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AQA AS-LEVEL chemistry unit 2, 23/05/2012, raw mark POLL AND MARKSCHEME

Poll

What raw mark do you think you obtained ?

How did everyone find it, please vote on the poll :biggrin:

EDIT:

Many thanks to Knocker For this markscheme:

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
(edited 11 years ago)

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Here's me PRAYING for low grade boundaries!

June 2009 was 67/100 for an A :O
Reply 2
Avatar for jqian
jqian
1
Original post by TanishaBellum
Here's me PRAYING for low grade boundaries!

June 2009 was 67/100 for an A :O


June 2009 was the first paper, so people had very little idea of what was on the mark scheme, hence a lower grade boundary.
Original post by jqian
June 2009 was the first paper, so people had very little idea of what was on the mark scheme, hence a lower grade boundary.


LOL yeah i guess :/
Reply 4
Avatar for Scott.M
Scott.M
12
I guess TSR will have on average done better than non-TSRers, so I'd probably -10 UMS from the average result on here. :P
(edited 11 years ago)
I'm hoping for a very low boundary :frown: ... I just blanked in my exam........ :frown: x
The paper did seem harder than before.

First few questions were unseen in previous exams, what did everyone put?
Reply 7
Avatar for cuckoo99
cuckoo99
13
hoping for 75/100 for an A
Reply 8
Avatar for Reversal
Reversal
I thought it was out of 80?
Original post by PineappleChristmas
The paper did seem harder than before.

First few questions were unseen in previous exams, what did everyone put?


First curve was higher up, second curve was lower down, thrid curve was the same level but reached maximum faster
Original post by Reversal
I thought it was out of 80?


its out of 100...
YES! That is what I did!

What about equilibrium questions?

First one increase, Second one....? Decrease?
Original post by PineappleChristmas
YES! That is what I did!

What about equilibrium questions?

First one increase, Second one....? Decrease?


They were both increase I swear ? ...
Reaction was endothermic in forward direction, therfore increase in temp shifts to the right, so increase in yield ?
Reply 13
Avatar for Reversal
Reversal
Original post by iAre Teh Lejend
its out of 100...


I did edexcel, that's why.
Reply 14
Avatar for Theteacake
Theteacake
What did u guys get for the q=mc(delta)T question?
Original post by Theteacake
What did u guys get for the q=mc(delta)T question?


-399kJmol^-1 :smile:
Original post by Reversal
I did edexcel, that's why.


Ahh i see, hope that went well for you :smile:
Original post by iAre Teh Lejend
First curve was higher up, second curve was lower down, thrid curve was the same level but reached maximum faster


Did they have to reach the original curve at the end???

Original post by Theteacake
What did u guys get for the q=mc(delta)T question?


ermmm -49??? And -399 for the other one??
Reply 18
Avatar for Tayberry
Tayberry
Previous grade boundaries I'm hoping the grade boundaries aren't as high as January '12 .

JAN12 A=77 B=69 C=61 D=53 E=46
JUNE11 A=79 B=69 C=59 D=49 E=39
JAN11 A=71 B=63 C=55 D=47 E=39
JUNE10 A=69 B=61 C=53 D=45 E=37
JAN10 A=71 B=63 C=55 D=47 E=39
JUNE09 A=67 B=58 C=49 D=40 E=31
Original post by CheekiiMonkii
Did they have to reach the original curve at the end???



ermmm -49??? And -399 for the other one??


Yeahh, -49 and -399, and yes they did.

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