AQA A Level Chemistry Paper 2 11th June Unofficial Markscheme

Original post by Mcgreggorrrrrrrr

Did it ask for the reagents for the reduction of nitrobenzene???

No, the reactions and conditions one was 1,4-dibromobutane to 1,6-diaminohexane, and the one about reducing nitrobenzene only wanted the equation

Reply 42

homemadeclock

ninhydrin in a fume cupboard?

Original post by Peegs

What was the "How to see the amino acids" question?? Really don't remember this one

Reply 43

Gnuyheatmik

OP

Original post by Peegs

What was the "How to see the amino acids" question?? Really don't remember this one

I can’t remember the exact wording. It’s just how to see the spots on the tlc plate and u needed UV or ninhydrin to make them visible

Reply 44

÷by0

12

Original post by Gnuyheatmik

Tell me your answers so I can update this
I can’t really remember much

Equation 1,6-dibromohexane and excess ammonia

C6H12Br2 + 2 NH3 —-> C6H16N2 + 2 HBr

Nucleophilic substitution skeletal formula with ammonia
Cyclic compound by-product

Equation of ethanoic anhydride (hydrolysis? can't remember)
Forms Ethanoic Acid and Ethanol

Explain the term Complementary in terms of DNA strands
Dna strands have complementary base pairs which are able to form hydrogen bonds between them

Draw hydrogen bonds between the strands
3 bonds between C and G
2 bonds between A and T

Circle the components that make up the nucleotide with cytosine
3 Circles around:
Phosphate group, 2-Deoxyribose, Cytosine

Vegetable Fat Question with CxHy

Initial Rates
3.2 x 10^-4
3.2 x 10^-4
First order
Second order

Bunch of numbers I can remember
1.39
182kg
20000
2.57 x 10^9 Arrhenius
28.5% percentage yield

Diagram Distillation apparatus
Add condenser and thermometer

Hydrolysing proteins
HCl or NaOH debate about his one

Labelling infrared spectrum F,G,E can’t remember the order

6 marker on the 2 different compounds (one was a cyclic ketone the other was an alcohol)
-boiling points
Hydrogen bonding in one of them stronger than dipole forces
-Cnmr
-infrared spec

CO2 how does it cause global warming

Minimum number of amino acids in mixture
7

How to see the amino acids
Fluorescent dye and UV/Ninhydrin

How can they tell if the sample has dried by adding anhydrous calcium something ...

The weird question on Z,Z adding the carbons to a skeletal formula

Name mechanism with benzene
Electrophilic substitution

Reaction with bromine finish off the mechanism
- electrophilic addition forming carbo cation then the second bromine ion adds on. Forms dibromo...

Distinguishing between primary and tertiary alcohol
Add acidified potassium dichromate
Orange --> Green
No Change

Last question about nucleophile not being able to attack an Alkene.
I think it’s either:
C=O is polar so the nucleophile can attack the partially positive carbon. The alkene doesn’t have a C=O group so not polar so can’t be attacked by nucleophile.
OR
The nucleophile repels the double bond in the alkene

Insufficient NaH4B added. Test for aldehyde
Add tollens/fehlings
Silver mirror/red ppt

Molecular/Emperical formula question
C5H8 you had to times by 5 to get a whole number
Structure was C=C-C=C

Formula of the dicarboxylic acid with an Mr of 118
HOOC- (CH2)2 -COOH

Electrospray question can’t remember

Draw two structures for C6H3Br3
One with One peak in C nmr
One with 4 peaks in C nmr
Benzene ring/kekule structure (several correct answers for this one)

Synthesis question
Nitrobenzene to amine equation finish off equation
Add 6[H] to form 2H2O
Reagents are H2 and Ni (more than one correct answer for this one)

Reactants and conditions for something
KCN aqueous ethanolic
Sn/HCl (think there is more than one correct answer for this one)

Think the cyclic compound was from the amino group nucleophilic.sub. on the bromine on the same molecule? Like reacting with its self.

IR was ester at top (bc no OH peak), then alcohol, then, carboxylic acid.

CO2 contributes to global warming as the C=O absorbs IR (heat radiation). Absorbs this energy / retains heat / increases temp of gas (guessing for the second mark).

Rate constant 2.00*10^5 3.s.f. mol-3 dm9 s-1?

I think drying cyclohexane makes the solution turn clear.

Z,Z, skeletal formula has double bond between 9/10 and 12/23. Z same side, so chain curls.

NaBH4 not strong enough reducing agent - polarity in the C=O bond makes it weaker / there are partial charges. C=C bond not polar.

Molecular/emp formula. C5H8, branched monomer, e.g H2C=C(CH3)--CH=CH2

Why does stereoisomerism occurs - double bond cannot rotate, if two different groups are present on each side of the bond then isomerism arises. One cannot rotate into the other.

Draw isomers for golf ball. Don't degrade because no polar bonds, so not susceptible to nucleophillc attack.

How does high-res mass spec differential molecules with Mr = 118? - electro spray adds H+ increasing mass. HOOC=(CH2)2=COOH is -doic so can gain 2 H+ ( each =O > --OH). m/z value becomes 118 2/2 => 60. Others will be m/z = 119/2.

I think C6H3Br3 carbon-NMR was:
C has 2 peaks. => symmetry needed so 1,3,5 - tribromobenzene
D has 4 peaks => 1,2,4 - tribromobenzene (not sure on this one)

For H NMR:
C4H8Br2I had a H2C-CBr2-CH2-CH3 for singlet, triplet and quartet.

Was second two of something, two of another? Think the molecule was symmetrical.

Don't use acyl chlorides because HCl fumes/ reacts violently - irritant / acid raid.

(edited 4 years ago)

Reply 45

jakehill_01

8

Original post by Amaaaaaaaan

Got 19991 for something but 19900 to 3.S.F
183Kg for Paracetemol

it was 20000 to 3.s.f

Reply 46

Original post by Gnuyheatmik

Tell me your answers so I can update this
I can’t really remember much

Equation 1,6-dibromohexane and excess ammonia

C6H12Br2 2 NH3 —-> C6H16N2 2 HBr

Nucleophilic substitution skeletal formula with ammonia
Cyclic compound by-product

Equation of ethanoic anhydride (hydrolysis? can't remember)
Forms Ethanoic Acid and Ethanol

Explain the term Complementary in terms of DNA strands
Dna strands have complementary base pairs which are able to form hydrogen bonds between them

Draw hydrogen bonds between the strands
3 bonds between C and G
2 bonds between A and T

Circle the components that make up the nucleotide with cytosine
3 Circles around:
Phosphate group, 2-Deoxyribose, Cytosine

Vegetable Fat Question with CxHy

Initial Rates
3.2 x 10^-4
3.2 x 10^-4
First order
Second order

Bunch of numbers I can remember
1.39
182kg
20000
2.57 x 10^9 Arrhenius
28.5% percentage yield

Diagram Distillation apparatus
Add condenser and thermometer

Hydrolysing proteins
HCl or NaOH debate about his one

Labelling infrared spectrum F,G,E can’t remember the order

6 marker on the 2 different compounds (one was a cyclic ketone the other was an alcohol)
-boiling points
Hydrogen bonding in one of them stronger than dipole forces
-Cnmr
-infrared spec

CO2 how does it cause global warming

Minimum number of amino acids in mixture
7

How to see the amino acids
Fluorescent dye and UV/Ninhydrin

How can they tell if the sample has dried by adding anhydrous calcium something ...

The weird question on Z,Z adding the carbons to a skeletal formula

Name mechanism with benzene
Electrophilic substitution

Reaction with bromine finish off the mechanism
- electrophilic addition forming carbo cation then the second bromine ion adds on. Forms dibromo...

Distinguishing between primary and tertiary alcohol
Add acidified potassium dichromate
Orange --> Green
No Change

Last question about nucleophile not being able to attack an Alkene.
I think it’s either:
C=O is polar so the nucleophile can attack the partially positive carbon. The alkene doesn’t have a C=O group so not polar so can’t be attacked by nucleophile.
OR
The nucleophile repels the double bond in the alkene

Insufficient NaH4B added. Test for aldehyde
Add tollens/fehlings
Silver mirror/red ppt

Molecular/Emperical formula question
C5H8 you had to times by 5 to get a whole number
Structure was C=C-C=C

Formula of the dicarboxylic acid with an Mr of 118
HOOC- (CH2)2 -COOH

Electrospray question can’t remember

Draw two structures for C6H3Br3
One with One peak in C nmr
One with 4 peaks in C nmr
Benzene ring/kekule structure (several correct answers for this one)

Synthesis question
Nitrobenzene to amine equation finish off equation
Add 6[H] to form 2H2O

Reagents for the reduction of nitrobenzene
Reagents are H2 and Ni (more than one correct answer for this one)

Reagents and conditions for 2 step synthesis to form an amine
KCN aqueous ethanolic
Sn/HCl (think there is more than one correct answer for this one)

The global warming question is because. CO2 cant absorb infrared. So it reflects it back into the atmosphere expressed by the lack of the C-O bond in the infrared

Reply 47

Yeahh I got that too

Original post by jakehill_01

it was 20000 to 3.s.f

Reply 48

A nucleotide is only cytosine you wouldn't circle deoxyribose sugar or the phosphate

Original post by Gnuyheatmik

Tell me your answers so I can update this
I can’t really remember much

Equation 1,6-dibromohexane and excess ammonia

C6H12Br2 2 NH3 —-> C6H16N2 2 HBr

Nucleophilic substitution skeletal formula with ammonia
Cyclic compound by-product

Equation of ethanoic anhydride (hydrolysis? can't remember)
Forms Ethanoic Acid and Ethanol

Explain the term Complementary in terms of DNA strands
Dna strands have complementary base pairs which are able to form hydrogen bonds between them

Draw hydrogen bonds between the strands
3 bonds between C and G
2 bonds between A and T

Circle the components that make up the nucleotide with cytosine
3 Circles around:
Phosphate group, 2-Deoxyribose, Cytosine

Vegetable Fat Question with CxHy

Initial Rates
3.2 x 10^-4
3.2 x 10^-4
First order
Second order

Bunch of numbers I can remember
1.39
182kg
20000
2.57 x 10^9 Arrhenius
28.5% percentage yield

Diagram Distillation apparatus
Add condenser and thermometer

Hydrolysing proteins
HCl or NaOH debate about his one

Labelling infrared spectrum F,G,E can’t remember the order

6 marker on the 2 different compounds (one was a cyclic ketone the other was an alcohol)
-boiling points
Hydrogen bonding in one of them stronger than dipole forces
-Cnmr
-infrared spec

CO2 how does it cause global warming

Minimum number of amino acids in mixture
7

How to see the amino acids
Fluorescent dye and UV/Ninhydrin

How can they tell if the sample has dried by adding anhydrous calcium something ...

The weird question on Z,Z adding the carbons to a skeletal formula

Name mechanism with benzene
Electrophilic substitution

Reaction with bromine finish off the mechanism
- electrophilic addition forming carbo cation then the second bromine ion adds on. Forms dibromo...

Distinguishing between primary and tertiary alcohol
Add acidified potassium dichromate
Orange --> Green
No Change

Last question about nucleophile not being able to attack an Alkene.
I think it’s either:
C=O is polar so the nucleophile can attack the partially positive carbon. The alkene doesn’t have a C=O group so not polar so can’t be attacked by nucleophile.
OR
The nucleophile repels the double bond in the alkene

Insufficient NaH4B added. Test for aldehyde
Add tollens/fehlings
Silver mirror/red ppt

Molecular/Emperical formula question
C5H8 you had to times by 5 to get a whole number
Structure was C=C-C=C

Formula of the dicarboxylic acid with an Mr of 118
HOOC- (CH2)2 -COOH

Electrospray question can’t remember

Draw two structures for C6H3Br3
One with One peak in C nmr
One with 4 peaks in C nmr
Benzene ring/kekule structure (several correct answers for this one)

Synthesis question
Nitrobenzene to amine equation finish off equation
Add 6[H] to form 2H2O

Reagents for the reduction of nitrobenzene
Reagents are H2 and Ni (more than one correct answer for this one)

Reagents and conditions for 2 step synthesis to form an amine
KCN aqueous ethanolic
Sn/HCl (think there is more than one correct answer for this one)

Reply 49

Isn't the finish the diagram picture. A bung and condenser. Because the conical flask Is open so the gas would escape

Original post by Gnuyheatmik

Tell me your answers so I can update this
I can’t really remember much

Equation 1,6-dibromohexane and excess ammonia

C6H12Br2 2 NH3 —-> C6H16N2 2 HBr

Nucleophilic substitution skeletal formula with ammonia
Cyclic compound by-product

Equation of ethanoic anhydride (hydrolysis? can't remember)
Forms Ethanoic Acid and Ethanol

Explain the term Complementary in terms of DNA strands
Dna strands have complementary base pairs which are able to form hydrogen bonds between them

Draw hydrogen bonds between the strands
3 bonds between C and G
2 bonds between A and T

Circle the components that make up the nucleotide with cytosine
3 Circles around:
Phosphate group, 2-Deoxyribose, Cytosine

Vegetable Fat Question with CxHy

Initial Rates
3.2 x 10^-4
3.2 x 10^-4
First order
Second order

Bunch of numbers I can remember
1.39
182kg
20000
2.57 x 10^9 Arrhenius
28.5% percentage yield

Diagram Distillation apparatus
Add condenser and thermometer

Hydrolysing proteins
HCl or NaOH debate about his one

Labelling infrared spectrum F,G,E can’t remember the order

6 marker on the 2 different compounds (one was a cyclic ketone the other was an alcohol)
-boiling points
Hydrogen bonding in one of them stronger than dipole forces
-Cnmr
-infrared spec

CO2 how does it cause global warming

Minimum number of amino acids in mixture
7

How to see the amino acids
Fluorescent dye and UV/Ninhydrin

How can they tell if the sample has dried by adding anhydrous calcium something ...

The weird question on Z,Z adding the carbons to a skeletal formula

Name mechanism with benzene
Electrophilic substitution

Reaction with bromine finish off the mechanism
- electrophilic addition forming carbo cation then the second bromine ion adds on. Forms dibromo...

Distinguishing between primary and tertiary alcohol
Add acidified potassium dichromate
Orange --> Green
No Change

Last question about nucleophile not being able to attack an Alkene.
I think it’s either:
C=O is polar so the nucleophile can attack the partially positive carbon. The alkene doesn’t have a C=O group so not polar so can’t be attacked by nucleophile.
OR
The nucleophile repels the double bond in the alkene

Insufficient NaH4B added. Test for aldehyde
Add tollens/fehlings
Silver mirror/red ppt

Molecular/Emperical formula question
C5H8 you had to times by 5 to get a whole number
Structure was C=C-C=C

Formula of the dicarboxylic acid with an Mr of 118
HOOC- (CH2)2 -COOH

Electrospray question can’t remember

Draw two structures for C6H3Br3
One with One peak in C nmr
One with 4 peaks in C nmr
Benzene ring/kekule structure (several correct answers for this one)

Synthesis question
Nitrobenzene to amine equation finish off equation
Add 6[H] to form 2H2O

Reagents for the reduction of nitrobenzene
Reagents are H2 and Ni (more than one correct answer for this one)

Reagents and conditions for 2 step synthesis to form an amine
KCN aqueous ethanolic
Sn/HCl (think there is more than one correct answer for this one)

Reply 50

jakehill_01

8

nah mate, a nucleotide is the whole thing

Original post by friendjm

A nucleotide is only cytosine you wouldn't circle deoxyribose sugar or the phosphate

Reply 51

kursk1896

Original post by friendjm

A nucleotide is only cytosine you wouldn't circle deoxyribose sugar or the phosphate

nah dude, nucleotide is the whole unit, including the sugar and the phosphate

Reply 52

Joe Furn

8

I think you needed a thermometer aswell

Original post by friendjm

Isn't the finish the diagram picture. A bung and condenser. Because the conical flask Is open so the gas would escape

Reply 53

aselva4crisp9

am i the only one who got 24.8 for the % yield of cyclohexanol... ok yep just me

Reply 54

blueoreo

3

did you do it using mass? I got 28 but I used moles.

Original post by aselva4crisp9

am i the only one who got 24.8 for the % yield of cyclohexanol... ok yep just me

Reply 55

aselva4crisp9

i used the mass, not moles

Original post by blueoreo

did you do it using mass? I got 28 but I used moles.

Reply 56

markscheme20

1

Equation 1,6-dibromohexane and excess ammonia

C6H12Br2 2 NH3 —-> C6H16N2 2 HBr

Nucleophilic substitution skeletal formula with ammonia
Cyclic compound by-product
The NH3 of one end comes around and replaces the Br at the other end

Ester formed:
Ethyl propanoate

Explain the term Complementary
Dna strands have complementary base pair shapes which allow for hydrogen bonds between them

Draw hydrogen bonds between the strands
3 bonds between C and G
2 bonds between A and T

Circle the components that make up the nucleotide with cytosine
3 Circles around:
Phosphate group, 2-Deoxyribose, Cytosine

Vegetable Fat Question with CxHy

Initial Rates
3.2 x 10^-4
3.2 x 10^-4
First order
Second order

Bunch of numbers I can remember
1.39
182kg
20000
2.57 x 10^-8 Arrhenius
28.5% percentage yield

Diagram Distillation apparatus
Add condenser and thermometer
Arrows (water in water out). Not sure if that will be a mark

Hydrolysing proteins
6 moldm^-3 HCl

Labelling infrared spectrum
F,G,E

6 marker on the 2 different compounds (one was a cyclic ketone the other was an alcohol)
-boiling points
Hydrogen bonding in one of them stronger than dipole forces
-Cnmr from data sheet
-infrared spec from data sheet

CO2 how does it cause global warming
It is a greenhouse gas and so absorbs infrared from the sun, keeping it in the atmosphere

Minimum number of amino acids in mixture
7

How to see the amino acids
Fluorescent dye and UV/Ninhydrin
(A locating agent was added)

How can they tell if the sample has dried by adding anhydrous salt
Apparently the salt stops clumping together

The weird question on Z,Z adding the carbons to a skeletal formula
Should have gone to the 14th carbon along the chain
At the Alkene, to show z, the carbon chain should have bent around in a U shape instead of a zig-zag

Name mechanism with benzene
Electrophilic substitution

Reaction with bromine finish off the mechanism
- electrophilic addition forming carbo cation then the second bromine ion adds on. Forms dibromoalkane

Distinguishing between primary and tertiary alcohol
Add acidified potassium dichromate
Orange --> Green
No Change

Last question about nucleophile not being able to attack an Alkene.
I think it’s either:
C=O is polar so the nucleophile can attack the partially positive carbon. The alkene doesn’t have a C=O group so not polar so can’t be attacked by nucleophile.
OR
The nucleophile repels the double bond in the alkene

Insufficient NaH4B added. Test for aldehyde
Add tollens/fehlings
Silver mirror/red ppt

Molecular/Emperical formula question
C5H8 you had to times by 5 to get a whole number
Structure was C=C-C=C

Formula of the dicarboxylic acid with an Mr of 118
HOOC- (CH2)2 -COOH

Explain how high resolution electrospray can be used to differentiate between two compounds with an Mr of 118.
High resolution shows the Mr of a molecule to more decimal places

Draw two structures for C6H3Br3
One with One peak in C nmr
One with 4 peaks in C nmr
Benzene ring/kekule structure (several correct answers for this one)

Synthesis question
Nitrobenzene to amine equation finish off equation
Add 6[H] to form 2H2O

Reagents for the reduction of nitrobenzene
Reagents are HCl and Tin catalyst (more than one correct answer for this one)

Reagents and conditions for 2 step synthesis to form an amine
1. KCN aqueous ethanolic/reflux
2. Hydrogen and nickel catalyst/high temp and pressure

The last mechanism (show the first step)
There should have been a H- ion with a lone pair

Dicarboxylic acid titration with NaOH, find the moles in 250cm^3
Can’t remember but had to divide miles by two because it had two COOH and so was a 2:1 reaction

The other product that could have been made in the amine reaction
It could have undergone further substitution to get a tertiary amine (had to draw it)

Explain why amine is a strong base than ammonia
The alkyl group has a positive inductive effect on the nitrogen atom and hence its lone pair of electrons are more available to accept H+ ions

Reply 57

Edexcel Are mugs

The equation for the di amino became had 4 ammonia and 2 moles of ammonium bromide produced

Original post by markscheme20

Equation 1,6-dibromohexane and excess ammonia

C6H12Br2 2 NH3 —-> C6H16N2 2 HBr

Nucleophilic substitution skeletal formula with ammonia
Cyclic compound by-product
The NH3 of one end comes around and replaces the Br at the other end

Ester formed:
Ethyl propanoate

Explain the term Complementary
Dna strands have complementary base pair shapes which allow for hydrogen bonds between them

Draw hydrogen bonds between the strands
3 bonds between C and G
2 bonds between A and T

Circle the components that make up the nucleotide with cytosine
3 Circles around:
Phosphate group, 2-Deoxyribose, Cytosine

Vegetable Fat Question with CxHy

Initial Rates
3.2 x 10^-4
3.2 x 10^-4
First order
Second order

Bunch of numbers I can remember
1.39
182kg
20000
2.57 x 10^-8 Arrhenius
28.5% percentage yield

Diagram Distillation apparatus
Add condenser and thermometer
Arrows (water in water out). Not sure if that will be a mark

Hydrolysing proteins
6 moldm^-3 HCl

Labelling infrared spectrum
F,G,E

6 marker on the 2 different compounds (one was a cyclic ketone the other was an alcohol)
-boiling points
Hydrogen bonding in one of them stronger than dipole forces
-Cnmr from data sheet
-infrared spec from data sheet

CO2 how does it cause global warming
It is a greenhouse gas and so absorbs infrared from the sun, keeping it in the atmosphere

Minimum number of amino acids in mixture
7

How to see the amino acids
Fluorescent dye and UV/Ninhydrin
(A locating agent was added)

How can they tell if the sample has dried by adding anhydrous salt
Apparently the salt stops clumping together

The weird question on Z,Z adding the carbons to a skeletal formula
Should have gone to the 14th carbon along the chain
At the Alkene, to show z, the carbon chain should have bent around in a U shape instead of a zig-zag

Name mechanism with benzene
Electrophilic substitution

Reaction with bromine finish off the mechanism
- electrophilic addition forming carbo cation then the second bromine ion adds on. Forms dibromoalkane

Distinguishing between primary and tertiary alcohol
Add acidified potassium dichromate
Orange --> Green
No Change

Last question about nucleophile not being able to attack an Alkene.
I think it’s either:
C=O is polar so the nucleophile can attack the partially positive carbon. The alkene doesn’t have a C=O group so not polar so can’t be attacked by nucleophile.
OR
The nucleophile repels the double bond in the alkene

Insufficient NaH4B added. Test for aldehyde
Add tollens/fehlings
Silver mirror/red ppt

Molecular/Emperical formula question
C5H8 you had to times by 5 to get a whole number
Structure was C=C-C=C

Formula of the dicarboxylic acid with an Mr of 118
HOOC- (CH2)2 -COOH

Explain how high resolution electrospray can be used to differentiate between two compounds with an Mr of 118.
High resolution shows the Mr of a molecule to more decimal places

Draw two structures for C6H3Br3
One with One peak in C nmr
One with 4 peaks in C nmr
Benzene ring/kekule structure (several correct answers for this one)

Synthesis question
Nitrobenzene to amine equation finish off equation
Add 6[H] to form 2H2O

Reagents for the reduction of nitrobenzene
Reagents are HCl and Tin catalyst (more than one correct answer for this one)

Reagents and conditions for 2 step synthesis to form an amine
1. KCN aqueous ethanolic/reflux
2. Hydrogen and nickel catalyst/high temp and pressure

The last mechanism (show the first step)
There should have been a H- ion with a lone pair

Dicarboxylic acid titration with NaOH, find the moles in 250cm^3
Can’t remember but had to divide miles by two because it had two COOH and so was a 2:1 reaction

The other product that could have been made in the amine reaction
It could have undergone further substitution to get a tertiary amine (had to draw it)

Explain why amine is a strong base than ammonia
The alkyl group has a positive inductive effect on the nitrogen atom and hence its lone pair of electrons are more available to accept H+ ions

Reply 58

Lucallah