[shuaib786]

(Original post by knocker)
UNOFFICIAL MARK SCHEME - please point out any errors (done with paper in front of me and I'm a teacher...)

1(a) steeper line, ending twice as high (2)
(b) less steep line, ending 2/5 as high (2)
(c) steeper line, ending at same level (2)
(d) concentration of reactants decreases with time, hence frequency of collisions decreases as does the rate (2)
(e) 2 H2O2 --> 2 H2O + O2 (1)
(f) The HBr is not used up (1)

2(a)(i) -49 (3)
(ii) it is an element (1)
(b) increases, 4 moles gas --> 2 moles gas, eqilibrium shifts right to oppose the change (3)
(c) increases, reaction is endothermic, equilibrium shifts right to oppose the change (3)
(d)(i) no net carbon produced (1)
(ii) CH3OH + 3/2 O2 --> CO2 + 2 H2O (1)
(iii) 3 H2 + 3/2 O2 --> 3 H2O (1)
(e) q = 4389 kJ, DH = - -399 kJ/mol (3)


3(a) balancing equation (1)
(b) P4 = zero, H3PO4 = +5 (2)
(c) Add up Ar values to show they are different to 5dp (1)
(d)(i) speeds up rate of reaction without being used up (1)
(ii) addition of water (1)
(iii) CH3CH=CH2 + H2O --> CH3CH(OH)CH3, propan-2-ol (2)

4(a) Forms brittle TiC (1)
(b)(i) 2 FeTiO3 + 7 Cl2 + 6 C --> 2 FeCl3 + 2 TiCl4 + 6 CO (1)
(ii) TiCl4 + FeCl3 + 7 Na --> Fe + Ti + 7 NaCl (1)
(c) Cu2+ + Fe --> Cu + Fe2+, Cu2+ ions reduced as they gain electrons (2)
(d) 2 O2- --> O2 + 4e (1)

5(a)(i) Ba + 2 H2O --> Ba(OH)2 + H2 (1)

(ii) reactivity increases (1)

(b) Mg(OH)2 (1)

(c) Barium meal / X-ray tracer, insoluble (2)

6(a)(i) Cl2 --> 2 Cl.
CH2Cl2 + Cl. --> .CHCl2 + HCl
.CHCl2 + Cl2 --> CHCl3 + Cl. (3)
(ii) UV light, Free-radical substitution (2)
(b)(i) CHCl3 + Cl2 --> CCl4 + HCl (1)
(ii) CHCl3 contains C-H bonds, no C-H absorption at 2850-3300 (2)
(c) CFC's - UV light breaks C-Cl bond, makes Cl. radicals
Cl. + O3 --> ClO. + O2
ClO. + O3 --> 2 O2 + Cl. chain reaction
2 O3 --> 3 O2 (4)
(d)(i) CH2=C(F)CF3 (1)
(ii) it contains no C-Cl bonds (1)

7(a)(i) elimination mechanism (3)
(ii) E hex-3-ene (H's on opposite sides) and Z-hex-3-ene (H's on same side) (2)
(iii) Same MF and SF, different arrangement of atoms in space (2)
(b) H2SO4 electrophilic addition mechanism (4)

8(a) Safety - NaOH is corrosive, Environmental - Process 2 uses CO2 from local factory, less CO2 emissions/global warming (2)
(b)(i) Nucleophilic substitution with :OH- (3)
(ii) BCA (3)
(c) Fermentation, 35oC, Yeast, aqueous, anerobic (4)
(d) primary alcohol, acidified potassium dichromate(VI)
CH2(OH)CH2CH2CH2OH + 4[O] --> HOOCCH2CH2COOH + 2 H2O (3)

9(a)(i) Iodine/I2, Cl2 + 2 I- --> 2 Cl- + I2, redox (3)
(ii) silver(I) chloride, Ag+ + Cl- --> AgCl, ppt dissolves (3)
(b)(i) H+ + Cl- --> HCl, HCl (2)
(ii) 2 I- --> I2 + 2e-
H2SO4 + 8 H+ + 8 e- --> H2S + 4 H2O
H2SO4 = oxidising agent, yellow solid = sulfur/S/S8 (4)
(iii) NaOH reacts with H+, equilibrium shifts right to make more H+ and opppose the change
bromine is used in small quantities

Thanks, im just hoping that the grade boundaries arnt as high as last year.

[knocker]

(Original post by ryanboi)
For question 3)a)iii) I put H+ and OH- instead of H2O. Would I still get that mark?
For question 8)c) I put room temperature instead of 35 degree? Is that right?
For question 9)a)i) In the textbook, it said displacement reaction aswell as redox reaction? Would putting displacement reaction get me the mark?

You mean... 2)d)iii) doubtful as it was H2O in the gaseous state
8)c) They normally accept 30-40oC from memory which isn't room temperature so possibly not (need to check in past mark schemes to confirm) -
June 2010...
Three conditions in any order for M1 to M3
M1 yeast or zymase
M2 30oC ≥ T ≤ 42 oC
M3 anaerobic / no oxygen / no air OR neutral pH
9)a)i) not sure - as you mentioned the syllabus talks about displacement too so you might be ok.

[sidra111]

(Original post by Picture~Perfect)
Hi all
As promised, here is a link to the paper, I've scanned it and uploaded to my skydive on hotmail. It may take a while to load, but you should be able to download and print it off as you wish
June 2012 paper
I'll write my interpretation of the answers in the next post

thanks

[Millyshyn]

(Original post by ryanboi)
For question 3)a)iii) I put H+ and OH- instead of H2O. Would I still get that mark?
For question 8)c) I put room temperature instead of 35 degree? Is that right?
For question 9)a)i) In the textbook, it said displacement reaction aswell as redox reaction? Would putting displacement reaction get me the mark?

Think you might get it for the first one though I'm not sure, depends on how generous the examiner is really..
Room temperature isn't the same as 35 degrees, so nope.
Probably not. Displacement is more of a GCSE term I would've thought? Not seen it mentioned in A Level papers.

Just judging from what I've seen on mark schemes.

[Ysondrae]

Oh, for question 3aii, I wrote 'adding excess water' instead of 'addition of water' - does that count as a mark?

[sreddy17]

(Original post by Picture~Perfect)
Mark scheme
This is only my interpretation, I by no means got a 100% on this paper, I'll check with the textbook to make this as accurate as possible. Please feel free to comment and suggest changes

(IN PROGRESS)

Question 1:

a) Double the original curve
b) Half the original curve
c) Steeper gradient, curve levels off at the same place as the original
d) As the reaction proceeds the reactants are used up, the curve levels off as all of the reactants are used, therefore no more product can be formed.
e)
(i)
(ii) It is reformed. A catalyst is not use up in a reaction.

Question 2:

a)
(i) -49KJmol-1
(ii) It is and element it is already formed/ by definition
b) Increases
According to Le Chatlier's principle equilibrium will shift to oppose change. Equilibrium will shift right to the side with the fewest moles.
c) Increases
According to Le Chatlier's principle equilibrium will shift to oppose change. The forward reaction is endothermic. Equilibrium will shift right.
d)
(i) An activity in which there is no net carbon diode emission to the atmoshpere.
(ii) CH3OH + 2O2 ------> CO2 + 2H2O
e) q=mc 'change in' T
q= 4389J

Sorry got to stop for now.
I'll add more later I have some prep to finish and a tutorial.

2d) ii) is wrong

[Science211]

What do you think the grade boundaries for an A will be? Thanks

[Strangeclouds]

(Original post by knocker)
UNOFFICIAL MARK SCHEME - please point out any errors (done with paper in front of me and I'm a teacher...)

1(a) steeper line, ending twice as high (2)
(b) less steep line, ending 2/5 as high (2)
(c) steeper line, ending at same level (2)
(d) concentration of reactants decreases with time, hence frequency of collisions decreases as does the rate (2)
(e) 2 H2O2 --> 2 H2O + O2 (1)
(f) The HBr is not used up (1)

2(a)(i) -49 (3)
(ii) it is an element (1)
(b) increases, 4 moles gas --> 2 moles gas, eqilibrium shifts right to oppose the change (3)
(c) increases, reaction is endothermic, equilibrium shifts right to oppose the change (3)
(d)(i) no net carbon produced (1)
(ii) CH3OH + 3/2 O2 --> CO2 + 2 H2O (1)
(iii) 3 H2 + 3/2 O2 --> 3 H2O (1)
(e) q = 4389 kJ, DH = - -399 kJ/mol (3)


3(a) balancing equation (1)
(b) P4 = zero, H3PO4 = +5 (2)
(c) Add up Ar values to show they are different to 5dp (1)
(d)(i) speeds up rate of reaction without being used up (1)
(ii) addition of water (1)
(iii) CH3CH=CH2 + H2O --> CH3CH(OH)CH3, propan-2-ol (2)

4(a) Forms brittle TiC (1)
(b)(i) 2 FeTiO3 + 7 Cl2 + 6 C --> 2 FeCl3 + 2 TiCl4 + 6 CO (1)
(ii) TiCl4 + FeCl3 + 7 Na --> Fe + Ti + 7 NaCl (1)
(c) Cu2+ + Fe --> Cu + Fe2+, Cu2+ ions reduced as they gain electrons (2)
(d) 2 O2- --> O2 + 4e (1)

5(a)(i) Ba + 2 H2O --> Ba(OH)2 + H2 (1)

(ii) reactivity increases (1)

(b) Mg(OH)2 (1)

(c) Barium meal / X-ray tracer, insoluble (2)

6(a)(i) Cl2 --> 2 Cl.
CH2Cl2 + Cl. --> .CHCl2 + HCl
.CHCl2 + Cl2 --> CHCl3 + Cl. (3)
(ii) UV light, Free-radical substitution (2)
(b)(i) CHCl3 + Cl2 --> CCl4 + HCl (1)
(ii) CHCl3 contains C-H bonds, no C-H absorption at 2850-3300 (2)
(c) CFC's - UV light breaks C-Cl bond, makes Cl. radicals
Cl. + O3 --> ClO. + O2
ClO. + O3 --> 2 O2 + Cl. chain reaction
2 O3 --> 3 O2 (4)
(d)(i) CH2=C(F)CF3 (1)
(ii) it contains no C-Cl bonds (1)

7(a)(i) elimination mechanism (3)
(ii) E hex-3-ene (H's on opposite sides) and Z-hex-3-ene (H's on same side) (2)
(iii) Same MF and SF, different arrangement of atoms in space (2)
(b) H2SO4 electrophilic addition mechanism (4)

8(a) Safety - NaOH is corrosive, Environmental - Process 2 uses CO2 from local factory, less CO2 emissions/global warming (2)
(b)(i) Nucleophilic substitution with :OH- (3)
(ii) BCA (3)
(c) Fermentation, 35oC, Yeast, aqueous, anerobic (4)
(d) primary alcohol, acidified potassium dichromate(VI)
CH2(OH)CH2CH2CH2OH + 4[O] --> HOOCCH2CH2COOH + 2 H2O (3)

9(a)(i) Iodine/I2, Cl2 + 2 I- --> 2 Cl- + I2, redox (3)
(ii) silver(I) chloride, Ag+ + Cl- --> AgCl, ppt dissolves (3)
(b)(i) H+ + Cl- --> HCl, HCl (2)
(ii) 2 I- --> I2 + 2e-
H2SO4 + 8 H+ + 8 e- --> H2S + 4 H2O
H2SO4 = oxidising agent, yellow solid = sulfur/S/S8 (4)
(iii) NaOH reacts with H+, equilibrium shifts right to make more H+ and opppose the change
bromine is used in small quantities

I'm fairly sure it was ACB for 8bii.

Also, surely 'NaOH is corrosive', for 8a is a bit of a weak answer, NaOH is used for lots of things? I put Bromine is toxic, not sure what the correct answer is, but hey I'd be surprised if it was as simple as NaOH is corrosive.

[knocker]

(Original post by Ysondrae)
Oh, for question 3aii, I wrote 'adding excess water' instead of 'addition of water' - does that count as a mark?

If you got 'adding' and 'water' you should be fine.

[-Liberty]

What is the UMS likely to be? Thanks so much for this OP.

[Ysondrae]

(Original post by knocker)
If you got 'adding' and 'water' you should be fine.

Thanks, I got told by my friends that hydration was the breaking of a double bond Also for question 4a, instead of 'Forms brittle TiC' I wrote 'forms an impure product/titanium carbide,' would that count too?

[knocker]

(Original post by Strangeclouds)
I'm fairly sure it was ACB for 8bii.

Also, surely 'NaOH is corrosive', for 8a is a bit of a weak answer, NaOH is used for lots of things? I put Bromine is toxic, not sure what the correct answer is, but hey I'd be surprised if it was as simple as NaOH is corrosive.

110% certain it is BCA

Just because something is used for lots of things doesn't mean it can't be dangerous.

They accept correct safety hazards in the ISA's so why not here. The only other thing I could think of is that Process 2 can be done at a low temperatures (30-40oC) whereas they probably do Process 1 at high temperatures.

[Tullia]

(Original post by Strangeclouds)
I'm fairly sure it was ACB for 8bii.

It wasn't.

[Tullia]

(Original post by knocker)
110% certain it is BCA

It was.

[maramore]

For 'hydration' do you think 'the addition of water across a double bond' is okay?

And for the question where you had to add 4[O] do you think if I wrote C4H10O2 instead of CH2(OH)CH2CH2CH2OH and C4H6O4 instead of HOOCCH2CH2COOH that I'd get the marks?

Aaand... for the safety question, do you think just writing "The process is explosive" would get you the mark

Damnit. I thought it was an okay paper but then when I walked out someone told me about the elimation mechanism arrows you had to draw and I was just like WHAT, I didn't even see the question. Annoyed.

Thanks so much for the paper/markscheme by the way

[Strangeclouds]

(Original post by knocker)
110% certain it is BCA

Just because something is used for lots of things doesn't mean it can't be dangerous.

They accept correct safety hazards in the ISA's so why not here. The only other thing I could think of is that Process 2 can be done at a low temperatures (30-40oC) whereas they probably do Process 1 at high temperatures.

Go on, show me how it was BCA? I got ACB and this Chemistry don in my year got ACB as well, so I was happy, buuuttt...

(Original post by Tullia)
It wasn't.

Show me how?

[maramore]

First one had the alcohol peak, third one had the acid peak. Definitely.

[ijaz]

what about normal MPa for the yeast fermentation question

[erniiee]

(Original post by knocker)
110% certain it is BCA

Just because something is used for lots of things doesn't mean it can't be dangerous.

They accept correct safety hazards in the ISA's so why not here. The only other thing I could think of is that Process 2 can be done at a low temperatures (30-40oC) whereas they probably do Process 1 at high temperatures.

Do you think they'd accept high pressures? :s

Also, using your professional judgement () how do you think this paper compares to others? Do you think the grade boundaries will be higher or lower than normal? If I go by your markscheme I think I've got between 75-80 so I think I may scrape an A with the recent higher grade boundaries :/

[Tullia]

(Original post by Strangeclouds)
Show me how?

Just look and you'll see. For starters, just take compound A and it matches with the 3rd IR spectra.

It was B,C and A.