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AS Chemistry 2016 Unofficial Mark scheme

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What did everyone write for the observation of NaClO and some other chemical, was it black solid/brown solution of I2 as it was displacement?
Original post by IntellectualBoss
What did everyone write for the observation of NaClO and some other chemical, was it black solid/brown solution of I2 as it was displacement?


i think it was potassium or sumething with iodide and then chlorine came into it but yes was displacement
Reply 122
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Ainika
Original post by DaVinciGirl
Was SiO2 a macromolecular?

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Silicon, Graphite and Diamond are the only macromolecular structures, hope that helps in future! (Only ones we need to know anyway)
Reply 123
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Ainika
Original post by SANTR
What I meant was the raw mark has to be 80% of the total (80). Therefore the lowest mark for an A is 64/80.


The grade boundaries are based on our results. 100% is not the full 80 marks on the paper but the highest mark anyone got. So unless someone got al the marks on the paper, 100% won't be 80 marks. Then the rest is calculated from there but the % grade boundaries only differ by 2-3.
Original post by IntellectualBoss
Thats correct but when transition metals lose electrons they lose from their s shell first so its 3d3


I saw a similar question on a pat paper and it was the 4s electron that was lost first because it a higher energy level 👍
I put the solution turns brown
Original post by IntellectualBoss
Alright I've put together a couple questions I remember from the exam and the answers, put through your questions or answers you dont agree with!

1.) chromium ion, 1s2 2s2 2p6 3s2 3p6 3d3
2.)aluminium 1s2 2s2 2p6 3s2 3p1
which ion has the same structure as krypton with a 2+ charge- strontium
which compound has a ion with 2+ from argon and 3- from argon- Ca3P2
bromine mass spectrum- 50% at 158 and 50% at 162
5 marks on bromine and magnesium
6 marks on practical
find average titre value and use this to find moles of MHCO3 reacted- 0.102 conc of hcl 250cm3 in 25cm3 amounts. something .7 and the moles are 0.041
rmm is 149


Original post by IntellectualBoss
Alright I've put together a couple questions I remember from the exam and the answers, put through your questions or answers you dont agree with!

1.) chromium ion, 1s2 2s2 2p6 3s2 3p6 3d3
2.)aluminium 1s2 2s2 2p6 3s2 3p1
which ion has the same structure as krypton with a 2+ charge- strontium
which compound has a ion with 2+ from argon and 3- from argon- Ca3P2
bromine mass spectrum- 50% at 158 and 50% at 162
5 marks on bromine and magnesium
6 marks on practical
find average titre value and use this to find moles of MHCO3 reacted- 0.102 conc of hcl 250cm3 in 25cm3 amounts. something .7 and the moles are 0.041
rmm is 149


For the bromine mass spectrum it should have been 25% at 158, 50% at 160 and 25% at 162
Original post by Testman280
For the bromine mass spectrum it should have been 25% at 158, 50% at 160 and 25% at 162


Yes! I got that
Original post by nadeu01
what did everyone think of the exam doe?:frown:


redicously Hard????
How many marks was the bromine mass spectrum one? 2??
Original post by Hbassett26
How many marks was the bromine mass spectrum one? 2??


Yeah 2


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Reply 131
Avatar for Dowel
Dowel
8
Original post by IntellectualBoss
Thats correct but when transition metals lose electrons they lose from their s shell first so its 3d3


Chromium is an exception to that, it loses 1 electron from 4s before the 3d
Reply 132
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SM-
6
Was there any question on this paper with an answer of 138?
Original post by IntellectualBoss
It was incredibly difficult and I got 93% in the specimen paper which everyone said was hard, I would expect grade boundaries to be around 70% for A.


do you really think because spec papers were so much easier and i dont think i got an a or b im really scared and dont know what to do
Original post by DaVinciGirl
I think this was a question
Mg2+ and Na+ which is has the smallest atomic radii?
I wrote Mg as it has same shielding, and number of electrons but has more protons. So more nuclear attraction between electron and nucleus.

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i said that is it correct because they have same radius and shielding but mg has higher charge
Original post by uud
Question about velocity of 52Cr+. Is V=1.714X10^6 ms^-1


i got that but wrote it as full no.
Original post by SANTR
That's very true but all the papers in the last decade have not been of the same difficulty.
Some have been harder than others yet the grade boundaries have remained the same, at 80%?


yh its 80% but raw marks are different they make 60 as 80% interms of ums etc
Original post by SM-
Was there any question on this paper with an answer of 138?


Maybe the mass spec question?
Original post by DaVinciGirl
Maybe the mass spec question?


Yh it was 180 but basically I got the right working out and wrote it down but wrote it wrong on my calculator do you think I will get half the marks because I worked out it was 20%
Original post by DaVinciGirl
Maybe the mass spec question?


Also question basically I made quite a bit of errors on the Marsha question and I don't think I got an A so is it possible to still get a B after doing the secong paper I think I got like a c or low b but c mainly.


And any predictions for the secong paper it will be help ful thanks

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