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Ocr f321 23 may 2013~official discussion thread

Reply 400

supernova99

6

Original post by aa05

hey guys can someone please post the january 2013 paper and markscheme? :smile:

Here you go :smile:

F321-01Jan13.pdf215.4KB

F321_MS_Jan13.pdf122.0KB

Reply 401

WorkingDodo

Original post by k1rby

Nitrogen is in the 5th group and so forms a 5+ ion. Copper has a variable oxidation state (along with the other transition metals) so don't rely on it always being 2+ :smile:

I thought Nitrogen formed 3- ions (azide ions)

Reply 402

Kitnimohabbathai

HELP WITH QUESTION 4Bii from the January 2011 paper!!! calculate conc. of HYDROXIDE IONS...ok so that's released from H20...double moles to get 0.00262moles...isn't that in 100cm3? so to find out how much in 1m3 should you multiply that by 10?

Reply 403

Geronimo!

7

Original post by Freddy-Francis

Na2S2O3

O = -2 -2 -2 = -6
Na = +1 +1 = +2
Therefore S = +2 +2

Sulphur = +2

then why isnt it +4 :confused:

Reply 404

megan1096

Original post by Kitnimohabbathai

guys help!!!!!!! question 3di from the may 2010 paper!?!! table on ionisation energies for aluminium...which ionisation energies represent removing electron from s subshell???? still have four past papers left :frown:

To make it easier you should write out the electrical configuration of aluminium which is 1s2,2s2,2p6,3s2,3p1

From here, you can work out which ionisation energies involve taking an electron from the S subshell.

The first is taken from the p subshell.
But the 2nd and 3rd electron are taken from the 3s2 subshell, so this is the 2nd and third ionisation energy.

Then 6 electrons are taken from the p subshell
The next electrons taken from the 2s2 subshells will be the 10th and 11th electrons and so the 10th and 11th ionisation energies.

Hope this helps :smile:

Reply 405

aa05

Original post by supernova99

Here you go :smile:

thankyou!

Reply 406

Kitnimohabbathai

Original post by WorkingDodo

I thought Nitrogen formed 3- ions (azide ions)

I thought nitrogen wasn't always +5?

Reply 407

Legal drugdealer

Guys chemistry has pretty much the same paper layout every year do you think its going to change this year like biology did?

Reply 408

supernova99

6

Original post by Kitnimohabbathai

HELP WITH QUESTION 4Bii from the January 2011 paper!!! calculate conc. of HYDROXIDE IONS...ok so that's released from H20...double moles to get 0.00262moles...isn't that in 100cm3? so to find out how much in 1m3 should you multiply that by 10?

You divide 0.00262 moles by 0.25 dm3

Reply 409

Kitnimohabbathai

thank you soo much :smile:

one thing im finding confusing....why do you count from the end? I started counting from 1s2,2s2...so I thought it would be the 1st and 2nd?

Reply 410

yodawg321

12

Please god let me get 45+ marks pleaseee

Reply 411

k1rby

10

Original post by WorkingDodo

I thought Nitrogen formed 3- ions (azide ions)

When it's in a nitrate ion (NO3-) it has a 5+ oxidation state always but when it's in ammonia (NH3) it is 3-. So it does usually but you'll need to remember when it isn't :smile:

(edited 10 years ago)

Reply 412

supernova99

6

Original post by Legal drugdealer

Guys chemistry has pretty much the same paper layout every year do you think its going to change this year like biology did?

To be honest i don't think there is much more that they could change so drastically but they may put little things in that they know people always get wrong.

Reply 413

megan1096

Original post by Kitnimohabbathai

thank you soo much :smile:

one thing im finding confusing....why do you count from the end? I started counting from 1s2,2s2...so I thought it would be the 1st and 2nd?

If you think about it like this... (how I think about it)

The electrons are removed from the furthest outer electrons in the outer sub shells first, and so the last subshells would be the first ones the electrons would be removed from, as they are the furthest away from the nucleus.

Reply 414

yodawg321

12

Original post by Legal drugdealer

Guys chemistry has pretty much the same paper layout every year do you think its going to change this year like biology did?

Probably, Biology and Physics changed a lot :frown:

Reply 415

Legal drugdealer

Original post by supernova99

To be honest i don't think there is much more that they could change so drastically but they may put little things in that they know people always get wrong.

Yh i guess but i think they might put more questions about applying our knowledge like biology.

Reply 416

supernova99

6

Original post by Legal drugdealer

Yh i guess but i think they might put more questions about applying our knowledge like biology.

Yeah they might do :s-smilie:

I guess we'll find out tomorrow morning!

Reply 417

JimmyA*

5

Do any of you agree, that the mark schemes for the ionisation energy and boiling/melting point questions seems really inconsistent? Some you get a mark for talking about the atomic radii, some you don't. The same with the nuclear pull aswell, it's silly.

Reply 418

supernova99

6

Original post by JimmyA*

Do any of you agree, that the mark schemes for the ionisation energy and boiling/melting point questions seems really inconsistent? Some you get a mark for talking about the atomic radii, some you don't. The same with the nuclear pull aswell, it's silly.

I do agree, it is annoying. I tend to write about number of shells, shielding effect and atomic radii just in case they decide to take one out of the mark scheme this year!

Reply 419

flyylikejetz

11

Obscure definitions they may throw at us!

Amount of Substance A quantity whose unit is the mole, used as a means to count No. of atoms
Mole Unit amount of a substance with as many particles as there are in 12g of a carbon-12 atom
Molecular formula The actual number of atoms of each element in a molecule
Concentration Amount of solute, in mole, per 1dm3 of solution
Concentrated High amount of solute per 1dm3 of solution
Dilute Low amount of solute per 1dm3 of solution

Just a lil heads up, probably won't come up but since people are saying this exam is going to be harder than usual... never know!

Good luck :smile:

Ocr f321 23 may 2013~official discussion thread

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