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Chemistry Paper 2 > Organic Chemistry > Flashcards

Organic Chemistry Flashcards

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1
Q

Describe what is Meant by a Hydrocarbon

A

-Hydrocarbons are compounds made of hydrogen and carbon only.

-They are used as plastics, including polyester, and as fuels, including petrol and diesel.

-Only a small percentage is used for chemical synthesis.

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2
Q

Describe how Crude Oil is Formed

A

-The remains of ancient biomass of plankton fall to the bottom of the sea.

-It is covered in layers of sediment.

-Over millions of years, the pressure and temperature greatly increases.

-The high pressure and temperature cause crude oil to be formed.

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3
Q

Describe how Coal is Formed

A

-The ancient biomass of trees die and decay.

-It is covered in layers of sediment.

-Over millions of years, the pressure and temperature greatly increases.

-The high pressure and temperature cause crude oil to be formed.

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4
Q

Describe what is Meant by an Alkane

A

-Alkanes are the simplest type of hydrocarbon.

-They are all saturated (each carbon forms four single covalent bonds).

-The general formula for alkanes is CnH2n+2.

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5
Q

Describe the First Four Alkanes

A

-Methane (CH4) has one carbon.

-Ethane (C2H6) has two carbons.

-Propane (C3H8) has three carbons.

-Butane (C4H10) has four carbons.

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6
Q

Describe the Trend in Viscosity in Hydrocarbons

A

As the chain length increases, it becomes more viscous (harder to pour).

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7
Q

Describe the Trend in Flammability in Hydrocarbons

A

As the chain length increases, it becomes less flammable.

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8
Q

Describe the Trend in Volatility in Hydrocarbons

A

As the chain length increases, it becomes less volatile (harder to become a gas).

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9
Q

Describe the Trend in Boiling Points in Hydrocarbons

A

As the chain length increases, the boiling point increases.

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10
Q

Explain why the Boiling Point of Hydrocarbons Increases as the Chain Gets Longer

A

-As the chain length increases, the intermolecular forces of attraction get stronger.

-Therefore, more energy is needed to overcome these forces so the boiling point increases.

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11
Q

Describe the Trend in Colour in Hydrocarbons

A

As the chain length increases, the chains become darker in colour.

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12
Q

Describe what is Meant by Combustion

A

Combustion involves burning in the presence of oxygen.

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13
Q

Describe the Complete Combustion of Hydrocarbons

A

-Complete combustion takes place when there is enough oxygen present.

-Complete combustion produces water and carbon dioxide.

Hydrocarbon + Oxygen → Carbon Dioxide + Water

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14
Q

Describe the Incomplete Combustion of Hydrocarbons

A

-Incomplete combustion takes place when there is not enough oxygen present.

-Incomplete combustion produces water and carbon monoxide or soot.

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15
Q

Explain why the Combustion of Hydrocarbons is an Example of a Redox Reaction

A

-The carbon and hydrogen atoms both gain oxygen (and lose electrons) so they are oxidised.

-The oxygen (from the air) gains electrons so is reduced.

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16
Q

Describe how Fractional Distillation Separates the Hydrocarbon Chains in Crude Oil

A

-Fractional distillation works by separating hydrocarbons with different chain lengths based on their boiling points.

-The longer the chain, the stronger the attraction between molecules.

-The fractional distillation column has a temperature gradient, it is cooler at the top and hotter at the bottom.

-The hydrocarbons are heated until they are gases.

-The vapours rise up the column until they reach the temperature of their boiling point.

-At this point, they condense into liquids and are piped off and used, mainly as fuels.

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17
Q

State Different Fractions by Decreasing Boiling Point

A

Highest Boiling Point: Bitumen

-Heavy Fuel Oil
-Diesel Oil
-Kerosene
-Petrol

Lowest Boiling Point: Liquified Petroleum Gas

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18
Q

State the Uses of Crude Oil

A

-Oil provides the fuel for most transport.

-Some of the hydrocarbons from crude oil are used as feedstock.

-This is to make new compounds for use in things like polymers, solvents, lubricants and detergents.

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19
Q

Explain why Short Chain Hydrocarbons are Removed From the Fractional Distillation Column as Gases Rather than Liquids

A

-Very short chain hydrocarbons have very low boiling points.

-The top of the fractionating column is not cool enough for these hydrocarbons to condense.

-This means that very short chain hydrocarbons are removed as gases.

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20
Q

Describe what is Meant by Cracking

A

Cracking is the process of turning long chain hydrocarbons (high supply, low demand) into shorter hydrocarbons (low supply, high demand).

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21
Q

Explain why Long Chain Hydrocarbons are Cracked.

A

-Long chain hydrocarbons are cracked because long chain hydrocarbons are less flammable than short chain hydrocarbons.

-This means that long chain hydrocarbons are not very useful as fuels.

-By cracking them, long chain hydrocarbons are converted into short chain hydrocarbons.

-These are more flammable and are therefore more useful as fuels.

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22
Q

Describe the Process of Cracking

A

-Heat the hydrocarbons to vaporise.

-Pass them over a hot catalyst (catalytic cracking).

-OR, Heat them to a high temperature with steam (thermal cracking).

-Thermal decomposition then occurs.

-Shorter alkanes and alkenes are produced. Alkenes may be used to make other molecules such as polymers.

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23
Q

Describe how to Test for the Presence of Alkanes and Alkenes

A

-To test for the presence of alkanes and alkenes, add bromine water.

-If an alkane is present, the substance will remain the colour of bromine (orange).

-If an alkene is present, the substance will turn colourless.

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24
Q

Explain why Bromine Turns Colourless When Added to an Alkene

A

-When bromine water is added to an alkane, no reaction will happen as the alkane is saturated so it will remain orange.

-When bromine water is added to an alkene, the bromine will add across the double bond, making a colourless dibromo compound- so the bromine water is decolourised.

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25
Q

Describe what is Meant by an Alkene

A

An alkene is an unsaturated hydrocarbon (has a carbon to carbon double bond) with the general formula CnH2n.

-Alkenes have a double covalent bond between two carbon atoms.

-Because methane only has a single carbon atom, there cannot be an alkene based on methane.

26
Q

Describe the Reaction of Alkenes

A

-Alkenes undergo addition reactions because the carbon to carbon double bond opens up to form a carbon to carbon single bond.

-This allows a new covalent bond to be formed on each carbon.

-There are no additional products formed so there is a 100% atom economy.

27
Q

Explain why Alkenes Produce a Smoky Flame

A

-When alkenes combust, they often undergo incomplete combustion.

-This means that as well as carbon dioxide and water, carbon particles are also produced.

-Carbon particles make the flame appear smoky.

28
Q

Describe the Reaction of Alkenes With Hydrogen

A

-Reacting alkenes with hydrogen is called hydrogenation.

-The conditions for this reaction require a nickel catalyst and a temperature of around 150℃.

-Hydrogenation is useful because it can be used to turn unsaturated fat into saturated fat.

-It is also useful because ‘Hardening’ reactions can turn oil into margarine.

29
Q

Describe the Reaction of Alkenes With Steam

A

-Reacting alkenes with steam is called hydration.

-The conditions for this reaction are 300℃ and 70 atmospheres pressure. The catalyst is phosphoric
acid.

-Water is added across the double bond and an alcohol is formed.

30
Q

Explain why Hydration Takes Place at High Pressure

A

-Le Chatelier’s principle states that if a system is at equilibrium and a change is made to the conditions, then the system responds to counteract the change.

-In the hydration reaction, we have two reactant molecules (the alkene and the water) and one product molecule (the alcohol). All of the molecules are gases.

-If we increase the pressure of the system, the position of the equilibrium will shift to the side with the smaller number of molecules.

-In this case, if we increase the pressure, the position of the equilibrium shifts to the right so we make more product.

31
Q

Describe the Reaction of Alkenes With Halogens

A

-Reacting alkenes with halogens is called halogenation.

-The molecules formed are saturated, with the carbons from the double bond each becoming bonded to a halogen atom.

32
Q

Compare Ethane to Ethene

A

-Both are hydrocarbons

-Both contain two carbon atoms per molecule

-Ethane contains six hydrogen atoms per molecule but ethene contains four hydrogen atoms per molecule

-Both have covalent bonds

-Ethane contains a single C—C bond but ethene contains a double bond

-Both contain C—H bonds

-Both small molecules

33
Q

Describe what is Meant by a Functional Group and a Homologous Series

A

-A homologous series is a family of compounds with the same functional group and increasing length chain of carbons.

-A functional group is part of a molecule with characteristic reactions e.g. C=C is the functional group in the alkene homologous series.

34
Q

Explain why Different Alkenes React in a Similar Way

A

-All of the alkenes have the same functional group.

-The functional group determines how a molecule reacts.

-Because the alkenes all have the same functional group, they all react in a similar way.

35
Q

State the Main Uses of Alcohols

A

-Alcohols are mainly used as fuels, solvents and in alcoholic drinks (ethanol).

-The functional group of an alcohol is O-H

36
Q

Describe the Properties of Alcohols

A

-All alcohols are soluble (dissolve in) water.

-All alcohols are neutral (have pH 7).

-All alcohols are very flammable (therefore we can combust them). When alcohols are completely combusted, carbon dioxide and water are the products.

-Alcohols are highly flammable because they already contain oxygen so require less to combust.

37
Q

Describe the Reaction of Alcohols with Potassium Dichromate Solution

A

-There is a colour change from orange to green.

-It turns an alcohol into a carboxylic acid.

-This is an oxidation process.

38
Q

Describe the Reactions of Alcohols with Group 1 Metals

A

-The substance fizzes.

-Hydrogen gas is produced.

39
Q

Explain why the Ethanol Made Through the Industrial Process Cannot be Drank

A

-The industrial process to create ethanol produces 100% atom economy.

-However, the ethanol produced is difficult to purify so cannot be drank.

40
Q

Describe the Process of Making Ethanol by Fermentation

A

-Boil water (to kill bacteria).

-Add sugar (food for the yeast).

-Allow to cool (over 50℃ will kill the yeast)

-Add yeast (this is the organism with the enzymes to make ethanol).

-Leave to respire (anaerobic respiration).

41
Q

State the Conditions Required to Produce Ethanol From a Sugar Solution

A

-This process is called fermentation.

-Yeast needs to be added.

-Warm and anaerobic conditions are needed.

42
Q

State the Advantages of Hydration

A

-The reaction produces a high yield of ethanol.

-The reaction can produce any alcohol, not just ethanol.

43
Q

State the Disadvantages of Hydration

A

-This reaction requires a high temperature, needing a lot of energy.

-The starting material comes from crude oil which is non renewable.

44
Q

State the Advantages of Fermentation

A

-This reaction requires a low temperature so not much energy is needed.

-The starting material comes from plants and is therefore renewable.

45
Q

State the Disadvantages of Fermentation

A

-This reaction can only be used to make the alcohol ethanol.

-This makes an aqueous solution of ethanol. Distilling the ethanol requires energy.

46
Q

Explain why the Reaction to Produce Carboxylic Acid is an Example of Oxidation

A

-Turning alcohol into a carboxylic acid is an example of oxidation because there is a gain of oxygen.

-An alcohol contains one oxygen whereas a carboxylic acid contains two.

-The functional group of carboxylic acids is H-O-C=O

47
Q

Describe the Properties of Carboxylic Acids

A

-Carboxylic acids are weak acids. This means they partially ionise when dissolved in water.

-Because carboxylic acids are weak acids, they have a relatively low concentration of H+ which means that they have a relatively high pH value compared to strong acids.

48
Q

Describe the Reactions of Carboxylic Acids

A

-A carboxylic acid reacts with a metal to produce a salt and hydrogen.

-A carboxylic acid reacts with a metal carbonate to produce a salt and water and carbon dioxide.

-A carboxylic acid reacts with alcohols to make an ester.

49
Q

Describe how Esters are Made

A

-A carboxylic acid reacts with an alcohol via a condensation reaction to make an ester and water.

-It is a reversible reaction. An acid catalyst is usually used (e.g. sulfuric acid).

-The functional group of an ester is O=C-O

50
Q

Describe the Uses of Esters

A

-Esters have strong, sweet smells. This means they are often used in food flavourings and perfumes.

-They are also good at dissolving organic compounds so are often used as solvents.

51
Q

Describe how the Yield of Ethyl Ethanoate can be Increased

A

-Le Chatelier’s principle states that if a system is at equilibrium and a change is made to the conditions, then the system responds to counteract the change.

-We can force the position of the equilibrium to the right (products) by increasing the concentration of the reactants

-This means the system makes more product thereby lowering the concentration of the reactant.

52
Q

Describe what is Meant by Polymerisation

A

-Polymerisation is the joining of many repeated units (monomers) to make long chain molecules (polymers).

-Plastics are an example of polymers.

53
Q

Describe Addition Polymerisation

A

-In addition polymerisation, the monomer needs a carbon to carbon double bond. Therefore, alkenes are used.

-The long chain has the same atoms as the monomer because no other molecule is formed in the reaction.

-There is 100% atom economy.

-The double bond in the monomer breaks to add other monomers.

54
Q

Describe Condensation Polymerisation

A

-Condensation polymerisation involves monomers which contain different functional groups.

-The monomers react together and bonds form between them, making polymer chains.

-Condensation polymers are made from diols and dicarboxylic acids.

-For each new bond that forms, a small molecule (e.g. water) is lost.

55
Q

Explain why Polyester Melts When Heated

A

-Polyester is thermosoftening.

-It has no cross links.

-This means it can be reshaped into new products.

56
Q

Compare Addition Polymerisation to Condensation Polymerisation

A

Addition Polymerisation:

-1 monomer is used
-Formed from alkenes
-No co-products are produced
-100% atom economy

Condensation Polymerisation:

-Formed from 2 monomers
-Formed from a diol and a dicarboxylic acid
-Water is produced
-The atom economy is less than 100%

57
Q

Describe the Monomers Used to Make Polypeptides (Proteins)

A

-The monomer used to make a polypeptide is an amino acid.

-An amino acid contains two different functional groups- a basic amino group (NH2) and an acidic carboxyl group (COOH).

-The group underneath the carbon makes each amino acid unique.

-Polypeptides are made by condensation polymerisation (so water is also made).

58
Q

Describe the Monomers Used to Make Polysaccharides

A

-The monomer used to make a polysaccharide is glucose. Examples include starch and cellulose.

-Starch is a linear form of glucose whereas cellulose is a branched form of glucose.

-Polysaccharides are made by condensation polymerisation (so water is also made).

59
Q

Describe the Monomers Which Make up DNA

A

-DNA (Deoxyribonucleic Acid) is a polynucleotide made from nucleotide monomers.

-A nucleotide is made up of a phosphate group, a sugar (Ribose) and a base.

-DNA exists as two polynucleotide chains joined together to make a double helix.

60
Q

Describe the Shape and Structure of DNA

A

-There are two polymer chains.

-These are made up of four different monomers.

-It is shaped as a double helix.

Chemistry Paper 2 (5 decks)

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