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

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Reply 40

Miyata

Original post by David_Skiller

easiest paper ever......defo 140 :colone:

is aqa unit2 paper out of 140 ums? lol I thought even if its out of 100 marks, ums would be 100 as well.

Reply 41

alan-93

this was the second time i did this paper, i did it last time in june 2011 and i got a c! I thought it was all alright apart from that it was lots of HSW questions! I'm guessing that i have lost at most 11 marks! so i'm expecting at least 89/100. And yh i gotta say it was hard if you were an AS student and it was your first time doing this!

(edited 11 years ago)

Reply 42

alan-93

Original post by Miyata

is aqa unit2 paper out of 140 ums? lol I thought even if its out of 100 marks, ums would be 100 as well.

its out of 140/ums so every mark is worth of 1.2 ums marks! It's the biggest unit of all a-level chemistry tho!

Reply 43

Miyata

Original post by alan-93

its out of 140/ums so every mark is worth of 1.2 ums marks! It's the biggest unit of all a-level chemistry tho!

oh, cool. Thanks for letting me know.

Reply 44

blueclearsky

found the exam tough! nothing like the past papers... i hope the grade boundries are low. what do you think you'll need to get an A in this unit? found unit 1 annoying aswell.. dont know whats up with chemistry this year. apparantly there's a new examiner this year hence the difference in structure for the Jan and now this paper. hmmm

Reply 45

David_Skiller

Original post by Miyata

is aqa unit2 paper out of 140 ums? lol I thought even if its out of 100 marks, ums would be 100 as well.

raw marks/100 ums/100

i thought this paper was just cropped sections from other past papers?

iaretehlejend is crying for no reason :biggrin:

Reply 46

takius123

Oh flippin' heck! I forgot to stick minus on 399!! Looks like 1/3 :frown:

Reply 47

student164

What do you all reckon it'll be for full ums?

jan 2012 - 93
june 20122 - 99

I thought this was harder than both, but is that just wishful thinking haha

Reply 48

takius123

What did everyone put on the question about the safety reason for the question about converting something where they use microorganisms that use CO2?

Reply 49

Catalyst

Original post by takius123

What did everyone put on the question about the safety reason for the question about converting something where they use microorganisms that use CO2?

The one with but 1,4 diol?
I believe it was something to do with it being extremly flammable.

Reply 50

takius123

Original post by Catalyst

The one with but 1,4 diol?
I believe it was something to do with it being extremly flammable.

I thought the paper just said only the CO2 is transported :eek:

Oh noes haha!

Reply 51

Chicken Bacon

Original post by jonathanf-s

oi what about the ionic equations is any gunna put on an unofficial mark scheme on ??

check first post

Reply 52

Chicken Bacon

Original post by takius123

I thought the paper just said only the CO2 is transported :eek:

Oh noes haha!

check first post for ms :smile:

Reply 53

Chlomc

Im getting really worried now. Im supposed to be doing chemistry unit 2 but it says tomorrow on my exam timetable.. but now im thinking that was a mistake :s

Reply 54

Chicken Bacon

Original post by Chlomc

Im getting really worried now. Im supposed to be doing chemistry unit 2 but it says tomorrow on my exam timetable.. but now im thinking that was a mistake :s

This is AQA, maybe your doing edexcel or OCR ?

Reply 55

Chlomc

Original post by iAre Teh Lejend

This is AQA, maybe your doing edexcel or OCR ?

Nope it's definitely AQA

Reply 56

Chicken Bacon

Original post by Chlomc

Nope it's definitely AQA

Woah.... your school owned you...

Reply 57

takius123

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) <-- What's the question in this one? I somehow can't remember this :biggrin:

(f) The HBr is not used up (1) <-- Ah! I remember this one :biggrin:

. I remember doing a similar question and the answer has to be 'Br provides an alternative route with lower activation energy' .. Let's hope it's possible to get the mark by saying it is not used up :smile:

2(a)(i) -49 (3)
(ii) it is an element (1) <-- I think you have to say that the element is in its standard state. Because some elements can still have a value if they're not in standard states
(b) increases, 4 moles gas --> 2 moles gas, eqilibrium shifts right to oppose the change (3) <-- Most MS I've seen says that one cannot just simply state 'to oppose the change'. Apparently, one must state 'to oppose the increase in pressure/temp etc.' .. talk about being pedantic!
(c) increases, reaction is endothermic, equilibrium shifts right to oppose the change (3)
(d)(i) no net carbon produced (1) Most MS underline the 'to air/atmosphere'
(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) Darn, 1 mark for 399, instead of -399 :frown:

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) This can be multiples :biggrin:

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) <-- you can also put that only flourine is the halogen bonded to this compound :biggrin:

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) <-- Wasn't this question about CO2 obtained from other factory, needed by the microorganisms? How come the safety is about NaOH being corrosive :eek:

My answer to this question seems rather odd - CO2 needed to be transported, so usually stored in a high pressure container. So there's risk of boom! haha :biggrin:

(b)(i) Nucleophilic substitution with :OH- (3)
(ii) BCA (3)
(c) Fermentation, 35oC, Yeast, aqueous, anerobic (4) <-- Temp can be from 30-42C apparently
(d) primary alcohol, acidified potassium dichromate(VI) Acid used can be H2SO4
CH2(OH)CH2CH2CH2OH + 4[O] --> HOOCCH2CH2COOH + 2 H2O (3) Ack! Why did I not think of producing water, instead of hydrogen gas :tongue:

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 think you can say that the health benefit outweighs the risk as well :biggrin:

(edited 11 years ago)

Reply 58

Catalyst

Looks like I got about 80/100 raw :/
Does anyone thing this will be 124/140 ums?

Reply 59

Chlomc

Original post by iAre Teh Lejend

Woah.... your school owned you...

I know im really confused :s I checked with a few friends and they all have the same date for chemistry unit 2 which is tomorrow. This is GCSE not a level right?