AQA CHEM5 A2 Chemistry - 19th June 2013

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For the last question I don't no what I did some random stuff. But I ended up with a 1:3 ratio answer but then I wrote its a 1:3 ratio of chloride to cobalt though??

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Reply 3181

BobLoblawLawBlog

Original post by mulac1

sorry - I wrote this MS - it was with NaOH :smile:

That's a relief :lol:

. Thank you for producing this mark scheme (and everybody else that has contributed).

Reply 3182

AspiringGenius

Original post by erniiee

How did you find it?

I found ti quite hard. I know I messed up the qmcDT equation and some of the cobalt chemistry equalling about 10 marks. Although if grade boundaries are low and I did well enough in Chem4 and the EMPA, An A* is achievable (I hope). :s-smilie:

you?

Reply 3183

shiver1

can someone post the asnwers for Q =2, 3, and 9 please please!

Reply 3184

mulac1

Sorry- it's getting late and unfortunately the person who posted the paper (much appreciated btw) is no longer online

Reply 3185

alex7892

I dont think 1eis right I think it would be lower as there would be less ionic bonding and thus weaker covalent bonding

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Reply 3186

MedicineMann

thought that the synoptic heat question was a bit harsh, rewarding people who had to resit chem2 with such a specific question.
EDIT: got about 50 marks on that unofficial mark scheme but might have been overly harsh, hopefully low grade boundaries and the missing questions will bump me up to a high c

(edited 10 years ago)

Reply 3187

TheHeavyWeight

Original post by MedicineMann

Totally agree. They should have replaced it with a redox titration question. This is unit 5 not unit 2!

Fortunately I managed to struggle through it anyway.

Reply 3188

mulac1

The MS obviously has some questions missing :smile:

questions 2 and 3 and isn't totally accurate.. I think I invented a question :wink:

Reply 3189

Croydon'Stepper

Original post by Fergy94

For 3e) ii) was the reaction LiMnO2 + Li ---> 2Li+ + MnO2 ??

Thats not balanced...

And there was a enthalpy of solution question around.

Reply 3190

nimbusquaffle

2a) Cl- ion is a smaller ion than Br-. water is polar so contains a ~+ H+ ion. therefore Cl-is more attracted to H2O than Br- so more energy is released when hydration happens
b) 13kJmol-1
c) increase in entropy and 1mole ---> 2moles. more disordered. ΔH<tΔS. therefore ΔG<0 nd feasible.
d) have no idea!

3a)i at 0K all substances are completely ordered. moles are constant with no vibrations. absolute entropy.
ii as temperature increases entropy increases, molecules vibrate more violently becoming more disordered
iii in line with L2
iv phase change causes a sudden increase in entropy. boiling has a greater increase in entropy than melting so L2 is greater than L1.
b)i ΔG=ΔH-TΔS can be rearranged to ΔG=-ΔST + ΔH. ΔS is m (gradient) ΔH is the constant c. ΔG is y and T is x. therefore follows the same equation. ΔS is negative due to negative gradient.
ii as T increases TΔS, because ΔH is constant. as T increases ΔH - TΔS decreases, ΔG decreases.
iii not feasible
c)i -44.5 Jk-1mol-1
ii 242 kJmol-1

hopefully help, correction ma be needed! :biggrin:

(edited 10 years ago)

Reply 3191

Adam020

Grade boundary predictions people?

Reply 3192

esl_94

Original post by mulac1

Sorry- it's getting late and unfortunately the person who posted the paper (much appreciated btw) is no longer online

Sorry for the delay - I think these are Questions 6 and 7 :smile:

Again if I have missed any pages just let me know :smile:

I seem to have 18 photos on my phone and have put 17 up here but I can't work out which I have missed!

Reply 3193

connolrj01

Original post by nimbusquaffle

2a) Cl- ion is a smaller ion than Br- so has greater electronegativity. water is polar so contains a ~+ H+ ion. therefore Cl-is more attracted to H2O than Br- so more energy is released when hydration happens
b) 13kJmol-1
c) increase in entropy and 1mole ---> 2moles. more disordered. ΔH<tΔS. therefore ΔG<0 nd feasible.
d) have no idea!

3a)i at 0K all substances are completely ordered. moles are constant with no vibrations. absolute entropy.
ii as temperature increases entropy increases, molecules vibrate more violently becoming more disordered
iii in line with L2
iv phase change causes a sudden increase in entropy. boiling has a greater increase in entropy than melting so L2 is greater than L1.
b)i ΔG=ΔH-TΔS can be rearranged to ΔG=-ΔST + ΔH. ΔS is m (gradient) ΔH is the constant c. ΔG is y and T is x. therefore follows the same equation. ΔS is negative due to negative gradient.
ii as T increases TΔS, because ΔH is constant. as T increases ΔH - TΔS decreases, ΔG decreases.
iii becomes feasible
c)i -44.5 Jk-1mol-1
ii 242 kJmol-1

hopefully help, correction ma be needed! :biggrin:

3 b iii) is that the temperatures below 500K the reaction isn't feasible, as deltaG is greater than 0 at them values

Reply 3194

Croydon'Stepper

Original post by nimbusquaffle

2a, you don't talk about electro negativity as it's not a covalent bond.

2b I did the correct method, got -7kJmol-1, but I think I ****ed up the actually calculations

Other than that, got the same as you! :biggrin:

Reply 3195

BobLoblawLawBlog

On the last part of the last question (why the ratio isn't what you'd expect it to be), do you think that saying the reactants contained impurities may get a mark?

Reply 3196

naeemkhan12

can somebody update the mrkscheme
and make it correct

Reply 3197

nimbusquaffle

Original post by connolrj01

3 b iii) is that the temperatures below 500K the reaction isn't feasible, as deltaG is greater than 0 at them values

I think that below 500K ΔG is negative so reaction becomes feasible but I may be wrong :/

Reply 3198

alex7892

I neeed 97 UMS to get an A overall.. Do you think that 72 willcbe enough? The grade boundary must be one of the lowest it has ever been? Im guessing ariund 69 for an A? Any re-assurance/ replies would be amazing! 97 ums will only be one mark over the a boundary. Thank you very much guys!!

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