Organic Chem

Question 1

Describe the combustion of hydrocarbons

Answer 1

• exothermic reaction when reacted with o2
• complete combustion- c02 + water
• incomplete - co/ c + water

Question 2

Decribe combustion of alkanes

Answer 2

• 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 3

Alkane properties

Answer 3

• 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 4

Fractional distillation

Answer 4

• Crude oil is heated and vaporised.
• Vapor rises up the fractionating column (tower).
• 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 5

Cracking

Answer 5

When large hydrocarbons are thermally broken down into smaller and useful molecules

Question 6

What type of reaction is cracking

Answer 6

Thermal decomposition

Question 7

Catalytic cracking

Answer 7

Reactant heated to vapor, passed over a hot catalyst (catalytic cracking) (450 degrees)

Question 8

Steam cracking

Answer 8

heated to vapor, mixed with steam and heated to high temperatures (steam cracking) (>800 degrees)

Question 9

Uses for products of cracking

Answer 9

The products are alkanes and alkenes - used as polymers and starting materials for synthesis.

Question 10

Alkene

Answer 10

Unsaturated hydrocarbon. Contains a C=C bond.
General formula for alkenes is: CnH2n

Question 11

Test for alkenes

Answer 11

Add bromine water. Colour change occurs from orange to colourless.

Question 12

Combustion of alkenes

Answer 12

• incomplete - smokey yellow flame carbon monoxide, carbon dioxide and water vapour
• complete - carbon dioxide and water

Question 13

Reaction of alkene with hydrogen

Answer 13

• cc double bond opens to make single cc bond
• hydrogenation; requires a higher temperature and a nickel catalyst

Question 14

Reaction of alkenes with steam

Answer 14

• hydration; requires high temperature, pressure, and a catalyst
• cc double bond opens
• forms alcohol

Question 15

Reaction of alkenes with halogens

Answer 15

Becomes saturated cc double bond opens

Question 16

Alcohol

Answer 16

An organic compound that contains an -OH functional group

Question 17

Characteristics of first 4 alcohols

Answer 17

• 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 18

What happens when alcohoks are oxidised

Answer 18

Carboxylic acids

Question 19

3 uses of alcohols

Answer 19

• Fuels
• Solvents
• Drinks

Question 20

Conditions for fermentation of glucose

Answer 20

37 degrees Celsius, aqueous solution of the glucose, absence of air, yeast added;

Question 21

Carboxylic acid

Answer 21

Organic compounds that contain a COOH functional group

Question 22

Characteristics of carboxylic acids

Answer 22

• Dissolve in water to form an acidic solution (contains 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 23

What type of acid is carboxylic acid

Answer 23

It is a weak acid.

Question 24

Why are carboxylic acids weak

Answer 24

They 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 25

Ester

Answer 25

• An organic compound containing a -COO- functional group
• formed from carboxylic acid and alcohol in the presence of a strong acid catalyst.
• They have a fruity smell.

Question 26

How do molecules eith cc double bonds form polymers

Answer 26

• A polymer is a long chain molecule which is made by lots of smaller molecules joining together.
• C=C bonds open up and many monomers join together to form a chain
• No other products are made.
• It is called an “addition polymerisation” reaction.

Question 27

Condensation polymers

Answer 27

• In this reaction monomers with 2 functional groups form polymer chains
• the polymer is formed, but also a small molecule is released, e.g. H2O, HCI.
• for each new bond a small molecule is lost

Question 28

Amino acid

Answer 28

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

Question 29

How are proteins made

Answer 29

By numerous condensation polymerisation reactions; proteins are polymers made of amino acids (monomers).

Question 30

Polypeptides

Answer 30

made by condensation polymerisation of amino acids, but are shorter than proteins.

One could think about proteins as a product of many polypeptide chains bonded together.

Question 31

Carbohydrates

Answer 31

• They are organic molecules made of C,H, e.g. starch and cellulose.
• Each of these are polymers made of glucose (other carbohydrate) monomers.
• Their structures differ in the way the glucose molecules are joined together.

Question 32

Dna

Answer 32

• Contains genetic material in chromosomes
• made of two polymer chains that are held together in a double helix.
• Each polymer chain can be made from 4 different monomers - nucleotides.