12 & 13. Organic Chemistry

Question 1

General formulae

Answer 1

(a) alkanes, CnH2n+2

(b) alkenes, CnH2n

(c) alcohols, CnH2n+1OH

(d) carboxylic acids, CnH2n+1COOH

Question 2

Describe a homologous series and its characteristics.

Answer 2

A homologous series is a family of similar compounds with similar chemical properties due to the presence of the same functional group.

(a) having the same functional group
(b) having the same general formula
(c) differing from one member to the next by a –CH2– unit
(d) displaying a trend in physical
(e) sharing similar chemical prop

Question 3

Functional group
Structural formula
Structural isomers

Answer 3

an atom or group of atoms that determine the chemical properties of a homologous series.

an unambiguous description of the way the atoms in a molecule are arranged.

compounds with the same molecular formula, but different structural formulae.

Question 4

Saturated compounds and unsaturated compounds.

Answer 4

a saturated compound has molecules in which all carbon–carbon bonds are single bonds.

an unsaturated compound has molecules in which one or more carbon–carbon bonds are not single bonds.

Question 5

Name the fossil fuels

main constituent of natural gas

Hydrocarbons

Petroleum

Separation of petroleum

Answer 5

coal, natural gas and petroleum

methane

compounds that contain H2 and C ONLY

is a mixture of hydrocarbons

fractional distillation

Question 6

Properties of fractions obtained from petroleum change from down to up fractionating column.

Answer 6

(a) decreasing chain length
(b) higher volatility
(c) lower boiling points
(d) lower viscosity

Question 7

Uses of the fractions- up to down

Answer 7

(a) refinery gas fraction for gas used in heating and cooking

(b) gasoline /petrol fraction for fuel used in cars

(c) naphtha fraction as a chemical feedstock

(d) kerosene /paraffin fraction for jet fuel

(e) diesel oil/ gas oil fraction for fuel used in diesel engines

(f) fuel oil fraction for fuel used in ships and home heating systems

(g) lubricating oil fraction for lubricants, waxes and polishes

(h) bitumen fraction for making roads

Question 8

a substitution reaction

addition reaction

Answer 8

one atom or group of atoms is replaced by another atom or group of atoms.

in an addition reaction only one
product is formed.

Question 9

Alkanes- bonding, manufacture, properties, reactivity

Answer 9

single covalent and are saturated
hydrocarbons. fractional distillation

P- colourless, odourless, insol in water, sol in organic solvents, low MP/BP- gradually inc with C no. gas in rt

C- generally unreactive, except combustion and substitution by chlorine.

substitution reaction with chlorine as a photochemical reaction, with ultraviolet light providing the activation energy, Ea. 2 products.

Question 10

Alkenes- bonding, manufacture, properties, reactivity

Answer 10

double carbon–carbon covalent bond and are unsaturated hydrocarbons

cracking of larger alkane molecules using a high temperature and a catalyst to convert long chain alkanes into shorter chain alkane and alkenes.

(a) halogenation- aqueous bromine- brown to colourless

(b) hydrogenation- hydrogen- 200°C nickel catalyst- alkane

(c) hydration- steam- 300°C and 6000kPa /60 atm & phosphoric (v) acid catalyst.

Question 11

Alcohols- manufacture of ethanol, uses

Answer 11

(a) fermentation of aqueous glucose at 25–35°C in the presence of yeast (enzyme) and in the absence of oxygen

(b) catalytic addition of steam to ethene at 300°C and 6000kPa /60 atm in the presence of an acid catalyst

(a) a solvent
(b) a fuel

Question 12

Describe the advantages and disadvantages of the manufacture of ethanol by:

(a) fermentation
(b) catalytic addition of steam to ethene

Answer 12

1. simple set up- complex set-up
2. renewable- non-renewable
3. batch process- continuous process
4. slow- fast
5. 15% yield- 96% yield

Adv- F- 1, 2
C- 3, 4, 5

Question 13

Carboxylic acid- bonding, manufacture of ethanoic acid, properties, reactivity

Answer 13

OXIDATION of ethanol

ethanol+ O2 → ethanoic acid + water

(a) with acidified aqueous potassium manganate(VII)- O2 from PM.

(b) by bacterial oxidation during vinegar production- O2 from vinegar

Question 14

Esters

Answer 14

reaction of a carboxylic acid with an alcohol using an acid catalyst to form an ester. concentrated H2SO4. reversible reaction.

ethanol + propanoic acid => ethyl propanoate + water

displayed and molecular formula- acid and then alcohol

Question 15

polymers

Answer 15

large molecules built up from
many smaller molecules called monomers.

formation of poly(ethene) is an
example of addition polymerisation using ethene monomers.

Question 16

Describe the differences between addition and condensation polymerisation

Answer 16

A- monomer units add together to form only one product, polymer.

C- two different monomers are linked together, arranged alternately, with the removal of a small molecule, usually water.

Question 17

environmental challenges caused by plastics

Answer 17

plastics are made from polymers

(a) disposal in land fill sites
(b) accumulation in oceans
(c) formation of toxic gases from burning

Question 18

polyamides and polyesters- monomers and examples

Answer 18

(a) polyamides from a dicarboxylic acid and a diamine- amide linkage formed. Nylon is a polyamide. (loss of one water molecule). ( -COOH and -NH2 react).

(b) polyesters from a dicarboxylic acid and a diol. PET can be converted back into
monomers and re-polymerised. (loss of one water molecule). (-COOH and -OH react).

(c) proteins as natural polyamides and that they are formed from amino acid monomers with the general structure.