AQA Chemistry 2021 paper 2
LATEST
QA Chemistry 2021 paper 2
AQA Chemistry 2021 paper 2
ALCOHOLS: Primary and secondary alcohols are identified using acidified potassium dichromate. It turns from orange to green if they are present. Tertiary alcohols
are not oxidised and the potassium dichromate remains green.
ALDEHYDES: METHOD 1- Tollens reagent is added to the solution being tested and is warmed gently. If an aldehyde is present, a silver mirror will f orm I the test
tube. If not, the solution will remain colourless. METHOD 2- Fehlings solution is added to the solution being tested and is heated. A brick red precipitate will form if
an aldehyde is present and if not, the solution remains blue and there is no observed change.
ALKENES: Bromine water is used to test unsaturated hydrocarbons. It changes from orange-brown to colourless is a carbon-carbon double bond is present. If not, no
change is observed.
CARBOXYLIC ACID: These compounds react with sodium carbonate as acids, producing co2. This gas can be collected and tested using limewater. This solution will
turn cloudy if the gas is co2.
MASS SPECTROMETRY (HIGH RESOLUTION MASS SPECTROMETRY): Used to identify compounds and determine their molecular formula. High resolution mass spec
is a much more sensitive form of mass spec which allows the Mr of a substance to be determined. Precise atomic masses are given and can be used o calculate the
molecular of the compound being tested.
INFRARED SPECTROSCOPY: Used to determine the functional groups present in organic compounds. The IR radiation is passed through a sample where the different
types of bonds absorb the radiation in different amounts. These varying amounts of absorbances are measured and recorded allowing certain bonds and functional
groups to be identified. A spectrum is produced from the measurements which has characteristic curves for the different functional groups. OH alcohol group peak is
in the range 3230-3550cm-1. OH acid group peak is in the range 2500-3000cm-1. The C=C Unsaturated group peak is in the range of 1620=1680cm-1. The C=O
carbonyl groups peak is in the range 1680-1750cm-1. Each IR spectrum has a fingerprint region to the right-hand side. This contains tiny differences from species to
species which acts as a molecular fingerprint, allowing it to be identified.
CFC’S (OZONE LAYER): IR absorption occurs in the atmosphere with molecules suck as ozone. This causes heat to be trapped within earth’s atmosphere. When
chemicals like CFC;s are released into atmosphere from human activity , this heating is enhanced and leads to global warming. Ozone in the atmosphere absorbs UV
radiation. CFC’s absorb UV radiation, breaking down the carbon-halogen bonds to form free radicals that can catalyse ozone depletion. CFC-free solvents are now
being produced to prevent them entering the atmosphere. This helps minimise Ozone depletion and global warming.
NUCLEOPHILIC SUBSTITUTION: Halogenoalkakes contain polar bonds as the halogens are more electronegative than carbon atoms (electron density is drawn
towards the halogen forming delta+ and delta- regions). Nucleophiles (contain a lone electron pair that is attracted to delta+ regions of molecules. Most common
nucleophiles are CN:- , :NH3, and :OH.(must be shown with the lone pair of electrons and often with a negative sign indicating that they are nucleophiles.
Nucleophilic substitution can be used to show how nucleohiles attack halogenoalkanes and can be used to produce alcohols or amines from halogenoalkanes.
The greater the Mr of the halogen in polar bond, the lower the bond enthalpy (it can be broken easily) therefore rate of reaction for these halogenoalkanes is faster.
NS reactions can only occur for primary and secondary halogenoalkanes.
ELIMINATION: When halogenoalkane is heated to high temp under alcoholic conditions, Elimination occurs. The nucleophile acts as a base and accepts a proton ,
removing a hydrogen atom from the molecule. This results in elimination of the halide too producing a carbon-carbon double bond (an alkene).
CATALYTIC CONVERTORS: Carbon monoxide is toxic gaseous product (dangerous for humans- as it is has no odor or colour) oxides of nitrogen are produced as by-
product of alkane combustion. Both of these products can be removed from the system using catalytic converter. Rhodium Catalyst is used to convert harmful
products into more stable products like CO2 or H20.
This study source was downloaded by 100000831443009 from CourseHero.com on 03-16-2022 08:06:23 GMT -05:00
https://www.coursehero.com/file/99419331/AQA-Chemistry-2021-paper-2odt/
, AQA Chemistry 2021 paper 2
LATEST
QA Chemistry 2021 paper 2
COMBUSTION OF ALKANES: alkanes are good fuels because they release a lot of energy when burned. When sufficient oxygen is present they undergo complete
combustion to produce carbon dioxide and water.
If the oxygen present is insufficient, combustion is incomplete and carbon monoxide is produced alongside water.
ELECTROPHILIC ADDITION (ALKENES): These are electron acceptors and are attracted to areas of high electron density. Most common ones are: HBr,Br2 and H2SO4.
Can be used to form alcohols or halogenoalkanes from alkenes.
ALKENES: Unsaturated hydrocarbons meaning (contain carbon=carbon). In an area of high electron density making it susceptible to attack from electrophiles(species
that are attracted to delta- areas). It consists of a covalent bond and a pie bond.
Bromine water is used to identify the double bond and other unsaturated compounds. Turns the solution from orange-brown to colourless if a double bond is
present.
CARBOCATIONS (ELECTROPHILIC ADDITION): This shows how electrophiles attack double bond in alkenes. When the double bond is broken , a carbocation forms.
This is a carbon atom with only three bonds (has a positive charge). Carbocations have varying stability (tertiary is most stable and primary is least stable) The most
stable carbocation , the more likely it is to form. In addition reactions, multiple products can form but major product will always be the most stable.
DISTILLATION (OXIDATION OF ALCOHOLS): Alcohols can be primary, secondary or tertiary. Primary and secondary alcohols can be oxidised to produce various
products but tertiary alcohols are not easily oxidised.
Primary alcohols can be heated in the presence of acidified potassium dichromate and distilled to produce aldehydes.
When heated further under reflux conditions, primary alcohols oxidise further to produce carboxylic acids.
Secondary alcohols can be oxidised when heated in the presence of acidified potassium dichromate to produce ketones.
This study source was downloaded by 100000831443009 from CourseHero.com on 03-16-2022 08:06:23 GMT -05:00
https://www.coursehero.com/file/99419331/AQA-Chemistry-2021-paper-2odt/
LATEST
QA Chemistry 2021 paper 2
AQA Chemistry 2021 paper 2
ALCOHOLS: Primary and secondary alcohols are identified using acidified potassium dichromate. It turns from orange to green if they are present. Tertiary alcohols
are not oxidised and the potassium dichromate remains green.
ALDEHYDES: METHOD 1- Tollens reagent is added to the solution being tested and is warmed gently. If an aldehyde is present, a silver mirror will f orm I the test
tube. If not, the solution will remain colourless. METHOD 2- Fehlings solution is added to the solution being tested and is heated. A brick red precipitate will form if
an aldehyde is present and if not, the solution remains blue and there is no observed change.
ALKENES: Bromine water is used to test unsaturated hydrocarbons. It changes from orange-brown to colourless is a carbon-carbon double bond is present. If not, no
change is observed.
CARBOXYLIC ACID: These compounds react with sodium carbonate as acids, producing co2. This gas can be collected and tested using limewater. This solution will
turn cloudy if the gas is co2.
MASS SPECTROMETRY (HIGH RESOLUTION MASS SPECTROMETRY): Used to identify compounds and determine their molecular formula. High resolution mass spec
is a much more sensitive form of mass spec which allows the Mr of a substance to be determined. Precise atomic masses are given and can be used o calculate the
molecular of the compound being tested.
INFRARED SPECTROSCOPY: Used to determine the functional groups present in organic compounds. The IR radiation is passed through a sample where the different
types of bonds absorb the radiation in different amounts. These varying amounts of absorbances are measured and recorded allowing certain bonds and functional
groups to be identified. A spectrum is produced from the measurements which has characteristic curves for the different functional groups. OH alcohol group peak is
in the range 3230-3550cm-1. OH acid group peak is in the range 2500-3000cm-1. The C=C Unsaturated group peak is in the range of 1620=1680cm-1. The C=O
carbonyl groups peak is in the range 1680-1750cm-1. Each IR spectrum has a fingerprint region to the right-hand side. This contains tiny differences from species to
species which acts as a molecular fingerprint, allowing it to be identified.
CFC’S (OZONE LAYER): IR absorption occurs in the atmosphere with molecules suck as ozone. This causes heat to be trapped within earth’s atmosphere. When
chemicals like CFC;s are released into atmosphere from human activity , this heating is enhanced and leads to global warming. Ozone in the atmosphere absorbs UV
radiation. CFC’s absorb UV radiation, breaking down the carbon-halogen bonds to form free radicals that can catalyse ozone depletion. CFC-free solvents are now
being produced to prevent them entering the atmosphere. This helps minimise Ozone depletion and global warming.
NUCLEOPHILIC SUBSTITUTION: Halogenoalkakes contain polar bonds as the halogens are more electronegative than carbon atoms (electron density is drawn
towards the halogen forming delta+ and delta- regions). Nucleophiles (contain a lone electron pair that is attracted to delta+ regions of molecules. Most common
nucleophiles are CN:- , :NH3, and :OH.(must be shown with the lone pair of electrons and often with a negative sign indicating that they are nucleophiles.
Nucleophilic substitution can be used to show how nucleohiles attack halogenoalkanes and can be used to produce alcohols or amines from halogenoalkanes.
The greater the Mr of the halogen in polar bond, the lower the bond enthalpy (it can be broken easily) therefore rate of reaction for these halogenoalkanes is faster.
NS reactions can only occur for primary and secondary halogenoalkanes.
ELIMINATION: When halogenoalkane is heated to high temp under alcoholic conditions, Elimination occurs. The nucleophile acts as a base and accepts a proton ,
removing a hydrogen atom from the molecule. This results in elimination of the halide too producing a carbon-carbon double bond (an alkene).
CATALYTIC CONVERTORS: Carbon monoxide is toxic gaseous product (dangerous for humans- as it is has no odor or colour) oxides of nitrogen are produced as by-
product of alkane combustion. Both of these products can be removed from the system using catalytic converter. Rhodium Catalyst is used to convert harmful
products into more stable products like CO2 or H20.
This study source was downloaded by 100000831443009 from CourseHero.com on 03-16-2022 08:06:23 GMT -05:00
https://www.coursehero.com/file/99419331/AQA-Chemistry-2021-paper-2odt/
, AQA Chemistry 2021 paper 2
LATEST
QA Chemistry 2021 paper 2
COMBUSTION OF ALKANES: alkanes are good fuels because they release a lot of energy when burned. When sufficient oxygen is present they undergo complete
combustion to produce carbon dioxide and water.
If the oxygen present is insufficient, combustion is incomplete and carbon monoxide is produced alongside water.
ELECTROPHILIC ADDITION (ALKENES): These are electron acceptors and are attracted to areas of high electron density. Most common ones are: HBr,Br2 and H2SO4.
Can be used to form alcohols or halogenoalkanes from alkenes.
ALKENES: Unsaturated hydrocarbons meaning (contain carbon=carbon). In an area of high electron density making it susceptible to attack from electrophiles(species
that are attracted to delta- areas). It consists of a covalent bond and a pie bond.
Bromine water is used to identify the double bond and other unsaturated compounds. Turns the solution from orange-brown to colourless if a double bond is
present.
CARBOCATIONS (ELECTROPHILIC ADDITION): This shows how electrophiles attack double bond in alkenes. When the double bond is broken , a carbocation forms.
This is a carbon atom with only three bonds (has a positive charge). Carbocations have varying stability (tertiary is most stable and primary is least stable) The most
stable carbocation , the more likely it is to form. In addition reactions, multiple products can form but major product will always be the most stable.
DISTILLATION (OXIDATION OF ALCOHOLS): Alcohols can be primary, secondary or tertiary. Primary and secondary alcohols can be oxidised to produce various
products but tertiary alcohols are not easily oxidised.
Primary alcohols can be heated in the presence of acidified potassium dichromate and distilled to produce aldehydes.
When heated further under reflux conditions, primary alcohols oxidise further to produce carboxylic acids.
Secondary alcohols can be oxidised when heated in the presence of acidified potassium dichromate to produce ketones.
This study source was downloaded by 100000831443009 from CourseHero.com on 03-16-2022 08:06:23 GMT -05:00
https://www.coursehero.com/file/99419331/AQA-Chemistry-2021-paper-2odt/
