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

Yes it is, but the question asked for it in Dm3, which is where we all went wrong, including myself since our mind were telling us m3.

but dont worry you get marks, as ive already stated in my mark scheme
for PV = nRT and changing Kpa to PA

PV = nRT or V = nRT/P (1 mark)
Correctly changing 101kpa to 101,000 pa (1 mark) (however you may also need to correctl have converted the volumes to dm3, to get this mark)

Omg the part I highlighted that you said made me laugh *Cant Breathe* *Dying of Laughter* but I think they based that story on me, since my mum says a 17 year old girl shouldnt weight 8.5 stone and I should eat more.. but thats another story

Yeah hopefully your right, and Britanna just told me they asked for moles and answer was 0.0260, so ive added another 3 marks to my score which put me to 10-12 wrong and with your predicted grade boundaries definately an A There, which I need (since i fudged up psychology and edexcel biology were being evil bizatches)

Tbh, never rely on Text books alone, thats how I learn t-shaped so hopefully I get atleast 1 mark, for Bf3, I put 115 for the angle tho since I was thinking trigonal planar is 120 so minus 2 lone pairs (-4/5 degrees) and somehow got 115 lol fail

I am actually going to cry when the results come out. Yes I am male.

I think chemistry is an acceptable reason for men to cry. No homo.

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 dm3 NOT m3
PV = nRT or V = nRT/P (1 mark)
Correctly changing 101kpa to 101,000 pa (1 mark) (however you may also need to correctl have converted the volumes to dm3, to get this mark)
Answer is 0.0175 (1 marks)
*Myself and others put 0.0260, and I can hapilly admit that is wrong people, since we had to convert it to dm3 and we made it to m3 which is usually asked. However, you get marks for working out, so all is not wrong

Alternative view:
They asked for Moles, if so answer is 0.0260 and you will gain 3/3 marks.

. 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 Delta Minus F on 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)

(- 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 Alkane (cant remember)
but this was (1 mark)

I think chemistry is an acceptable reason for men to cry. No homo.

I am actually going to cry when the results come out. Yes I am male.

No they didn't ask for dm3, do you understand that YOU CAN'T USE DM3 IN THE EQUATION? I'm sorry but seeing as you have ignored the post of another person with just letting it go as a joke, I had to capitalize it. Plus how the hell would it be 0.0175? That's BS. pressure is 101000, Volume is 638 cm^3, R is 8.31 and T is 298K, now get 0.0175. Impossible.

And wtf? Obviously they asked for moles, why would you get a mark for V = nRT/p when it has got nothing to do with the equation. They asked for moles, becasue Volume was already given and it is 638 cm^3.

I'm pretty sure Buttercup doesn't have a mum... Is the Proffessor become transgender?

That number seems familiar although if this is the Pb question, I'm pretty sure they asked for volume... It's probably too long ago I'd be surprised if I got it wrong. My class wouldn't let me live it down, I was leading the revision session on equations two hours before the exam

Well my textbook didn't have XeF4 but I taught myself square planar (phew.) and ai think I salvaged a mark as my drawing is an alternative of the 'T-Shape' and would pass. I would lose a mark for the bond angle hough -_-

Good luck, I'm sure you'll do fine, I think I'm boned O_O

More shielding for the Boron question is not going to get a mark. The mark comes from saying more energy required. More shielding is technically incorrect, it would mean that aqa are contradicting their own mark schemes

Actually in some papers you can get a mark for mentioning partial shielding by 2s electrons, but the best answer would definitely have the fact that 2p1 is higher in energy hence less energy required to remove it

goodluck for march people, I'm sure we've done better than what we think

I think shielding would get you the mark, because it goes without saying that less energy is required which is why it deviates from the trend? lol.

But I dunnoe, Im kind of done with this now, what's done is done.
Gunna start learning for As Unit 2 for all my lessons.

goodluck for march people, I'm sure we've done better than what we think

What grade would be 38-42?

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.