AQA CHEM5 A2 Chemistry - 19th June 2013

Overall in my opinion, tougher than any past paper on this specification. Most of it should have been well answered but if you compare this paper to the other papers, the others were all the same and this one tried to put a different spin on things. I can see a lot of candidates dropping marks on the Q=mcT question, the question with Co2+ as a catalyst, and the very last question. These questions had quite a bit of weight to them as well, 2 of them were 5 markers.

Not only that, I can imagine that some people would lose marks on the E=hv questions by not understanding that a red solution actually absorbs blue light.

However, I can't see the boundaries changing that much to be honest because it's AQA :/

Lowest it has been so far is 79/100 for an A* on past papers. I can possibly imagine 76-77 being an A* on this paper? I could be wrong though :s

Reply 3001

Hippokrates

20

Original post by bananarama2

I tagged that on the end :tongue:

I think it's just variable oxidation states, because it said why can it act as not how does it act as a catalyst.

Reply 3002

Lizzie232

11

Original post by brittanna

On 8)a), would just saying that cobalt ions have variable oxidation states and so provide an alternate reaction route with a lower activation energy get you the first mark or two?

I would say one...it shows that you need to use Co2+ and Co3+ so not sure if you'll get a mark for talking about oxidations states, I may be wrong though.

Reply 3003

mulac1

2) calculate the enthalpy of solution for KBr (2)
why is the hydration enthalpy of the Cl- ion larger than that of the Br- ion? (3)
the enthalpy change for this reaction is +17.3kJmol-1 , explain why the dissolution of KBr is feasible above x degrees (2)
calculate the temperature after the KBr dissolves (5)

3) write an equation linking deltaG, deltaH and deltaS (1)
why is entropy=0 at 0K (2)
why does the line slope at the start of the graph (2)
Mark on the boiling point (1)
Why is the change L2 greater than change L1 (2)
some questions missing here...

why can this graph be represented as y=mx+c (2)
what is the significance of the deltaG value below 500K (1)
and again some questions missing here..

Reply 3004

AndyMacCormick

I didn't put it but I was asked by someone to ask this:

For the MgO bonding question, could you say it was ionic and then say you would dissolve it in water and then test the pH and it would give a basic value of around 10?

Reply 3005

_jamie

4

Original post by mulac1

2) calculate the enthalpy of solution for KBr (2)
why is the hydration enthalpy of the Cl- ion larger than that of the Br- ion? (3)
the enthalpy change for this reaction is +17.3kJmol-1 , explain why the dissolution of KBr is feasible above x degrees (2)
calculate the temperature after the KBr dissolves (5)

3) write an equation linking deltaG, deltaH and deltaS (1)
why is entropy=0 at 0K (2)
why does the line slope at the start of the graph (2)
Mark on the boiling point (1)
Why is the change L2 greater than change L1 (2)
some questions missing here...

why can this graph be represented as y=mx+c (2)
what is the significance of the deltaG value below 500K (1)
and again some questions missing here..

There was a question that involved calculating the formation enthalpy from T and Delta S

Reply 3006

mulac1

Original post by AndyMacCormick

I didn't put it but I was asked by someone to ask this:

For the MgO bonding question, could you say it was ionic and then say you would dissolve it in water and then test the pH and it would give a basic value of around 10?

unfortunately I do not think so, since Mg(OH)2 is only sparingly soluble in water.

Reply 3007

Yetix

11

For the Q=MxCxdeltaT I got 284K

What was the answer as people have been suggesting 311K but no one has confirmed it.

thanks

Reply 3008

AndyMacCormick

Questions 4b was why is SiO2 insoluble in water!

Reply 3009

ImaNeek

Original post by popnit

Thats exactly what i put

Posted from TSR Mobile

Oxidation state
Shape of complex
Number of ligands I think
But that's not what I wrote :hmmm:

Posted from TSR Mobile

Reply 3010

toddyvedda

Wait you needed to write about cobalts various oxidation states? I just said about alternate route w. lower activation energy, then wrote the two equations? God ****ing hell

Reply 3011

mulac1

Original post by _jamie

There was a question that involved calculating the formation enthalpy from T and Delta S

ok

thanks - can you remember if it was q2 or 3 ..and can you remember which compound?

Reply 3012

bananarama2

Original post by Hippokrates

I think it's just variable oxidation states, because it said why can it act as not how does it act as a catalyst.

I originally just put that. I just thought it wouldn't hurt to write down the normal cat. stuff.

Reply 3013

khalidpatel

8

Original post by mulac1

2) calculate the enthalpy of solution for KBr (2)
why is the hydration enthalpy of the Cl- ion larger than that of the Br- ion? (3)
the enthalpy change for this reaction is +17.3kJmol-1 , explain why the dissolution of KBr is feasible above x degrees (2)
calculate the temperature after the KBr dissolves (5)

3) write an equation linking deltaG, deltaH and deltaS (1)
why is entropy=0 at 0K (2)
why does the line slope at the start of the graph (2)
Mark on the boiling point (1)
Why is the change L2 greater than change L1 (2)
some questions missing here...

why can this graph be represented as y=mx+c (2)
what is the significance of the deltaG value below 500K (1)
and again some questions missing here..

Lets get some answers on these questions

Posted from TSR Mobile

Reply 3014

mulac1

Original post by AndyMacCormick

Questions 4b was why is SiO2 insoluble in water!

yep - was it 2 or 3 marks?

Reply 3015

Hippokrates

20

Original post by bananarama2

I originally just put that. I just thought it wouldn't hurt to write down the normal cat. stuff.

Sorry

Where is this markscheme, I've only seen bits of it floating around?

Reply 3016

Lizzie232

11

Original post by mulac1

yep - was it 2 or 3 marks?

Pretty sure it was 3 caus I hoped I would get 2!

Reply 3017

AndyMacCormick

Original post by mulac1

yep - was it 2 or 3 marks?

3 marks

Reply 3018

mulac1

I see thanks.. right I will try and write a MS for questions 1,4,5,6,7 and 8 then post them for 'peer-review' so to speak.
please try and remember the remaining questions for Q2 and Q3