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Ocr f321 23 may 2013~official discussion thread

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thanks peeps for answers :biggrin:
Original post by FlyingGiraffe
Just a quick question plz!
What is a Precipitation reaction and how do you tell if it is one?
Good luck everyone :wink:


Precipitation reactions are group 7, you add silver nitrate to a solution containing halide ions and the colour of the precipitate tells you which halide is present
Chloride ions-white precipitate
Bromide ions-cream precip
Iodide ions-Pale yellow precip
Hope this helps, good luck!!
Original post by FlyingGiraffe
Just a quick question plz!
What is a Precipitation reaction and how do you tell if it is one?
Good luck everyone :wink:


Precipitation reactions are basically the ones you are using for your Silver Nitrate Tests so:

Ag+ + Cl- --> AgCl(s) Producing a white ppt Soluble in dilute ammonia
Original post by theCreator
Definitely think it will be a harder exam than usual. Don't know if you've taken any of these or heard, but all the maths, further maths, biology and physics exams so far have been considerably harder than previous years. We'll see tomorow morning though :smile:

Ahh right, not great news :s-smilie: thanks, good luck!
I get really confused with orbitals, sub shells etc
Does an orbital have 2 electrons? and a Subshell is the S, P, D and F?
Original post by theCreator
Nah sorry mate that's wrong. If the molecule is polar, and you just said the dipoles cancel out, how is the molecule polar? :smile:


Omg so sorry! I just realised my mistake haha :smile: thanks :smile: good luck for tomorrow
Original post by Char_lotteee
I get really confused with orbitals, sub shells etc
Does an orbital have 2 electrons? and a Subshell is the S, P, D and F?


I like to think of it as

Orbital = has 2 electrons with opposite spins ( 2px 2py 2pz)

Sub-Shell = S = 1 orbital, P = 3 orbitals, D, = 5 orbitals , F = 7 orbitals

Shell 1st = 1 sub-shell 2nd = 2 sub shells 3rd = 3 sub-shells 4th = 4 sub-shells
Reply 307
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avoxgirl
Original post by flyylikejetz
So if you had I2 to 2Br- it won't react but with cyclohexane the organic solvent will be purple because of the I2 ??


yeah. if they ask a question on it it will highly likely be in a table where you ust have to write the colour cyclohexane goes, or a 5 mark qu about reactivity of halogens and a test to show it
Original post by flyylikejetz
I like to think of it as

Orbital = has 2 electrons with opposite spins ( 2px 2py 2pz)

Sub-Shell = S = 1 orbital, P = 3 orbitals, D, = 5 orbitals , F = 7 orbitals

Shell 1st = 1 sub-shell 2nd = 2 sub shells 3rd = 3 sub-shells 4th = 4 sub-shells

Thank you so much! that makes so much sense now... good luck tomorrow!
Reply 309
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zangorou
Do we need to know in detail the history of the atomic model and the history of the periodic table?
How do you know if an element is diatomic ?


Posted from TSR Mobile
So what are the predictions for tomorrow? Any certain topics you guys think will appear in the exam?
Reply 312
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Daniel__
General question, in regards to systematic naming how do you know which element the roman numerals refers to as a rule of thumb? Also, can the roman numerals represent a negative oxidation number?
Original post by zangorou
Do we need to know in detail the history of the atomic model and the history of the periodic table?


No as it says they won't test us on it in the exam in a little examiners tip on the first spread.
what definitions do we need to know?
http://quizlet.com/23659907/f321-flash-cards/

Check this out, really helpful, someone posted it below
Reply 316
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sladyy96
Original post by krishkmistry
How do you know if an element is diatomic ?


Posted from TSR Mobile

Just remember H F Br O N I Cl - "HF Bronicle". As far as I know those are the only ones (only ones we were taught).
Original post by krishkmistry
How do you know if an element is diatomic ?


Posted from TSR Mobile



It's only diatomic in if it's a group 6, 7 element and nitrogen in group 5. Since they can get their full shells by bonding with each other, whether it be a single, double or triple bond.
Reply 318
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sladyy96
Does anyone know if we have to know how Carbonic Acid is formed (plus equations)?
Reply 319
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JimmyA*
5
Original post by MathsNerd1
So what are the predictions for tomorrow? Any certain topics you guys think will appear in the exam?

I'm guessing they'll put a hard titration type question, as the January report say's all the maths questions were answered very well and were too easy.

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