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Ocr f321 23 may 2013~official discussion thread

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Reply 1520
Avatar for Ché.
Ché.
Original post by Dr. Django
between 77 and 81 i'd say ( more probably high 70's)


I hope to get somewhere in the eighties...
81 = 90% so I hope to gain that!

Thank you very much...


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Original post by lucilleJR
would anyone like to take a guess at what 51/60 would be as ums? thanks


I'm guessing approximately 75 ums maybe a bit less?
Reply 1522
Avatar for Ché.
Ché.
Original post by kingmango
I'm guessing approximately 75 ums maybe a bit less?


49/60 = 72 UMS, according to January 2013.
So?

75 sounds about right!


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Altogether with both exams and coursework, is 240 ums an A?
Original post by Liberty.
Did you get a high A in your practicals?
Or does some how that all work out to getting an A, if so MORE HOPE, YAY. :biggrin:


Low A in practicals :/ but I doubt a B would be 49/60 like what people are saying
Original post by kingmango
I'm guessing approximately 75 ums maybe a bit less?

most of you are pathetic at guessing,in jan we guessed 52-51 it was 49,this exam was harder than jan,jan was pips but we failed and revised harder,this time again your saying 51-52 for A,comeback in august,it will be 48
What do people think you'l need minimum for a grade B?
Original post by yodawg321
Low A in practicals :/ but I doubt a B would be 49/60 like what people are saying


I think I've got 46/60 :frown: I hope that's a B minimum, I think I at least deserve that! Such silly mistakes.
I managed to get 35/40 for my practicals, is that an A?
Original post by Harryshah
What do people think you'l need minimum for a grade B?


44
Reply 1529
Avatar for Saif95
Saif95
12
Original post by Liberty.
Dropped like 10-12, such silly mistakes! :sad:
If only the grade boundaries were more like Physics.


WOW! Physics boundaries are quite low!!

Is it because it is harder??
Reply 1530
Avatar for Ucki
Ucki
1
Hey, everyone!
Just few questions for you's:

Does it matter (i.e. will I be penalised for) if I write Al+3 instead of Al3+ and the same with the other ion that I can't recall now? They can't seriously drop me 2 marks for that :eek:.
Did anyone see any ALLOWs or DO NOT MARKs in similar cases in any past paper?

By the way, is the F-B-F bond after bonding with ammonia 109.5? First, I thought that as well but then I put 118... because there are still 2 unpaired and unbonded electrons in boron... so the repulsion can't be exactly 109.5 as it would be if there were just 4 bonded pairs and no unbonded electrons. You know what I mean?
(edited 10 years ago)
Original post by Saif95
WOW! Physics boundaries are quite low!!

Is it because it is harder??


It is a lot harder to grasp :smile: I believe it's around 44-47 for an A.
Easy for the natural mathematicians (not me). :tongue:
Original post by Ucki
Hey, everyone!
Just few questions for you's:

Does it matter (i.e. will I be penalised for) if I write Al+3 instead of Al3+ and the same with the other ion that I recall now? They can't seriously drop me 2 marks for that :eek:.
Did anyone see any ALLOWs or DO NOT MARKs in similar cases in any past paper?

By the way, is the F-B-F bond after bonding with ammonia 109.5? First, I thought that as well but then I put 118... because there are still 2 unpaired and unbonded electrons in boron... so the repulsion can't be exactly 109.5 as it would be if there were just 4 bonded pairs and no unbonded electrons. You know what I mean?


I'm sure the charge will be fine, if not sew them :tongue: because that would be ridiculous.
I believe everyone has agreed at 109.5 due to lone pair and 3 bonded, repulsion and what not.
I forgot to read the question properly, so I thought they were asking for the angle of the whole molecule some how. :redface:
Reply 1533
Avatar for Ucki
Ucki
1
Original post by Saif95
WOW! Physics boundaries are quite low!!

Is it because it is harder??


How do you know? How long does it take for boundaries to appear on Internet? Sorry, but I had to ask :biggrin: I'm resident only for a year... so I am a bit confused sometimes. Have they already released boundaries for F211 Biology? :biggrin: Thanks
Reply 1534
Avatar for ELBOYZ
ELBOYZ
9
I got 50. hope thats an A
Why PH3 has lower b.p than NH3 is it because in PH3 there are weaker intermolecular forces (van der waals forces) so less energy needed to break bonds

Bond angles I got 107 for first one and 109.5
Original post by Ucki
How do you know? How long does it take for boundaries to appear on Internet? Sorry, but I had to ask :biggrin: I'm resident only for a year... so I am a bit confused sometimes. Have they already released boundaries for F211 Biology? :biggrin: Thanks


People look at past papers boundaries and compare the difficulty :tongue: There's a thread for F211 where people have predicted them.
Reply 1537
Avatar for Young-Ah
Young-Ah
Original post by chigyy
Unofficial mark scheme anyone?



UNOFFICIAL MARKSHEME

1a)The mass of an isotope compared with 1/12th of the mass of C-12
ii) In this order:
19, 20
40, 18
b)1s2 2s2 2p6 3s2 3p2
c) 1(8.505/170.1) x 6.02 x10^23 = 3.01 x10^22
c) ii) K+ cl-
cl- k+
2a)
Al^3+ and SO4 ^2-
ii) Al2O3 (s)+ 3H2SO4 (aq) = Al2(SO4)3(s) + 3H2O (l)
iii) The water molecules present in the hydrated salt
iv) 6.846/342.3= 0.02mol , 12.606-6.846=5.76g , 5.76/18=0.32mol , 0.32/0.02= 16
2b) cl2 + h20 = HCl + HClo
goes red as HCL is acidic so it reacts with the litmus paper

ii) ClO-

3a) P oxidised from 0 to +1, P reduced from 0 to -1, oxidised and reduced, thus disproportionation
ii) 1.86/124=0.015 , ratio 1:1, thus 0.015 x 24000 = 360cm3
ci) The acid (H3PO4) replaced the H+ ion with a positive ion (Na+)
cii) (15/1000) x 0.1 = 1.5x10^-3 mol
ciii) 1.5x10^-3 x 3 = 4.5x10^-3 / 0.2 = 0.0225 x 1000 = 22.5cm2
d) Hydrogen bonds and van der waal forces
van der waal forces
ii) NH3 has Hydrogen bonds which require more energy to break, PH3 doesn’t.

e) Shared pair of electron, where both electron come from one atom.
ii) That molecule

ii) 120
109.5
iv) Lone pairs of electrons repel more than bonded pairs of electrons, NH3 has one lone pair of electrons and three bonded pairs of electrons, H3NBF3 has all bonded pairs of electrons , and they all equally repel
4a) Reactivity increases down the group,
• with weaker nuclear attraction between nucleus and outer electron due to larger atomic radius and a further distance from the nucleus to outer electron, this allows the outer electrons to be removed more easily
• more shielding, which outweighs the increasing nuclear charge
• smaller ionisation energy
• more shells

4bi) AgNO3 (Silver Nitrate)
4bii) A yellow precipitate would be produced
4biii) Ag+ (aq) + I- (aq) ---> AgI (s)
4biv) aqueous concentrated ammonia
5a)
• Smaller atomic radius across period
• same or similar shielding from inner electrons
• increasing nuclear charge
• shorter distance from outer electrons to the nucleus

ii) they are allotropes of carbon
b) Giant, Covalent, VDW forces,
positive ions and delocalised electrons, carbon to carbon atoms , fluorine molecules.


Not sure if these are all right~
Think Im on around 47-52 yey! Would I get any marks in the NH3 and PH3 questions if I started rambling about atomic radii (silly me) rather than the intermolecular forces?
Original post by HelenPaddock
Think Im on around 47-52 yey! Would I get any marks in the NH3 and PH3 questions if I started rambling about atomic radii (silly me) rather than the intermolecular forces?


Don't think so, I'm afraid.

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