Chapter 14

Question 1

Name and draw the structures of methane, ethane, ethene, ethanol, ethanoic acid and the products of the reactions

Answer 1

ok

Question 2

State the type of compound present, given a chemical name ending in -ane, -ene, -ol, or -oic acid or a molecular structure

Answer 2

Alkane: This is the most basic organic compound and usually consists of only C–C bonds and C–H bonds.
Alkene: This indicates that there is a C=C (carbon to carbon) double bond present.
Alcohol: This indicates that there is an O–H group present.
Carboxylic acid: This shows there is a carbon which has a C=O double bond with oxygen, and a single bond to an OH group.

meth-   contains one carbon atom
eth-      contains two carbon atoms
prop-    contains three carbon atoms
but-      contains four carbon atoms
pent-     contains five carbon atoms.

Question 3

Name and draw the structures of the unbranched alkanes, alkenes (not cis-trans), alcohols and acids containing up to four carbon atoms per molecule

Answer 3

ok.

Question 4

Name and draw the structural formulae of the esters which can be made from unbranched alcohols and carboxylic acids, each containing up to four carbon atoms

Answer 4

ok.

Question 5

Name the fuels

Answer 5

coal, natural gas and petroleum

Question 6

What is the main constituent of

natural gas?

Answer 6

methane

Question 7

Describe petroleum

Answer 7

a mixture of hydrocarbons and its separation into useful fractions by fractional distillation

Question 8

Describe the properties of molecules within a fraction

Answer 8

The less carbon atoms, the lower the boiling point.
As the number of carbon atoms in the hydrocarbon increases:
- the boiling point increases
- the viscosity increases
- the volatility decreases.

Question 9

Name the uses of the fractions

Answer 9

Refinery gas: used as bottled gas for heating and cooking.
Gasoline: used as a fuel for cars.
Naphtha: used as a base for manufacturing many other chemicals, for example, solvents used by painter decorators.
Kerosene: used for jet fuel
Diesel oil: used as a fuel for trucks in diesel engines.
Fuel oil: used as a fuel for ships or heating homes.
Lubricating oil: used for lubricating machinery, and as a base for polishes and waxes.
Bitumen: used for laying tarmac on roads.

Question 10

Describe the concept of homologous series

Answer 10

a ‘family’ of similar compounds with similar chemical properties due to the presence of the same functional group

Question 11

Describe the general characteristics of a homologous series

Answer 11

They have the same structural formula; all come from the same functional group; similar chemical properties.
the alkanes as a homologous series are generally unreactive except for combustion reactions.
The alkenes that have a C=C bond are similar to alkanes except that they are more reactive due to the double bond that can break and open up to join with other atoms.
The alcohols that contain the –OH functional group display the property of miscibility in water, whereas alkanes without the –OH group are not miscible in water. Carboxylic acids with the –COOH readily undergo further chemical reactions and so, for example, can react with alcohols to form esters as we discovered in previous subtopics. The share the similar chemical properties and the same functional groups

Question 12

Describe and identify structural isomerism

Answer 12

when compounds have similar molecular formulas but different arrangement of atoms

Question 13

Describe the properties of alkanes

Answer 13

generally unreactive, except in terms of burning

Question 14

Describe the bonding in alkanes

Answer 14

Alkanes are generally unreactive due to the strength of their covalent bonds. They are often referred to as saturated hydrocarbons. This means that the molecule only has single covalent bonds. They contain only C-C bonds and C-H bonds and each carbon forms 4 covalent bonds.

Question 15

Describe substitution reactions of alkanes with chlorine

Answer 15

In a substitution reaction, an alkane reacts with a halogen to produce a halogenoalkane. This reaction is photochemical, only reacting in the presence of sunlight.

Chlorine molecules (Cl 2 ) are split up and then go on to react with methane in a chain reaction, which produces several different compounds.
The product of this reaction can be chloromethane, dichloromethane, trichloromethane or Tetrachloromethane and hydrochloric acid (HCl) or hydrogen halide.

Question 16

Describe the manufacture of alkenes and of hydrogen by cracking

Answer 16

Cracking is the breaking of long alkane chains (and other more complex organic molecules) into simpler smaller ones through the use of high heat, pressure and catalysts. This process​ ​involved​ ​heating​ ​the​ ​hydrocarbons​ ​to​ ​vaporise​ ​them. The​ ​vapours​ ​are then either​ ​passed​ ​over​ ​a​ ​hot​ ​catalyst​ ​(silica​ ​or​ ​alumina) or mixed​ ​with​ ​steam​ ​and​ ​heated​ ​to​ ​a​ ​very​ ​high​ ​temperature​ ​(temperature in​ ​the​ ​range​ ​of​ ​600-700 ̊C)​ ​so​ ​that​ ​thermal​ ​decomposition​ ​reactions​ ​can occur. The​ ​products​ ​of​ ​cracking​ ​include​ ​shorter​ ​chain​ ​alkanes​ ​and​ ​alkenes​ ​(or​ ​hydrogen)

Question 17

Distinguish between saturated and unsaturated hydrocarbons from molecular structures and by reaction with aqueous bromine

Answer 17

Unsaturated​ ​=​ ​contain​ ​one​ ​or​ ​more​ ​C=C​ ​double​ ​bonds​ ​e.g.​ ​alkenes while saturated​ ​=​ ​contain​ ​no​ ​C=C​ ​double​ ​bonds​ ​e.g.​ ​alkanes. Unsaturated​ ​hydrocarbons​ ​react​ ​with​ ​bromine​ ​in​ ​an​ ​addition​ ​reaction, decolourising​ ​it​ ​as there is no more bromine (​orange​​ ​to​ ​colourless) and saturated​ ​hydrocarbons​ ​do​ ​not​ ​react​ ​with​ ​bromine​ ​and​ ​therefore​ ​the solution​ ​will​​ ​remain​ ​orange

Question 18

Describe the formation of poly(ethene)

Answer 18

an example of addition polymerisation of monomer units

Question 19

Describe the properties of alkenes in terms of addition reactions with bromine, hydrogen and steam

Answer 19

Addition​ ​reactions involve​ ​the​ ​removal​ ​of​ ​C=C​ ​double​ ​bond as the C=C​ ​bond is​ ​very​ ​reactive​ ​and​ ​can​ ​easily​ ​react​ ​to​ ​form​ ​C-C.
- alkene​ ​+​ ​bromine​ ​→​ ​dibromoalkane. E.g.​ ​Ethene​ ​+​ ​bromine​ ​→​ ​1,2-dibromoethane as the double bond breaks.

• alkene​ ​+​ ​steam​ ​→​ ​alcohol, E.g.​ ​Ethene​ ​+​ ​steam​ ​→​ ​ethanol this reaction is called hydrogenation
• alkene​ ​+​ ​hydrogen​ ​→​ ​alkane, E.g.​ ​Ethene​ ​+​ ​hydrogen​ ​→​ ​ethane

Question 20

Describe the manufacture of ethanol by fermentation and by the catalytic addition of steam to ethene

Answer 20

ethene gas obtained from cracking can be further reacted with water in the form of steam to produce ethanol in a process also known as hydration. This reaction is carried out at a temperature of about 550 °C and in the presence of a strong acid, such as sulfuric or phosphoric acid, which acts as a catalyst. Also, fermentation causes ethanol to be produced as yeast respires anaerobically taking glucose to produce ethanol and carbon dioxide.

Question 21

Describe the properties of ethanol in terms of burning

Answer 21

Ethanol is highly flammable and can easily be ignited at temperatures lower than room temperature. It burns readily with oxygen with a clean blue flame and does not produce any soot, releasing a lot of heat energy

Question 22

Name the uses of ethanol

Answer 22

It is used as a solvent for substances that can not dissolve in water and is a solvent for perfume and makeup. Ethanol can also be used as a biofuel for cars.

Question 23

Outline the advantages and disadvantages of the two methods of manufacturing ethanol

Answer 23

Fermentation advantages:
▪ Renewable​ ​raw​ ​materials
▪ Warm,​ ​normal​ ​pressure​ ​(inexpensive)
▪ Little​ ​energy​ ​needed
Fermentation disadvantages:
▪ A​ ​lot​ ​of​ ​workers​ ​needed
▪ Slow
▪ Impure​ ​–​ ​needs​ ​treatment

Steam advantages:
▪ Continuous​ ​process​ ​(runs​ ​all​ ​the​ ​time)
▪ Few​ ​workers​ ​needed
▪ Fast
▪ Pure
Steam disadvantages:
▪ Non-renewable​ ​raw​ ​materials
▪ High​ ​temperature​ ​and​ ​pressure​ ​(expensive)
▪ A​ ​lot​ ​of​ ​energy​ ​needed

Question 24

Describe the properties of aqueous ethanoic acid

Answer 24

It dissolves​ ​in​ ​water​ ​to​ ​produce​ ​an​ ​acidic​ ​solution, has a melting point of 17˚C and a boiling point of approximately 118 °C. It forms ice-like crystals just below 17 °C and in its pure form, is corrosive.

Question 25

Describe the formation of ethanoic acid by the oxidation of ethanol by fermentation and with acidified
potassium manganate(VII)

Answer 25

When ethanoic acid is produced from alcohol as a continuation of the fermentation process, the process happens in the presence of the bacteria acetobacter, which acts as a catalyst. This is acid fermentation. potassium manganate(VIII) is a strong oxidising agent and is used in the presence of sulfuric acid and heat to produce ethanoic acid.

Question 26

Describe ethanoic acid

Answer 26

a typical weak acid, which only partially ionises.

Question 27

Describe the reaction of a carboxylic acid with an alcohol in the presence of a catalyst to give an ester

Answer 27

Esters are produced in the reaction between a carboxylic acid and an alcohol in the presence of a catalyst. E.g ethanoic acid and ethanol with concentrated sulfuric acid as a catalyst. This is called esterification.
- the C–O bond of the OH hydroxyl group in ethanoic acid breaks
- the O–H bond in ethanol breaks
- the two remaining parts from each molecule join together forming a C–O bond for the ester
- a condensation reaction between OH and H occur to produce water.
Name: first part of the alcohol +yl, second part from the acid +oate.

Question 28

polymers

Answer 28

large molecules built up from small units (monomers)

Question 29

Name some typical uses of plastics and of man-made fibres such as nylon and Terylene

Answer 29

Plastics:
o Plastic​ ​bags
o Clingfilm
o Buckets,​ ​other​ ​plastic​ ​tools

Man-made​ ​fibres​ ​such​ ​as​ ​nylon​ ​and​ ​Terylene:
o Drawn​ ​into​ ​very​ ​fine​ ​fibres​ ​and​ ​woven​ ​into​ ​cloth​ ​for​ ​clothing
o Other​ ​natural​ ​fibres​ ​(e.g.​ ​cotton)​ ​can​ ​be​ ​mixed​ ​with​ ​nylon​ ​or​ ​polyester
o fibres​ ​to​ ​make​ ​a​ ​soft​ ​but​ ​hard-wearing​ ​cloth

Question 30

Deduce the structure of the polymer product from a given alkene and vice versa

Answer 30

the​ ​polymer​ ​product​ ​would​ ​be​ ​a​ ​long​ ​chain​ ​of​ ​the​ ​alkene​ ​without​ ​the​ ​C=C​ ​and instead​ ​with​ ​–C​ ​….​ ​C-​ ​at​ ​the​ ​end,​ ​i.e.​ ​open​ ​branches

Question 31

Describe the formation of nylon (a polyamide) and Terylene (a polyester) by condensation polymerisation

Answer 31

In a polyamide reaction for nylon, a carbon bond from the dichloride monomer joins with a nitrogen bond from the diamine monomer to produce a polyamide (nylon) and hydrochloric acid, which is given off, or condensed, from the original monomer units. The reaction will continue with carbon and nitrogen atoms forming bonds with each other alternately. The place where the two functional groups join together is known as the amide linkage.

For terylene, we can see a carbon from the acid join with the oxygen from the diol, ejecting a water molecule in the process. This linkage between the monomer units is a O–C=O bond, known as an ester linkage, and gives this polymer the name polyester. The reaction will continue with carbon atoms bonding to oxygen atoms alternately to build up the polymer chain.

Question 32

What are constituents of food

Answer 32

proteins and carbohydrates

Question 33

Describe proteins in comparison with nylon

Answer 33

possessing the same (amide) linkages as nylon but with different units

Question 34

Describe the structure of proteins

Answer 34

Possessing​ ​the​ ​same​ ​(amide)​ ​linkages​ ​as​ ​nylon​ ​but​ ​with​ ​different​ ​units.

Question 35

Describe the hydrolysis of proteins to amino acids.

Answer 35

For our body to make use of the proteins we eat, they need to be broken down again to amino acids through a process known as hydrolysis . This is the breaking apart of a macromolecule of protein at the amide bond and the addition of water, producing their monomers.

Question 36

Describe complex carbohydrates

Answer 36

A​ ​large​ ​number​ ​of​ ​sugar​ ​units​ ​(diols)​ ​joined​ ​together​ ​by​ ​condensation polymerisation,​ ​e.g.​ ​a​ ​polyester​ ​with​ ​–O-​ ​linkages

Question 37

Describe the hydrolysis of complex carbohydrates (e.g. starch), by acids or enzymes to give simple sugars

Answer 37

when we eat carbohydrates, our bodies need to break them down. This happens by a hydrolysis process using acids (like hydrochloric acid) and enzymes, such as amylase, that are found in our digestive system. This is essentially the reverse of condensation polymerisation and involves the addition of a water molecule by breaking the polymer chain apart at the –C–O–C– bond between the two monomer units. Then they revert to simple sugars

Question 38

Describe the fermentation of simple sugars to produce ethanol (and carbon dioxide).

Answer 38

There are two main intermediary substances formed during the fermentation process, known as pyruvates and acetaldehydes. These two substances are necessary to be created before the final ethanol product is formed

Question 39

Describe, in outline, the usefulness of chromatography in separating and identifying the products of hydrolysis of carbohydrates and proteins

Answer 39

We can use this chromatography effectively to identify, for example, which amino acids are present after a protein chain has been hydrolysed and broken down The R f value for each dot is calculated and is compared to the known R f value for each of the twenty amino acids to identify which amino acids are present. This same principle of molecules with slightly different structures having different affinities for the solution they are placed in during chromatography can be applied for separating and identifying the presence of different types of glucose molecules.
Amino acids and simple sugars are colourless, so a locating agent will be needed to see them.

Question 40

Understand that different polymers have different units and/or different

Answer 40

• Each​ ​polymer​ ​is​ ​made​ ​from​ ​a​ ​certain​ ​monomer​ ​or​ ​monomers,​ ​therefore different​ ​polymers​ ​have​ ​different​ ​units​ ​and/or​ ​different​ ​linkages​ ​(depending​ ​on how​ ​the​ ​monomer(s)​ ​join​ ​up​ ​to​ ​form​ ​the​ ​polymer)
• monomers​ ​can​ ​be​ ​different​ ​lengths​ ​or​ ​can​ ​have​ ​different​ ​groups​ ​attached
• can​ ​have​ ​a​ ​C-C​ ​linkage,​ ​ester​ ​linkage​ ​or​ ​amide​ ​linkage

Question 41

Describe​ ​the​ ​pollution​ ​problems​ ​caused​ ​by​ ​non-biodegradable​ ​plastics

Answer 41

Unable​ ​to​ ​decompose,​ ​because​ ​the​ ​polymers​ ​that​ ​form​ ​these​ ​plastics​ ​are​ ​inert​ ​/ unable​ ​to​ ​react​. Therefore,​ ​microorganisms​ ​and​ ​bacteria​ ​are​ ​unable​ ​to​ ​break them​ ​down. Thus,​ ​the​ ​landfills​ ​are​ ​bad​ ​for​ ​the​ ​environment​ ​as​ ​the​ ​plastics​ ​will​ ​remain in​ ​the​ ​ground,​ ​unable​ ​to​ ​break​ ​down/decompose and they​ ​produce​ ​toxic​ ​gases​ ​when​ ​they​ ​are​ ​burned and carbon dioxide, which​ ​adds​ ​to​ ​global​ ​warming