7-Organic Chemistry (2)

Question 1

What are hydrocarbons?

Answer 1

compounds that contain hydrogen and carbon only

Question 2

2What are Alkanes?

Answer 2

• simplist type of hydrocarbon
• CnH2n+2
• homologous series - all react in a similar way
• saturated compounds, each carbon atom forms four single covalent bonds
• first four alkanes methane CH4, ethane C2H6, propane C3H8, butane C4H10

Question 3

What are short chain hydrocarbon’s like?

Answer 3

• more runny, less viscous
• more volatile, lower boiling point - more flammable - used for fuels

Question 4

What is complete combustion?

Answer 4

• burning of hydrocarbon’s with pleanty of oxygen
• hydrogen + oxygen -> carbon dioxide + water

Question 5

What is crude oil?

Answer 5

• remains of animals and plants, mainly plankton
• can be drilled up from rocks and seperated into useful oils through fractional distillation

Question 6

How does fractional distillation work?

Answer 6

• heated till most turned into gas then put into fractioning collumn
• hot at bottom of column and cooler as you go up - temperature gradient
• longer hydrocarbons have higher boiling points and shorter have lower, so condense into liquids and drain out earlier on
• longer condense into liquids higher up the column
• crude oil mixture seperated into useful products

Question 7

What are the uses of crude oil?

Answer 7

• fuel for transport
• some used as feedstock to make new compounds for use in polymers, solvents, lubricants, detergents

Question 8

What is cracking?

Answer 8

• splitting up of long chain hydrocarbonds to make shorter, more useful ones
• cracking produces alkenes aswell
• some products of cracking used as fuel

Question 9

What are the different methods of cracking?

Answer 9

• Thermal decomposition - breaking molecules down by heating them, first vapourised then passed over hot powdered aluminium oxide catalyst and long - chain molecules split apart - catalyctic cracking
• Vaporise and mix with steam and heat to very high temperatures - steam cracking

Question 10

What are alkenes?

Answer 10

• double C bond - unsaturated hydrocarbons, open up to form single bons - highly reactive
• Ethene C2H4, Propene C3H6, Butene C4H8, Pentene C5H10
• formula CnH2n

Question 11

What is incomplete combustion of Alkene’s like?

Answer 11

• results in smoky yellow flame and less energy
• alkene + oxygen -> carbon + carbon monoxide + carbon dioxide + water

Question 12

How do Alkene’s react?

Answer 12

• addition reactions
• all react in similar ways as in the same functional group
• carbon double bond opens up to a single bond and a new atom added to each carbon

Question 13

What is hydrogenation?

Answer 13

• addition of hydrogen to Alkanes
• double bond carbon’s open up
• alkene reacted with hydrogen in the pressure of catalyst

Question 14

How are alcohols formed from alkenes?

Answer 14

• when alkenes react with steam and water added across double bond
• ethanol made by mixing ethene with steam and passing over catalyst

Question 15

How do the halogens react with Alkenes?

Answer 15

• Alkenes react in adition reactions with halogens such as bromine, chlorine, and iodine
• form saturated molecules with C=C carbon each becoming bonded to a halogen atom
• e.g bromine and ethene react to form dibromoethane

Question 16

How do you test for alkenes?

Answer 16

• add bromine water and shake - goes colourless

Question 17

What are Alcohols like?

Answer 17

• general formula CnH2n+1OH
• alcohols flammable
• undergo complete combustion in air produce carbon dioxide and water
• can be made by fermentation - sugar (yeast ->) ethanol +carbon dioxide

Question 18

What are carboxylic acids like?

Answer 18

• functional group -COOH
• names end in -anoic acid
• react like other acids but salts end in -anoate e.g ethanoate
• can dissolve in water and ionise to release H+ ions, don’t completely ionise

Question 19

How can esters be made?

Answer 19

• from an alcohol and carboxylic acids
• functional group -COO
• acidic catalyst usually used
• alcohol + carboxylic acid -> ester + water

Question 20

What is condensation polymerisation?

Answer 20

• making polymers using monomers from different functional groups
• monomers react together and bond forms between them to make polymer chains
• for each new bond that forms, a small molecule, e.g water is lost

Question 21

How are addition and condensation polymerisation different?

Answer 21

• addition contains 1 monomer type and C=C bond whereas condensation involves 2 monomer types each containing 2 of the same functional groups or 1 monomer type with 2 different functional groups
• addition forms 1 product, condensation forms 2 types of products, polymer and small molecule
• addition produces carbon-cabron double bond in monomer, condensation has two reactive groups on each monomer

Question 22

What are some examples of naturally occuring polymers?

Answer 22

• Proteins - polymers of amino acids
• DNA made form nucleotide polymers
• simple sugars can form polymers