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Edexcel - Chemistry Unit 2 - 4 June 2013

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Reply 460

F1's Finest

Original post by amber206

Why is there no hydrogen bonding between molecules of ethoxyethane? (Jan 2009, MC Q8)

CH3CH2OCH2CH3

Because no hydrogen atom is directly bonded to either (fluorine, oxygen or nitrogen).

Reply 461

own

Original post by amber206

Why is there no hydrogen bonding between molecules of ethoxyethane? (Jan 2009, MC Q8)

CH3CH2OCH2CH3

Think about the structure, for hydrogen bonding to occur, hydrogen has to be bonded to a more electronegative element I.e. fluorine oxygen or nitrogen. Here in to molecule, hydrogen is only bonded to carbons which have very similar electronegativities. Because of hydrogen not being directly bonded to the oxygen, no hydrogen bonds form :smile:

hope that helps

Reply 462

Goods

Original post by own

hope that helps

It can form hydrogen bonds when dissolved in solvents (due to lone pairs on the central oxygen) however it cannot form hydrogen bonds with itself

Reply 463

amber206

If anyone has January 2009 CH02 to hand,
the balancing of the half-equation for the
reduction of dichromate ions?

The electron number is 6 - why is it not 12?

Reply 464

own

Original post by Goods

It can form hydrogen bonds when dissolved in solvents (due to lone pairs on the central oxygen) however it cannot form hydrogen bonds with itself

Yes. I'm not quite sure what your getting at? The question taking about between molecules of ethoxylethane, not solvents. :smile:

Reply 465

Miri321

I don't even know why I can't figure this out:The following reactions have been used in the chemical industry to make liquid and solid products, allowing any gaseous products to escape into the atmosphere:

A CH3OH(g) + CO(g) --> CH3COOH(l)

B CaCO3(s) --> CaO(s) + CO2(g)

C CH4(g) + 3Cl2(g) --> CHCl3(l) + 3HCl(g)

D CH2CH2(g) + Cl2(g) --> CH2ClCH2
Cl(l)
Which reaction causes the most immediate damage to the environment?

Reply 466

lob.dub

Anyones got jan 2013 paper unit 2??????

Reply 467

kevsamuel

Did anyone do the June Unit 1 paper? And if so how did you find it and has anyone made an unofficial mark scheme for it?

Reply 468

Khurc003

Anyone know this one?? :/

13 When solutions of iodine are titrated with aqueous sodium thiosulfate solution, Na2S2O3(aq),
the thiosulfate ions are oxidized to

A S2O4

B S2O6

C S2O8

D S4O6

all of these options are 2-

(edited 10 years ago)

Reply 469

lob.dub

Original post by Miri321

hmmmmm....i think it shud b C as HCL gas is produced which is a steamy fume so obviously the mst immediate effect cud b dat........though i;m little vague abt it... :erm:

Reply 470

Khurc003

Original post by kevsamuel

Did anyone do the June Unit 1 paper? And if so how did you find it and has anyone made an unofficial mark scheme for it?

I did that! it was a retake and i thought it was less harder than jan but still difficult... and ive been looking for the unofficial mark scheme as well... no luck so far

Reply 471

username969261

Original post by lob.dub

Anyones got jan 2013 paper unit 2??????

http://www.thestudentroom.co.uk/showthread.php?t=2212573&page=10

"Weaslemoose" posted two PDF's here.

Reply 472

F1's Finest

Original post by Miri321

Either B or C.

B produces CO2 but C produces HCl.

They clearly say 'most immediate effect' so I would go with HCl because it could acidify rivers and kill fish. CO2 on the other hand is a greenhouse gas and it takes time before it rises up into the atmosphere and traps heat energy emitted from the earth.

Reply 473

kevsamuel

Original post by Khurc003

I did that! it was a retake and i thought it was less harder than jan but still difficult... and ive been looking for the unofficial mark scheme as well... no luck so far

Yeah, mine was a retake too as I got a C the first time round. I thought that it was easier than January too. But hopefully the grade boundaries will be at most about 63 for an A! (and that's pushing it...)

Reply 474

Polish master

Original post by amber206

If anyone has January 2009 CH02 to hand,
the balancing of the half-equation for the
reduction of dichromate ions?

The electron number is 6 - why is it not 12?

Dichromate has 2 chromiums at +6 and you are reducing it to Cr3+ to go from from 6 to 3 it is a gain of 3 electrons. Because there are 2 Cr's in dichromate you have to reduce both of them. therefore you needing 6 in total which equates to 3 electrons for each of the chromium's. hope that makes sense :smile:

I'm resiting and doing the later units really helps with the earlier stuff.

Reply 475

Khurc003

Original post by kevsamuel

yh that is pushing it.... lol I managed to scrap a B but right now im sooooo worried about unit 2 though :frown:

timing is a big issue

Reply 476

Khurc003

Someone pleeeeasee help with this one

When solutions of iodine are titrated with aqueous sodium thiosulfate solution, Na2S2O3(aq),
the thiosulfate ions are oxidized to

A S2O4

B S2O6

C S2O8

D S4O6

all of these options are 2-

Reply 477

posthumus

Original post by James A

Insanely stupid question.... does the atmosphere count as the environment ? :colondollar:

I mean would you consider a factory and the atmosphere as being in the same environment.

Also D won't react with the ozone will it ? only if it had a fluorine atom attached to one of the carbons it would? If so, do we need to know why this is..

Thanks :smile:

Reply 478

maryam1996

Hi, Can someone please explain to me why chlorofluorocarbons are no longer used as fire retardants and why we use hydrocarbons and why doesn't it break down in the stratosphere?
Thanks

Reply 479