Organic Chemistry

Question 1

What is crude oil? How is it formed?

Answer 1

Crude oil is a finite resource found in rocks. Crude oil is the remains of ancient biomass consisting of mainly plankton that was buried in mud.

Question 2

What is crude oil on a molecular level? What is in crude oil?

Answer 2

Crude oil is a mixture of a very large number of compounds. Most of the componds in crude oil are hydrocarbons, which are molecules made up of hydrogen and carbon atoms only.

Most of the hydrocarbons in crude oil are hydrocarbons called alkanes. The general formula for the homologous series of alkanes is CnH2n+2
The first four members of the alkanes are methane, ethane, propane and butane.

Question 3

What is a hydrocarbon?

Answer 3

A hydrocarbon is a compound made up of hydrogen and carbon atoms only.

Question 4

What is a homologous series?

Answer 4

A homologous series is a series of compounds increasing in size, with similar chemical properties, and trends in physical properties.

Question 5

How are hydrocarbons separated in crude oil? What are they used for?

Answer 5

The many hyrdocarbons in crude oil may be separated into fractions, each of which contains molecules with a similar number of carbon atoms, by fractional distillation.

The fractions can be processed to produce fuels for feedstock or for the petrochemical industry.

Question 6

What fuels are produced from crude oil and what are these used for?

Answer 6

Many useful materials on which modern life depends are produced by the petrochemical industry - e.g solvents, lubricants, polymers and detergents

Liquified Petroleum Gas (LPG), Petrol, Kerosene, Diesel, Heavy Fuel Oil, Bitumen

LPG is used for heating and cooking appliances.
Petrol and diesel are used as fuel for cars. (and LPG apparently).
Kerosene is used for fuel in aircraft.
Heavy Fuel Oil is used for marine fuel. Bitumen is used for tarmac and roads.

Question 7

Why is a vast array of natural and synthetic carbon compounds able to occur?

Answer 7

The vast array of natural and synthetic carbon compounds occur
due to the ability of carbon atoms to form families of similar
compounds.

Question 8

What is fractional distillation in basic terms?

Answer 8

Fractional distillation is the separation of a mixture of liquids with different boiling points.

Question 9

Describe how fractional distillation is used to separate fractions in crude oil.

Answer 9

1. The crude oil is heated and boiled in a furnace until it is vapourised.
2. The vapours are then passed into a fractionating column which has a temperature gradient, so it is hotter at the bottom and cooler at the top.
3. The vapours rise up the column , and fractions will condense at different levels according to their different boiling points.
4. Fractions with a lower boiling point with condense closer to the top of the fractionating column, and fractions with a higher boiling point with condense closer to the bottom of the fractionating column.

Question 10

What are the different properties of hydrocarbons and what do changes in these properties depend on?

Answer 10

Some properties of hydrocarbons depend on the size of their molecules, including boiling point, viscosity and flammability. These properties influence how hydrocarbons are used as fuels.

Question 11

Describe the properties of alkanes.

Answer 11

Alkanes are a homologous series of hydrocarbons (contains C and H). They are saturated hydrocarbons, so each carbon atom has singular covalent bonds. The general formula is CnH2n+2. All alkanes are colourless and odourless.

3 physical properties of alkanes:
Colourless, low density, insoluble in water

Question 12

Describe the trend in properties of alkanes.

Answer 12

A higher chain of alkanes (aka with increasing molecular size) has a higher boiling point, higher viscosity, lower volatility, burns with a smokier flame and is less flammable than a lower chain of alkanes.

(As the length of the carbon chain increases, the: boiling points increases, viscosity increases, volatility decreases, burns with a cleaner flame, flammability decreases.)

Question 13

What does the combustion of hydrocarbons do?

Answer 13

The combustion of hydrocarbon fuels releases energy. During combustion, the carbon and hydrogen in the fuels are oxidised. The complete combustion of a hydrocarbon produces carbon dioxide
and water.

Question 14

What is cracking?

Answer 14

Cracking is the process by which larger, less useful hydrocarbons can be broken down into smaller more useful hydrocarbons, using heat.

Question 15

What two ways can cracking be done and what are the conditions for these two methods?

Answer 15

Cracking can be done by catalytic cracking and steam cracking:

We use a catalyst, held over a high temperature (approx. 500oC).

Steam, held over a high temperature (approx 500oC)

Question 16

What cataylst is used for cracking?

Answer 16

A zeolite, containing aluminium oxide and silicon dioxide.

Question 17

Explain in detail why cracking of crude oil fractions makes them more useful.

Answer 17

The larger crude oil fractions can be broken down to make them more useful because larger molecules don’t flow easily and cracking crude oil fractions makes alkenes. The smaller chains are higher in demand, because the smaller chains can be used as fuels, plastics and polymers.

There is a high demand for fuels with small molecules and so some
of the products of cracking are useful as fuels.

Question 18

What are the products of cracking?

Answer 18

The products of cracking include alkanes and another type of hydrocarbon called alkenes.

Question 19

How can you test for alkenes?

Answer 19

Alkenes are more reactive than alkanes and react with bromine water, which is used as a test for alkenes.

Changing from orange-brown to colourless.

Question 20

What are alkenes used for?

Answer 20

Alkenes are used to produce polymers and as starting materials for the production of many other chemicals.

Question 21

Explain why C8H18 has a lower boiling point than C14H30.

Answer 21

C8H18 has a lower boiling point than C14H30 because C8H18 is a smaller molecule so there are weaker intermolecular forces / weaker intermolecular forces so less energy required to break.

Question 22

Alkenes are obtained from crude oil using fractional distillation followed by cracking.
Explain how alkenes are produced using fractional distillation followed by cracking.

Answer 22

Crude oil heated/boiled/vapourised.
Fractionating column used.
Fractions have different boiling points.
Collum hotter at the bottom and colder at the top.
Fractions condense at different levels.
Heavy fractions collected at the bottom or light fraction collected at the top.
Cracking
High temperature
Catalyst or steam
Large molecule splits into small molecule
Mixture of alkanes and alkenes produced.

Question 23

Differences between alkanes and alkenes

Answer 23

Alkanes are saturated hydrocarbons, and cannot undergo addition reactions. Alkenes are unsaturated hydrocarbons and can undergo addition reactions.

Question 24

Properties of alkenes

Answer 24

Alkenes are hydrocarbons with a double carbon-carbon bond. The general formula for the homologous series of alkenes is CnH2n
Alkene molecules are unsaturated because they contain two fewer
hydrogen atoms than the alkane with the same number of carbon atoms.
The first four members of the homologous series of alkenes are ethene, propene, butene and pentene.

Question 25

Function group for alkenes. What is functional group?

Answer 25

Alkenes are hydrocarbons with the functional group C=C. It is the generality of reactions of functional groups that determine the reactions of organic compounds.

Question 26

Why aren't alkenes used in combustion reactions?

Answer 26

Alkenes react with oxygen in combustion reactions in the same way as other hydrocarbons, but they tend to burn in air with smoky flames because of incomplete combustion.

Question 27

What can alkenes react with and what happens to the bonds in alkenes when these reactions take place?

Answer 27

Alkenes react with hydrogen, water and the halogens, by the addition of atoms across the carbon-carbon double bond so that the double bond becomes a single carbon-carbon bond

Question 28

What are the conditions for addition reacts of alkenes with 3 other substances?

Answer 28

Alkenes can react with halogens e.g bromine and ethene, which produces dibromoethane (colourless). Makes a halo-ethane Conditions: atmospheric pressure, room temperature, no catalyst Alkenes can react with steam(high temperature with concentrated phosphoric acid catalyst) to produce alcohols, e.g ethene can react with steam over a catalyst to produce ethanol. Makes an alcohol. Conditions: high temperature, phosphoric acid catalyst, high pressure The reaction is reversible, so it is recyclable. Alkenes can react with hydrogen to make alkanes. Conditions: 60 degrees, nickel catalyst

Question 29

What is the functional group for alkanes?

Answer 29

Trick question - alkanes lack a functional group

Question 30

Functional group of alcohols

Answer 30

-OH

Question 31

First four members of the homologous series of alcohols

Answer 31

Methanol, Ethanol, Propanol, Butanol

Question 32

Give the structural formula of ethanol

Answer 32

CH3CH2OH (Shortened to C2H5OH)

Question 33

What are the two ways you can make ethanol (alcohols in general) and what are the chemical symbol equations for them?

Answer 33

Through fermentation glucose -- yeast --> ethanol + carbon dioxide Aqeuous solutions of ethanol are produced when sugar solutions are fermented with yeast. c6h12o6 --> c2h5oh + co2 Ethene + water -- catalyst --> ethanol c2h4 + h2o + c2h5oh

Question 34

Conditions for fermentation

Answer 34

Sugars dissolved in water, and mixed with yeast an air lock to allow carbon dioxide out, while stopping air getting in warm temperatures, 25-35 degrees

Question 35

What happens when aochols combust (burn in air)

Answer 35

ehtanol + oxygen --> carbon dioxide + water

Question 36

What happens when alcohols react with sodium

Answer 36

makes sodium alcoxide + hydrogen sodium effervesces (gives off bubbles of gas) when reacting with ethanol not as vigorous as between sodium + water sodium + ethanol --> sodium ethoxide (2C2H5ONa) + hydrogen The other 4 undergo similar reactions

Question 37

Oxidation of alcohols

Answer 37

Will give different products with different oxidising agents With acidified potassium dichormat (VI) solution, it makes carboxylic acid (same thing happens when alcohols are exposed to air, due ot microbes of air - why wine smells like vinegar if open too long) ethanol + oxygen from oxidising agent --> ethanoic acid + water c2h4oh + 2[o] --> ch3cooh + water

Question 38

main uses of alcohols

Answer 38

alcoholic drinks, solvents (marker pens, medicines, cosmetics), fuels, disinfectant

Question 39

Functional group of carboxylic acids

Answer 39

- COOH

Question 40

First four members of homologous series of carboxylic acids and structure

Answer 40

The first four members of a homologous series of carboxylic acids are methanoic acid, ethanoic acid, propanoic acid and butanoic acid. CH3COOH

Question 41

Carboxylic reaction with carbonate

Answer 41

Typical reaction of all acids carboxylic acid + metal carbonate --> salt + water + carbon dioxide eg sodium ethanoate is 2CH3COONa

Question 42

carboxylic acids dissolving in water

Answer 42

dissolve in water to form acidic solutions with pH values less than 7

Question 43

Carboxylic acids reacting with alcohols

Answer 43

Carboxylic acids and alcohols react to make esters Water is also formed in this reversible reaction Sulphuric acid catalyst used ethanoic acid + ethanol < --- sulphuric acid catalyst ---> ethyl ethanoate + water

Question 44

Why are carboxylic acids weak

Answer 44

in water all acids ionise, molecules split up to from h= ions and negative ions (like ch3coo-). Strong acids ionise completely, whereas weak acids do not only small proportion oionisis, and reaction is reversible Carboxylic acids are weak acids. This means that their solutions do not contain many hydrogen ions compared with a solution of a strong acid with the same concentration. The pH of a weak acid will be higher than the pH of a strong acid, if their concentrations are the same. In a solution of a strong acid, the molecules are fully ionised, but in a weak acid, very few of the molecules are ionised. carboxylic acids gently fizz when reacting with carbonates CH3COOH --> CH3COO- + H+ all aqeous

Question 45

Properites of esters

Answer 45

Esters have distinctive smells Are volatile (evaporate easily) Smell sweet and fruity - ideal for perfumes and flavourings

Question 46

What is addition polymerisation

Answer 46

In addition polymerisation reactions, many small molecules (monomers) join together to form very large molecules (polymers), with no addition product forming. the repeating unit in a polymer is a monomer.

Question 47

What is a polymer, what is a monomer?

Answer 47

Alkenes can be used to make polymers such as poly(ethene) and poly(propene) by addition polymerisation. A large molecule formed from many identical smaller molecules known as monomers.

Question 48

What is condensation polymerisation?

Answer 48

Condensation polymerisation involves monomers with two functional groups. When these types of monomers react they join together, usually losing small molecules such as water, and so the reactions are called condensation reactions. Condensation polymerisation is the joining of two monomers with different functional groups, to form a polymer and a small molecule like water.

Question 49

What is a polyester, how is it formed and what are its uses?

Answer 49

Polyesters occur naturally as biological polymers, but can also be made artificially. Man-made polymers are often used in clothing. Polyesters are an example of a condensation polymer. A simple polyester can be made from a monomer which has two hydroxyl groups (-OH) and another monomer which has two carboxylic acid groups (-COOH).

Question 50

What is an amino acid, how do they react to produce what

Answer 50

Amino acids have two different functional groups in a molecule. All amino acids contain the -NH2 group and the carboxylic acid group -COOH Amino acids react by condensation polymerisation to produce polypeptides (and one molecule of water for every amino acid added). Different amino acids can be combined in the same chain to produce proteins.

Question 51

What is DNA

Answer 51

DNA (deoxyribonucleic acid) is a large molecule essential for life. DNA encodes genetic instructions for the development and functioning of living organisms and viruses.

Question 52

Structure of DNA

Answer 52

Most DNA molecules are two polymer chains, made from four different monomers called nucleotides, in the form of a double helix.

Question 53

Name the 4 different naturally occurring polymers you need to know about and the monomers that are used to make them.

Answer 53

DNA: 4 different types of monomer called nucleotides. millions of nucleotides --> DNA (a polynucleotide) + water Proteins: Amino acid are the monomers Ptroeins are made of polypetides. A polypetid is a long molcule made from smaller molecules called amino acids. Cellulose and starch: sugar molecules are the monomers glucose monomers --> starch/cellulose polymers + water Polysaccarides (eg starch) are made of long molecules of monosaccharides (eg glucose)