AQA CHEM5 A2 Chemistry - 19th June 2013

For the Q=MxCxdeltaT I got 284K

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

thanks

There was a question on the lattice dissociation of AgCl being same, greater or equal to

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

I got the same answer as you. I was about to write down 311k but realised that enthalpy of solution is endothermic for silver chloride so it must gain heat from the surrounding water hence water temperature goes down from 298k.

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

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 think it asked about temp above 500k

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..

For KBr now being a suitable salt bridge did anyone write the Pottassium would react with the water in the solution?

for the delta s question, did you have to double the answer to find 1 mole of the product? i think it was -44.5 doubled?

I think we all agree this is the toughest paper to date. What do you mean that the grade boundaries won't be changing because it is AQA?

a. Highest state of order, no vibration
b. As T increases, more kinetic energy, more vibration, greater disorder, higher entropy
c. Below L2
d. From liquid to gas at L2, larger change in entropy
e. easy
f. ( 1 mark) becomes feasable

what did people put about the y=mx+c question ? i put temp was gradient and it symbolised a negative correlation , thus negative gradient which it refers to in the equation??

what did people put about the y=mx+c question ? i put temp was gradient and it symbolised a negative correlation , thus negative gradient which it refers to in the equation??

what did people put about the y=mx+c question ? i put temp was gradient and it symbolised a negative correlation , thus negative gradient which it refers to in the equation??