> potassium propanoate + water + carbon dioxide

Question 25

Reaction of carboxylic acids and alcohols

Answer 25

Produces an ester and water e.g. ethanoic acid + ethanol -> ethyl ethanoate + water: a reversible reaction, uses sufuric acid catalyst.
Esters have a pleasant smell so are useful in foods and perfumes.

Question 26

Addition polymers

Answer 26

The monomer is an alkene. The double carbon-carbon bonds in the monomer is converted to single carbon-carbon bonds in the polymer. Name = poly(alkene).

Question 27

Condensation polymers

Answer 27

Made from two different monomers, each with two of the same functional group e.g. ethane diol (has 2 alcohol groups) and hexanedioic acid (2 carboxylic acid groups).
Forms a polyester and water.

Question 28

Amino acids

Answer 28

Have two different functional groups - amine group and carboxylic acid group.
React with each other to form water and a condensation polymer called a polypeptide since it’s from only 1 type of amino acid.

Question 29

DNA

Answer 29

Consists of two polymer chains made from monomers called nucleotides (A,T, C, G), which wrap around each other to form a double helix.

Question 30

Naturally occurring polymers

Answer 30

Starch and cellulose are polymers of glucose, proteins are polymers of amino acids.