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Edexcel - Chemistry Unit 2 - 4 June 2013

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Can someone tell me the colours of Bromine gas, Bromine in aqueous solvent, and Bromine in hydrocarbon? Thanks.

Chlorine - colourless in both water and hexane (polar solvent)
Bromine - orange in water and orange in hexane (polar solvent).
Iodine - brown in water and violet in hexane (polar solvent)

Bromine as a gas is orangey/brown: https://www.google.com/search?site=&tbm=isch&source=hp&biw=1366&bih=675&q=bromine+gas&oq=bromine+gas&gs_l=img.3..0l5j0i5l2j0i24l3.232.1728.0.1821.13.12.1.0.0.0.253.1080.6j3j1.10.0...0.0...1ac.1.14.img.483-Psm4Ltk

Reply 201

zyxwvuts

Original post by HarryMWilliams

Thank you! Textbooks say different things, it's so confusing!

Reply 202

TheKingOfTSR

Is it a good and a better idea to do section b and c first and then the damned MCQs.
There will definitely be some difficult ones that one would leave for the end so why not do them at last. Also we could plan the time more effectively, doing section b & C in a hour and at most 70 mins...
:rolleyes:

What are your opinions? I tried it for UNIT 1 and I feel that I did well and better on the MCQs than otherwise
.

Reply 203

phaseshift

Original post by samsimmons

Thank you! Textbooks say different things, it's so confusing!

No worries.

Original post by TheKingOfTSR

What are your opinions? I tried it for UNIT 1 and I feel that I did well and better on the MCQs than otherwise
.

I would get them out of the way, if you dont get an MCQ, leave it and come back to it. But make sure you do come back to it and not completely forget like someone I know did.

Ideally, you would have 15 minutes after finishing the paper to go back through and read everything to make sure you've covered enough.

Reply 204

zyxwvuts

Original post by TheKingOfTSR

What are your opinions? I tried it for UNIT 1 and I feel that I did well and better on the MCQs than otherwise
.

But the MCQs are the best bit! Haha.
If it works for you, than you should do it!

Reply 205

Cattey watty

Thanks posthumous and ramanan, very helpful :biggrin:

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Reply 206

Baraf

Original post by rockstar101

Ok it is trigonal planar by the carbon atom forms 2 double bonds with two xygen atms and then the third oxygen provides its lone pair of electrons to form a dative bond thus the 2- value of co3 if im not wrong :smile:

hmmm, I dn't think carbon can have that many bonds lol

Reply 207

phaseshift

Original post by Baraf

hmmm, I dn't think carbon can have that many bonds lol

Carbon forms 4 covalent bonds - in carbon dioxide, the carbon is double-bonded to each oxygen atom, therefore, the oxygen atoms have two lone pairs each left over.

Reply 208

Baraf

Original post by HarryMWilliams

Carbon forms 4 covalent bonds - in carbon dioxide, the carbon is double-bonded to each oxygen atom, therefore, the oxygen atoms have two lone pairs each left over.

yes but can Carbon form two double bond with two oxygen and then on top of that a dative covalent bond with a third oxygen. ?

Reply 209

phaseshift

Original post by Baraf

yes but can Carbon form two double bond with two oxygen and then on top of that a dative covalent bond with a third oxygen. ?

I believe so, it's called carbontrioxide, although it's apparently very unstable.

Reply 210

wbrian

Original post by rockstar101

When it decomposes due to heat it produces co2 which makes the cake rise and soft. Lol. Dw

Agh I thought of it but then I thought it was wrong eventually ran out of time leaving it blank :frown:

how many marks was it ??? Thanks by the way :P

Reply 211

SKK94

In ozone depletion reactions, like NO + O3 --> NO2 + O2, is 'NO' a free radical?

Reply 212

zyxwvuts

Original post by SKK94

In ozone depletion reactions, like NO + O3 --> NO2 + O2, is 'NO' a free radical?

Usually they accept it as a radical and not as a radical.

Reply 213

F1's Finest

NO is a free radical. Sometimes in the exam they don't include the dot, just to confuse you.

Reply 214

rockstar101

Original post by wbrian

Agh I thought of it but then I thought it was wrong eventually ran out of time leaving it blank :frown:

how many marks was it ??? Thanks by the way :P

aww lol it was one mark so no stress. just conc on unit 2 now :smile:

Reply 215

Mollymod

Original post by posthumus

It was locked or something 4 days ago, but only for a couple of hours :redface:

How'd you find unit 1 ? :smile:

Oh right.

Sorry for the late response, I've been exhausted.
Last day at school last Friday and we had days of pure messing around. It was so fun all the pranks we played and just eating in the Chemistry labs and partying the same evening! Really took my mind off things but I need to get back to studying for Biology and German! Chemistry's on hold for about a week or two. (Although I know I'll wander back to it when I get bored)

Unit 1: I just felt like they were trying to make us apply our knowledge of trends to unfamiliar elements so I did have to do a little bit more thinking on the isotope questions, and then the Hess Cycle I definitely messed up, as well as the Calorimetry and percentage error. Essentially, the mathematical bits. I know the more familiar organic chemistry was absolutely fine. It'd annoy me if I made silly mistakes on that, because those are the bits I absolutely knew.

Multiple Choice was okay, but taxing on the mind to put in second electron affinity, but I put first electron affinity as exothermic in the end which seems to have been correct. I'm really terrible with Mean Bond Enthalpies, so I may well have lost 10 marks at minimum, more than that at maximum XD and I would really love high UMS, or as close to maximum as possible. If not, it's not the end of the world at all, it just means I have to be a boss at Unit 5 which isn't impossible, it's just a bit scary to put all your hope in the hardest paper :confused:

How did you find it?

Reply 216

SKK94

Original post by samsimmons

Usually they accept it as a radical and not as a radical.

Original post by James A

NO is a free radical. Sometimes in the exam they don't include the dot, just to confuse you.

Alright, thanks! :smile:

Reply 217

coolio41

Hey guys,

I was wondering if we could make a list of all the practicals we need to draw/ write about for unit 2, I should've done this for unit 1, as one of the questions I mucked up completely was the drawing the practical one -_- aha.... :/

Thanks in advance!

Reply 218

zyxwvuts