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# Ocr f321 23 may 2013~official discussion thread watch

1. (Original post by Onkar-M)
I remember doing the 8o2 in the exam though.
Something about that is wrong I can't even remember
You can balance it with whole numbers, I find it easier with fraction in those cases Sometimes it mind-boggles me otherwise.
2. I am now convinced that I am sitting on unofficial 54/60!?
Careless mistakes hinders my performance, but its still there!

I hope everyone found the paper highly accessible in most cases of course!

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3. (Original post by Dr. Django)
At lowest a very high B, at best around 90%
really want an A what do you think it will be??
4. How much UMS would 54/60 give myself?

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5. so annoyed with myself, i put tsilver nitrate and yellow precipitate then crossed it out later
6. (Original post by amar9kan)
really want an A what do you think it will be??
I think 50, but others are saying 47/48
7. Unofficial mark scheme anyone?
8. (Original post by Ché.)
How much UMS would 54/60 give myself?

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between 77 and 81 i'd say ( more probably high 70's)
9. (Original post by jphoenix18)
so annoyed with myself, i put tsilver nitrate and yellow precipitate then crossed it out later
same here! The more I read the question, the more I confused myself :L Luckily they were only 1 markers...
10. (Original post by hwilliams06)
same here! The more I read the question, the more I confused myself :L Luckily they were only 1 markers...
I put conc ammonia then i crossed it out and put nitric acid -.-
11. (Original post by Dr. Django)
At lowest a very high B, at best around 90%
You're saying 49/60 will be a B. So according to you 81% is a B?
12. (Original post by theCreator)
UNOFFICIAL MARKSCHEME F321

1a)i) The mass of an atom of an isotope of an element compared with 1/12 of the mass of an atom of c-12.

a)ii) 39K ~19 protons 20 neutrons 19 electrons
41K+ ~19 protons 22neutrons 18electrons
b) 1s2, 2s2, 2p6, 3s2, 3p2
c)i) 3.01 x10 ^22

c)ii) Alternating K+ and Cl- Ions (But simply + and – is also acceptable.
2)a)i) 2 Main ions are Al(3+) and (SO4)2-
ii) Al203 (s) + 3H2SO4 (aq) ---> Al2(SO4)3 (aq) + 3H2O (l)
iii) x represents the number of water molecules present in the crystalline structure (water of crystallisation)
iv) x=16
b)i) It turns red because HCl is an Acid
ii) ClO-

3)a)i) P has been both reduced and oxidised. Oxidised from 0 to +3 and reduced from 0 to -1.
ii) volume of PH3 = 360cm^3
b) 4PH3 + 802 ---> P4H10 + 6H20
c)i) Because the H+ ions have been replaced with a metal ion, in this case Zn.
ii) Moles of H3PO4 = 0.0015
iii) 22.5cm^3
d)i) NH3 = Hydrogen Bonding, PH3 = Permant Dipole-Dipole attraction
ii) Because hydrogen bonding is a stronger intermolecular force requiring more energy to break
e)i) A shared pair of electrons supplied by one of the bonding atoms only.
ii) Essentially the same as in the diagram on the earlier page on the dative covalent bond is labelled between nitrogen and boron.
iii) BF3 = 120*, H3NBF3 = 109.5*
iv) To put it shortly NH3 has 3 bond pairs and 1 lone pair giving it an angle of 107*, but now in H3NBF3 it has 4 bond pairs and no lone pairs making it assume the tetrahedral shape with an angle of 109.5*.

4a) -increase nuclear charge outweighed by increase atomic radius
-more shells;more electrons;more inner shielding effect by inner electrons;
decrease nuclear attraction. easier to remove outer elect to react with halogens. reactivity increases hence reaction more vigorous down the group
b)i) AgNO3 (Silver Nitrate)
ii) A yellow precipitate would be produced
iii) Ag+ (aq) + I- (aq) ---> AgI (s)
iv) concentrated NH3 (ammonia)

5)a)i) Across the period, atomic radius decreases and nuclear charge increases making the attraction between the nucleus and outermost electron stronger and require more energy to break. (The electron shielding effect also remains the same).
ii) It is unnecessary because first ionisation energy takes place when the atoms are gaseous, so there would be no giant covalent structure anyway.

5b) Fill the boxes in of the table stating the properties of lithium, carbon and fluorine (6)

Li = Bottom box: Delocalised electrons
C = Top box: Giant Covalent, Middle Box: Covalent bonds, Bottom Box: Again covalent bond or a shared pair of electrons
F2 = Middle box: van der Waal’s forces, Bottom Box: None since there are no particles between the molecules.
Could you please tell me if the paper has been posted? If so what page is it on?
13. (Original post by yodawg321)
You're saying 49/60 will be a B. So according to you 81% is a B?
To be fair is had been 50+ for an A previously, and as the papers content wasn't difficult, just tricky it's likely to be similar.
14. (Original post by yodawg321)
You're saying 49/60 will be a B. So according to you 81% is a B?
In the past 52 has been the A boundary. Raw marks are converted to UMS marks (/90) depending on how the cohort found the exam.

This basically maintains the proportion of people that get an A each year and stops people being disadvantaged if their exam was particuarly difficult.

Therefore, 49/60 which is indeed over 80% in raw marks MAY not be an A after UMS scaling if in general people found the paper slightly easier than average
15. (Original post by Saif95)
Could you please tell me if the paper has been posted? If so what page is it on?
page 68 and then the missing page 11 from the test paper is found a few pages after 68
16. I got 43-45 what grade would that be?
17. would anyone like to take a guess at what 51/60 would be as ums? thanks
18. (Original post by Dr. Django)
In the past 52 has been the A boundary. Raw marks are converted to UMS marks (/90) depending on how the cohort found the exam.

This basically maintains the proportion of people that get an A each year and stops people being disadvantaged if their exam was particuarly difficult.

Therefore, 49/60 which is indeed over 80% in raw marks MAY not be an A after UMS scaling if in general people found the paper slightly easier than average
I just want B grade to be 44/46 marks, all I want is a B on the paper. High B in unit 2 and get an A overall :/
19. (Original post by Hasslol)
I got 43-45 what grade would that be?
a C or if your lucky low B
20. (Original post by yodawg321)
I just want B grade to be 44/46 marks, all I want is a B on the paper. High B in unit 2 and get an A overall :/
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.

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