UNOFFICIAL MARK SCHEME - AQA AS Chemistry 13/01/2012 (UPDATED)

Drink some water. and breathe.
Why you taking my UNOFFICIAL mark scheme to heart?
If you read the mark scheme, you would of seen that I added about 5 hours ago a alternative view to that answer stating that they may of asked for moles and therefore answer was 0.0260.

& If you read my post you would of saw that I put the same answer as you lot, so before you start virtually attacking people. Take a chill pill. I mean literally take something... you're mental.

Some crazy lady if you read the post above, started attacking me as if my unofficial mark scheme is going to determine her grade, Lady Im not a secret AQA examiner Im just a girl with a memory

Drink some water. and breathe.
Why you taking my UNOFFICIAL mark scheme to heart?
If you read the mark scheme, you would of seen that I added about 5 hours ago a alternative view to that answer stating that they may of asked for moles and therefore answer was 0.0260.

& If you read my post you would of saw that I put the same answer as you lot, so before you start virtually attacking people. Take a chill pill. I mean literally take something... you're mental.



They asked for volume on the one where you a 3:8 ratio,
then asked for moles for the ideal gas equation one.

Some crazy lady if you read the post above, started attacking me as if my unofficial mark scheme is going to determine her grade, Lady Im not a secret AQA examiner Im just a girl with a memory

Anywho let me add the octane question

Solid B.

You sure? How's it been for the last few year's for the Jan exam's? Was hoping for an A , but that's way out now :/.
But a 'B' I would be REALLY happy with, considering how bad I had done.

This is a prediction I have adapted and changed, so don't panic if your questions vary and questions are not in right order but I ensure you the marks are all there, if not this is all from memory remember, play nice and enjoy
[*] - Indicated my side comments

1) State this bond & How it is formed;
Covalent bond (1 mark) Shared pair of electrons *between non-metal atoms (1 mark)

2) Shapes of Molecules questions;
- BF3 (should resemble a trigonal planar shape OR t-shaped (since a previous mark scheme allows both), incorporated with two lone pairs) (1 mark)
- Angle *There is debate with this so these are what most people have said
- 120 (115-120) OR 90 (85-90) (1 mark)

- BrF4 (Should resemble Square Planar Shape, incorporated with two lone pairs) (1 mark)
- Angle: 90 (1 mark)

3) Why does KbrF4 have a higher melting point?, explain in terms of bonding.
*Therefore including structure wouldn’t gain/loose any marks if added
- Ionic bonding (1 mark) electrostatic forces/attraction between K+ and Br- oppositely charged ions (1 marks) require a lot of energy to overcome (1 mark)

4) Volume question, to be converted from cm3 to m3 s
PV = nRT or V = nRT/P (1 mark)
Correctly changing 101kpa to 101,000 pa & cm3 to m3 by x by (10 to the power of -6) (1 mark)
Answer is 0.0260 (1 marks)
*If you got 0.0175, or something like that it is because you forgot to convert cm3 tom3 or didnt convert it properly but all is not lost, since you get marks for working out


. Calculation questions for Volume of Nitric acid = 0.0524 dm3

*my working out:
8.14 / 207.2 = 0.0393
Then to get moles of n02 you times by 8/3 (due to 3:8 ratio)
so 0.0393 x 8/3 = 0.1048 moles of n02 ( 2 marks - for correct working out)

then 0.1048/ 2.00 (conc) to get volumes = 0.0524 dm3 (1 mark for correct answer and unit)

5) Which element in group 2, has the largest atomic radius?
- Lithium (1 mark)
*I assure you, they did not ask why or why there was a trend, ignore any unofficial mark scheme which say so.

6) How would HCL be labelled?
Irritant/Corrosive/Toxic (1 mark)

7) Electron Configuration; 1s2 2s2 2p6
. (N) 3- (1 mark)
. (F) - (1 mark)

*I also included the proton number/atomic number, if you also did so I highly doubt they will penalise marks for addition information, as long as it does not contradict.

. Why does Fluorine have a low melting Point?
Simple Molecular ( 1 mark)
Weak van de Waals forces between molecules ( 1 mark)


8).Name/State Formulae for Lithium Nitride
Li3N (1 mark)

. Calcium Nitride Empirical Formulae
Correctly stating percentage of Nitrogen (1 mark)
Correct method used ( 1 mark)
Ca3n2 (1 mark)

9) Balance Equation for Lead Nitrate
2___ + 2___ -----> 4___ + 1___
* You did not need to include 1 in front of the 02 at the end as this goes without saying.

10) Sulphur Compounds impact on Environment?
- (Contributed to) Acid Rain (1 mark)

11) Equation to show how CO & NO is removed in a Catalytic Converter
2NO + 2CO -> N2 + 2CO2 ( 1 mark)

12) Equation to show how Si3N4 is formed (1 mark)

3Si + 2N2 -> 3SiN4
OR
1/5 Si2+ N4 --> Si3N4
*There is debate in this however multiples are definitely allowed.


13) Atom Economy Question
Correct method (2 marks)
Correct Answer 76.4% (1 mark)
* Cant remember to what decimal place but it 76.??

14) Why does Carbon have a high melting point?
Macromolecular (1 mark)
Each carbon is covalently bonded to four other carbons (making a tetrahedral shake), networking throughout structure (1 mark)
Strong Covalent bonds ( 1 mark)
Alot of energy is required to overcome/break bonds (1 mark)

15) Completing Graph for Nitrogen
Nitrogen should be plotted with an X, lower than all other elements but NOT on 0.
( 1 mark)

16) What raw material is Hexane Obtained from?
Crude Oil ( 1 mark)

17)
. What substance/material would be used to remove Sulphur
CaO (Calcium Oxide) or CaCO3 (Limstone) ( 1 mark)
. Why is this used?
If you used CaO - It neutralised acid in Sulphur impurity (there is debate for this, I didnt personally use Ca0 so cannot give judgement) (1 mark)
. If used CaCO3 - Limestone can be easily accessed/high in abundance/ there is high supply (1 mark)

18) Draw how H-F molecules interact..
Partial Charges correctly indicated (1 mark)
3 Lone pairs of Fluoride ( 1 mark)
Hydrogen Bond (- - - -) Between Delta Plus H and Fluoride lone pair of a different molecules ( 1 mark)

19) Which type of Cracking produces high % of Alkenes?
- Thermal Cracking ( 1 mark)
State conditions required
- High Temperate and Pressure ( 1 mark)
*You could also gain these marks if you said the actual temperature and pressure required

20) State why Zeolite/Catalyst is used in Catalytic converters
- (Extremely) Large surface area for reaction to take place (1 mark)

21) How many isomers does Hexane have
5 (1 mark)

22) Name the Compound shown
2,2-dichloro-3-methlypentane

.Type of Isomer shown?
Chain Isomerism/Isomer ( 1 mark)

23) Empirical forum ale for compound
C3H6CL (1 mark)

24) How is Krypton Ionised
Electron Gun (1 mark)
bombards/hits Krpton Sample ( 1 mark)
Knocking off electrons forming possitive ions/1+ ions/2+ions ( 1 marks)

25) Ar of Krpton
For correct method (2 marks)
Correct answer to one decimal place 84.0 (1 mark)

. Give reasons why your Ar is different to that of the periodic table (1 mark)
*Again there is debate; so these are the 2 most logical answers people gave
- Mass Spectrometer used for Ar in Periodic table was of a higher resolution than that given in the table therefore answer is more precise/accurate
OR
- Fragments may of fallen off before ions reached detector

(The reason I havent included the meteorite answers because Krpton is the same whatever planet, adding meteorite was just a way of applying knowledge to real-life situations it didn't play any real part in the question for example "Sanjeev and Alice did an experiment" you wouldnt say Sanjeev is more reliable simple because he a boy?, the fact the krpton was apart of the meteorite was a decoy it played no part.)

26) Equation for 1st IE of Krypton.

Kr(g) + e- -> Kr+(g) + 2e-

Or

Kr(g) -> Kr+(g) + e-

For correct state symbols (1 mark)
for Correct equation (1 mark)

27) Explain peak at 42
- (When Krpton sample ionised) a 2+ ion charge/double charged ion was created ( 1 mark)

-

27) Which element deviates from Period 2, general trend, from Li to N
Boron (1 mark)
*If you said Oxygen this would be wrong since they've given you a boundary of from Lithium to Nitrogen

.Explain why
Outer electron is 2p Orbital, Higher energy level than Be in 2s ( 1 mark)
More shielding (as more inner main energy shells) (1 mark)

28) Processed used to obtain Hexane from Crude Oil
Fractional Distillation ( 1 mark)

29) Why it is not possible to get pure N0 on its own? (1 mark)
*There is debate with this answer; I have been suggested the most and make the most logical sense

- NO reacts with water (vapour) in air to form H2N03 (Nitric Acid)
OR
- NO reacts with air to form Nitrogen Dioxide?

(- The reason why 'N0 escpaing into air' wont be accepted is because, you havent explained how that makes it impure? If the question was why can N0 not be 100% obtained/collected which is the next question then that answer would would but its talking about purity.)

. Why is it not possible to get 100% yield of N0 (1 mark)
- Not high enough Temperature/Pressure for Lead Nitrate to completely decompose
OR
- N0 make escape into air, due to being a gas

There was also an equation for write equation for incomplete/complete combustion of an Octane
(cant remember)
but this was (1 mark)

Surely for 29) it would be because NO(g) wasnt the only product in a gaseous state as O2(g) was produced aswell? so it would be hard to separate them to form pure NO

What grade would be 38-42?

are you sure there was 5 isomers of hexane? im sure you're right, but I thought it was 3?

Surely for 29) it would be because NO(g) wasnt the only product in a gaseous state as O2(g) was produced aswell? so it would be hard to separate them to form pure NO

Surely for 29) it would be because NO(g) wasnt the only product in a gaseous state as O2(g) was produced aswell? so it would be hard to separate them to form pure NO

6) How would HCL be labelled?
Irritant/Corrosive/Toxic (1 mark)

3) Why does KbrF4 have a higher melting point?, explain in terms of bonding.
*Therefore including structure wouldn’t gain/loose any marks if added
- Ionic bonding (1 mark) electrostatic forces/attraction between K+ and Br- oppositely charged ions (1 marks) require a lot of energy to overcome (1 mark)


14) Why does Carbon have a high melting point?
Macromolecular (1 mark)
Each carbon is covalently bonded to four other carbons (making a tetrahedral shake), networking throughout structure (1 mark)
Strong Covalent bonds ( 1 mark)
Alot of energy is required to overcome/break bonds (1 mark)

12) Equation to show how Si3N4 is formed (1 mark)
3Si + 2N2 -> 3SiN4
OR
1/5 Si2+ N4 --> Si3N4
*There is debate in this however multiples are definitely allowed.

14) Why does Carbon have a high melting point?
Macromolecular (1 mark)
Each carbon is covalently bonded to four other carbons (making a tetrahedral shake), networking throughout structure (1 mark)
Strong Covalent bonds ( 1 mark)
Alot of energy is required to overcome/break bonds (1 mark)

20) State why Zeolite/Catalyst is used in Catalytic converters
- (Extremely) Large surface area for reaction to take place (1 mark)

24) How is Krypton Ionised
Electron Gun (1 mark)
bombards/hits Krpton Sample ( 1 mark)
Knocking off electrons forming possitive ions/1+ ions/2+ions ( 1 marks)

. Give reasons why your Ar is different to that of the periodic table (1 mark)
*Again there is debate; so these are the 2 most logical answers people gave
- Mass Spectrometer used for Ar in Periodic table was of a higher resolution than that given in the table therefore answer is more precise/accurate
OR
- Fragments may of fallen off before ions reached detector

(The reason I havent included the meteorite answers because Krpton is the same whatever planet, adding meteorite was just a way of applying knowledge to real-life situations it didn't play any real part in the question for example "Sanjeev and Alice did an experiment" you wouldnt say Sanjeev is more reliable simple because he a boy?, the fact the krpton was apart of the meteorite was a decoy it played no part.)

. Why is it not possible to get 100% yield of N0 (1 mark)
- Not high enough Temperature/Pressure for Lead Nitrate to completely decompose
OR
- N0 make escape into air, due to being a gas

5) Which element in group 2, has the largest atomic radius?
- Lithium (1 mark)
*I assure you, they did not ask why or why there was a trend, ignore any unofficial mark scheme which say so.

I put acidic, would that get a mark or not? It is not an 'official' label but it is applying knowledge that is in the syllabus, so I am hopeful.



IIRC, the bonding questions never have any marking points on 'requiring more energy to break the bonds'. The 'final point' is usually just 'the bonds are strong/weak' so I don't think the emboldened points will be on the actual MS.



I thought Silicon was macromolecular? How can it be Si2? BTW the emboldened equation doesn't balance.



What about graphite or fullerenes (I know they aren't on the syllabus but still...)?



What about petroleum?



Zeolite is not used in catalytic converters! (That's catalytic cracking.) I think the question you refer to was 'name a catalyst used in a catalytic converter' and that was 'platinum/palladium/rhodium'. (Now that I think about it, maybe that question wasn't on either... ) There was definitely a question where the answer was 'more surface area' though...



One marking point will definitely be 'high energy/fast moving' electrons. Also, I don't think they would credit mentioning 'electron gun' for this question.



No it isnt! That is a valid response. All elements have different abundancies depending on where they come from (that is why meteorites are analysed!) I don't get your point with the 'Sanjeev' analogy as they are completely different things.



Impure lead nitrate?


Yes, but they did ask to name and explain the trend in ionisation energy - it was the question right after the Lithium one. Also, I think it was for period 2, not group 2 (if it was group 2 then we both got it wrong as i) Li is not in group 2 and ii) it has the lowest atomic radius for its group).
I disagree with a few other things in here, but I need to get some M1 revision done! Thanks for taking the time to write/edit this.

Of course you will disagree, but I'm not here to please everyone, its not possible.
I used the answers that a majority had said on the actual exam thread and cut it down to those which were most logicial. At the end of the day all we can do it sit and wait for the real results/ms, this like I said in the original post is JUST a prediction.

Of course you will disagree, but I'm not here to please everyone, its not possible.
I used the answers that a majority had said on the actual exam thread and cut it down to those which were most logicial. At the end of the day all we can do it sit and wait for the real results/ms, this like I said in the original post is JUST a prediction.

This is a prediction I have adapted and changed, so don't panic if your questions vary and questions are not in right order but I ensure you the marks are all there, if not this is all from memory remember, play nice and enjoy
[*] - Indicated my side comments

1) State this bond & How it is formed;
Covalent bond (1 mark) Shared pair of electrons *between non-metal atoms (1 mark)

2) Shapes of Molecules questions;
- BF3 (should resemble a trigonal planar shape OR t-shaped (since a previous mark scheme allows both), incorporated with two lone pairs) (1 mark)
- Angle *There is debate with this so these are what most people have said
- 120 (115-120) OR 90 (85-90) (1 mark)

- BrF4 (Should resemble Square Planar Shape, incorporated with two lone pairs) (1 mark)
- Angle: 90 (1 mark)

3) Why does KbrF4 have a higher melting point?, explain in terms of bonding.
*Therefore including structure wouldn’t gain/loose any marks if added
- Ionic bonding (1 mark) electrostatic forces/attraction between K+ and Br- oppositely charged ions (1 marks) require a lot of energy to overcome (1 mark)

4) Volume question, to be converted from cm3 to m3 s
PV = nRT or V = nRT/P (1 mark)
Correctly changing 101kpa to 101,000 pa & cm3 to m3 by x by (10 to the power of -6) (1 mark)
Answer is 0.0260 (1 marks)
*If you got 0.0175, or something like that it is because you forgot to convert cm3 tom3 or didnt convert it properly but all is not lost, since you get marks for working out


. Calculation questions for Volume of Nitric acid = 0.0524 dm3

*my working out:
8.14 / 207.2 = 0.0393
Then to get moles of n02 you times by 8/3 (due to 3:8 ratio)
so 0.0393 x 8/3 = 0.1048 moles of n02 ( 2 marks - for correct working out)

then 0.1048/ 2.00 (conc) to get volumes = 0.0524 dm3 (1 mark for correct answer and unit)

5) Which element in group 2, has the largest atomic radius?
- Lithium (1 mark)
*I assure you, they did not ask why or why there was a trend, ignore any unofficial mark scheme which say so.

6) How would HCL be labelled?
Irritant/Corrosive/Toxic (1 mark)

7) Electron Configuration; 1s2 2s2 2p6
. (N) 3- (1 mark)
. (F) - (1 mark)

*I also included the proton number/atomic number, if you also did so I highly doubt they will penalise marks for addition information, as long as it does not contradict.

. Why does Fluorine have a low melting Point?
Simple Molecular ( 1 mark)
Weak van de Waals forces between molecules ( 1 mark)


8).Name/State Formulae for Lithium Nitride
Li3N (1 mark)

. Calcium Nitride Empirical Formulae
Correctly stating percentage of Nitrogen (1 mark)
Correct method used ( 1 mark)
Ca3n2 (1 mark)

9) Balance Equation for Lead Nitrate
2___ + 2___ -----> 4___ + 1___
* You did not need to include 1 in front of the 02 at the end as this goes without saying.

10) Sulphur Compounds impact on Environment?
- (Contributed to) Acid Rain (1 mark)

11) Equation to show how CO & NO is removed in a Catalytic Converter
2NO + 2CO -> N2 + 2CO2 ( 1 mark)

12) Equation to show how Si3N4 is formed (1 mark)

3Si + 2N2 -> 3SiN4
OR
1/5 Si2+ N4 --> Si3N4
*There is debate in this however multiples are definitely allowed.


13) Atom Economy Question
Correct method (2 marks)
Correct Answer 76.4% (1 mark)
* Cant remember to what decimal place but it 76.??

14) Why does Carbon have a high melting point?
Macromolecular (1 mark)
Each carbon is covalently bonded to four other carbons (making a tetrahedral shake), networking throughout structure (1 mark)
Strong Covalent bonds ( 1 mark)
Alot of energy is required to overcome/break bonds (1 mark)

15) Completing Graph for Nitrogen
Nitrogen should be plotted with an X, lower than all other elements but NOT on 0.
( 1 mark)

16) What raw material is Hexane Obtained from?
Crude Oil ( 1 mark)

17)
. What substance/material would be used to remove Sulphur
CaO (Calcium Oxide) or CaCO3 (Limstone) ( 1 mark)
. Why is this used?
If you used CaO - It neutralised acid in Sulphur impurity (there is debate for this, I didnt personally use Ca0 so cannot give judgement) (1 mark)
. If used CaCO3 - Limestone can be easily accessed/high in abundance/ there is high supply (1 mark)

18) Draw how H-F molecules interact..
Partial Charges correctly indicated (1 mark)
3 Lone pairs of Fluoride ( 1 mark)
Hydrogen Bond (- - - -) Between Delta Plus H and Fluoride lone pair of a different molecules ( 1 mark)

19) Which type of Cracking produces high % of Alkenes?
- Thermal Cracking ( 1 mark)
State conditions required
- High Temperate and Pressure ( 1 mark)
*You could also gain these marks if you said the actual temperature and pressure required

20) State why Zeolite/Catalyst is used in Catalytic converters
- (Extremely) Large surface area for reaction to take place (1 mark)

21) How many isomers does Hexane have
5 (1 mark)

22) Name the Compound shown
2,2-dichloro-3-methlypentane

.Type of Isomer shown?
Chain Isomerism/Isomer ( 1 mark)

23) Empirical forum ale for compound
C3H6CL (1 mark)

24) How is Krypton Ionised
Electron Gun (1 mark)
bombards/hits Krpton Sample ( 1 mark)
Knocking off electrons forming possitive ions/1+ ions/2+ions ( 1 marks)

25) Ar of Krpton
For correct method (2 marks)
Correct answer to one decimal place 84.0 (1 mark)

. Give reasons why your Ar is different to that of the periodic table (1 mark)
*Again there is debate; so these are the 2 most logical answers people gave
- Mass Spectrometer used for Ar in Periodic table was of a higher resolution than that given in the table therefore answer is more precise/accurate
OR
- Fragments may of fallen off before ions reached detector

(The reason I havent included the meteorite answers because Krpton is the same whatever planet, adding meteorite was just a way of applying knowledge to real-life situations it didn't play any real part in the question for example "Sanjeev and Alice did an experiment" you wouldnt say Sanjeev is more reliable simple because he a boy?, the fact the krpton was apart of the meteorite was a decoy it played no part.)

26) Equation for 1st IE of Krypton.

Kr(g) + e- -> Kr+(g) + 2e-

Or

Kr(g) -> Kr+(g) + e-

For correct state symbols (1 mark)
for Correct equation (1 mark)

27) Explain peak at 42
- (When Krpton sample ionised) a 2+ ion charge/double charged ion was created ( 1 mark)

-

27) Which element deviates from Period 2, general trend, from Li to N
Boron (1 mark)
*If you said Oxygen this would be wrong since they've given you a boundary of from Lithium to Nitrogen

.Explain why
Outer electron is 2p Orbital, Higher energy level than Be in 2s ( 1 mark)
More shielding (as more inner main energy shells) (1 mark)

28) Processed used to obtain Hexane from Crude Oil
Fractional Distillation ( 1 mark)

29) Why it is not possible to get pure N0 on its own? (1 mark)
*There is debate with this answer; I have been suggested the most and make the most logical sense

- NO reacts with water (vapour) in air to form H2N03 (Nitric Acid)
OR
- NO reacts with air to form Nitrogen Dioxide?
OR
- NO was not only gaseous product so may of reacted with 02 to form N03 which may be hard to seperate?
*predictions here people
(- The reason why 'N0 escpaing into air' wont be accepted is because, you havent explained how that makes it impure? If the question was why can N0 not be 100% obtained/collected which is the next question then that answer would would but its talking about purity.)

. Why is it not possible to get 100% yield of N0 (1 mark)
- Not high enough Temperature/Pressure for Lead Nitrate to completely decompose
OR
- N0 make escape into air, due to being a gas

There was also an equation for write equation for incomplete/complete combustion of an Octane
(cant remember)
but this was (1 mark)