Organic Chemistry

Question 1

What is crude oil?

Answer 1

crude oil is a mixture of compounds; a fossil fuel consisting of the remains of ancient biomass
it is a finite resource - it cannot be replaced as it is used up

Question 2

What is a hydrocarbon?

Answer 2

a compound made up exclusively of hydrogen and carbon atoms

Question 3

What are alkanes?

Answer 3

saturated hydrocarbons of a general formula CnH2n+2

Question 4

What is a homologous series?

Answer 4

series of compounds with same general formula, same functional groups and similar chemical properties

Question 5

Describe the combustion of hydrocarbons

Answer 5

• exothermic reaction occurring when hydrocarbons are reacted with oxygen
• complete combustion produces carbon dioxide and water (carbon and hydrogen atoms are completely oxidised)
• incomplete combustion produces carbon or carbon monoxide and water

Question 6

Describe the physical properties of alkanes

Answer 6

• first few in series are gases, then change to liquids, then to solids
• in general, boiling points and viscosity increase as molecules get bigger
• volatility and flammability decrease as molecules get bigger
• poor reactivity

Question 6

Explain how fractional distillation of crude oil takes place

Answer 6

• crude oil is heated and vaporised
• vapor rises up the fractionating column
• the column is hotter at the bottom and cooler at the top
• hydrocarbons cool as they go up the column and condense at different heights, as they have different boiling points
• large molecules, high boiling points - collected at the bottom
• small molecules, low boiling points - collected at the top
• this gives fractions, which can be used in various ways

Question 7

What is cracking?

Answer 7

when large hydrocarbons are thermally broken down into smaller and more useful molecules

Question 8

What type of reaction is cracking?

Answer 8

thermal decomposition

Question 9

What are the conditions for cracking?

Answer 9

reactant heated to vapor, passed over a hot catalyst (catalytic cracking) or heated to vapor, mixed with steam and heated to high temperatures (steam cracking)

Question 10

How are the products of cracking used?

Answer 10

the products are alkanes or alkenes - used as polymers and starting materials for synthesis

Question 11

What is an alkene?

Answer 11

unsaturated hydrocarbon, contains a C=C bond
general formula: CnH2n

Question 12

What is the test for alkenes?

Answer 12

add bromine water, colour change occurs from orange to colourless

Question 13

Describe the combustion of alkenes

Answer 13

they burn with smoky flames due to incomplete combustion

Question 14

Describe addition reactions of alkenes

Answer 14

addition atoms across the carbon-carbon double bond so that the double bond becomes a single carbon-carbon bond
a) with hydrogen - hydrogenation; requires a higher temperature and a nickel catalyst
b) with steam - hydration; requires a higher temperature, pressure and concentrated phosphoric acid (H3PO4) as a catalyst
c) with Br/Cl/I - addition of halogens

Question 15

What is an alcohol?

Answer 15

an organic compound that contains an -OH functional group

Question 16

State 4 characteristics of methanol, ethanol, propanol and butanol

Answer 16

• dissolve in water to form a neutral solution
• react with sodium to form hydrogen
• burn in oxygen
• react with carboxylic acids in presence of acid catalyst to form esters

Question 17

Oxidation of the alcohols leads to…?

Answer 17

carboxylic acids

Question 18

What are 3 uses of alcohols?

Answer 18

• fuels
• solvents
• drinks

Question 19

State the conditions required for fermentation of glucose and state the equation of the reaction

Answer 19

30 degrees celsius, aqueous solution of the glucose, absence of air, yeast added;
C6H12O6 –> 2 CH3CH2OH + 2 CO2

Question 20

What are carboxylic acids?

Answer 20

organic comopunds that contain a COOH functional grouo

Question 21

State characteristics of carboxylic acids

Answer 21

• dissolve in water to form an acidic solution (H+ ions)
• react with metal carbonates to form carbon dioxide
• react with alcohols with an acid catalyst to produce esters
• react with metals to give off hydrogen gas

Question 22

What type of acid is carboxylic acid? (weak/strong)

Answer 22

it is a weak acid

Question 23

Explain why carboxylic acids are weak acids

Answer 23

they are partially dissociated in water, thus the pH of a carboxylic acid in solution is not as low as a solution of a strong acid of the same concentration

Question 24

What is an ester and how is it formed?

Answer 24

an organic compound containing a -COO- functional group, formed from carboxylic acid and alcohol in the presence of a sulfuric acid catalyst
they have a fruity smell (fun!)

Question 25

What is a polymer? How do molecules containing C=C bond form polymers?

Answer 25

a polymer is a long chain molecule which is made by lots of smaller molecules joining together

C=C bonds open up and many smaller molecules (monomers) join together to form a chain (a polymer). No other products are made

it is called an “addition polymerisation” reaction

Question 26

Give 3 examples of addition polymers and their uses

Answer 26

polyethene - plastic bags
(poly)tetrafluoroethene (PTFE) - teflon surfaces, for use in non-stick kitchenware
(poly)chloroethene (polyvinylchloride, PVC) - water pipes
(sorry if those are spelt wrong. I’m actually falling asleep while typing these up, but gotta keep barry the bunny happy yk)

Question 27

What is the repeating unit of a polymer?

Answer 27

it is a smallest structure which, upon numerous translations, yields the structure of the polymer

in addition polymers: to draw it, take a monomer, change C=C to C-C and show additional single bonds extending away from these carbons

Question 28

What is a condensation polymer?

Answer 28

• it is a polymer made in condensation polymerisation
• in this reaction, many molecules join together; the polymer is formed, but also a small molecules is released, e.g. H2O, HCl
• 2 main groups are polyesters (insert joke here), e.g. terylene (or molly woodcock) and polyamides, e.g. nylon

Question 29

What is an amide bond?

Answer 29

an amide bond is similar to the ester bond, with O replaced by N, e.g. (C=O)-NH2
just like an ester, it contains the C=O group

Question 30

What is an amino acid?

Answer 30

it is an organic compound that contains both a carboxylic acid functionality (COOH) and an amine functional group (-NH2)

Question 31

How do amino acids make proteins? What are polypeptides?

Answer 31

by numerous condensation reactions; proteins are polymers made of amino acids (monomers)
*polypeptides are also made by condensation polymerisation of amino acids, but are shorter than proteins, you could think about proteins as a product of many polypeptide chains bonded together

Question 32

What are carbohydrates?

Answer 32

they are organic molecules made of C,H and O, they are biologically relevant, e.g. starch and cellulose
both of these are polymers made of glucose (other carbohydrate) monomers, their structures differ in the way the glucose molecules are joined together

Question 33

What is DNA? Describe its role and structure

Answer 33

DNA is a material that makes up chromosomes - cell structures that store genetic information
DNA is made of 2 polymer chains that are held together in a double helix
each polymer chain can be made from 4 different monomers - nucleotides