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OCR Chemistry F322~ 4th June 2013~ AS Chemistry

ugh this exam is terrible , it like throws half the things you learn from the books out the window by asking so many questions in unfamiliar circumstances.

Reply 561

ImAz

6

Do we need to know a mechanism for the hydration of an alkene?

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Reply 562

Jimmy20002012

OP

4

Original post by ImAz

Do we need to know a mechanism for the hydration of an alkene?

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Not the actual mechanism, but need to know for example a molecule formed if hydrogen is added :smile:

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Reply 563

needtosucceed=)

10

Original post by Jimmy20002012

Not the actual mechanism, but need to know for example a molecule formed if hydrogen is added :smile:

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isnt hydration when steams added to make an alcohol

Reply 564

Gotzz

13

Original post by needtosucceed=)

isnt hydration when steams added to make an alcohol

Yes, the other person described hydrogenation.

Reply 565

ImAz

6

Original post by Jimmy20002012

Not the actual mechanism, but need to know for example a molecule formed if hydrogen is added :smile:

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I meant the reaction with steam in the presence of H3PO4 catalyst, 300•C and 60 ATM

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Reply 566

needtosucceed=)

10

Original post by ImAz

I meant the reaction with steam in the presence of H3PO4 catalyst, 300•C and 60 ATM

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yea you dont need to know the mechanism, just how to write an equation representing it :smile:

Reply 567

niceguy95

14

Original post by ImAz

Do we need to know a mechanism for the hydration of an alkene?

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Hydration using:
steam
Phosphoric acid
300c
60 atm
Producing only ethanol

C2h4 +h2o(g) ------> c2h5oh

Reply 568

Jimmy20002012

OP

4

Original post by Gotzz

Yes, the other person described hydrogenation.

Ohh did I explain hydrogenation? :smile:

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Reply 569

Gotzz

13

Original post by Jimmy20002012

Ohh did I explain hydrogenation? :smile:

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Yup, you said adding hydrogen.

Reply 570

ImAz

6

Thanks guys!

Another question, how would you all go about discussing the processing of waste polymers? Eg separating, recycling, combusting and cracking? I'm struggling to summarise it

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Reply 571

Munrot07

18

If anyone wants some help with chemistry I would recommend my youtube channel that does OCR bio and chem vids :smile:

people seem to like them and I want to help. I have upload 4 more videos today :smile:

http://www.youtube.com/user/MrBioTom1

Reply 572

RachHill

1

Can someone please explain fragmentation and mass spectrometry...it confuses me so much!!!

Reply 573

needtosucceed=)

10

Original post by RachHill

Can someone please explain fragmentation and mass spectrometry...it confuses me so much!!!

in a mass spectrum the peak furthest to the right is called the molecular ion peak, its m/z is equal to the molecular mass of the compound. all the other peaks may correspond to the possible fragments a molecule can split up into.
so for example if you had ch3ch2ch2oh...the possible fragment ions could be ch3+, ch3ch2+ (or c2h5+) ch2oh+, basically u just split the molecule up whereever possible. these fragment ions would appear on a mass spectrum by their molecular masses. so for example on a mass spectrum there could be a peak at m/z=15, showing a ch3+ ion present (12+3=15), or if there was a ch2oh in a compound, the spectrum would show a peak at m/z=31.
the main thing to remember is when given a long 10 marker on identifying compounds, use the molecular ion peak on the spectrum so you know the molecular mass of the compound. then if you know the empirical formula, which you've most likely worked out in the question already, you can work out the molecular formula hence helping to determine the structure of the compound.
one thing to note is, although i said the peak furthest to the right is the molecular mass, if theres a tinyyy little peak next to it on the right then ignore it, its the taller peak thats the molecular ion peak.
the other thing is uses of mass spec, which include mars space probes, breathalysers and pollution.

Reply 574

yodawg321

12

Original post by needtosucceed=)

in a mass spectrum the peak furthest to the right is called the molecular ion peak, its m/z is equal to the molecular mass of the compound. all the other peaks may correspond to the possible fragments a molecule can split up into.
so for example if you had ch3ch2ch2oh...the possible fragment ions could be ch3+, ch3ch2+ (or c2h5+) ch2oh+, basically u just split the molecule up whereever possible. these fragment ions would appear on a mass spectrum by their molecular masses. so for example on a mass spectrum there could be a peak at m/z=15, showing a ch3+ ion present (12+3=15), or if there was a ch2oh in a compound, the spectrum would show a peak at m/z=31.
the main thing to remember is when given a long 10 marker on identifying compounds, use the molecular ion peak on the spectrum so you know the molecular mass of the compound. then if you know the empirical formula, which you've most likely worked out in the question already, you can work out the molecular formula hence helping to determine the structure of the compound.
one thing to note is, although i said the peak furthest to the right is the molecular mass, if theres a tinyyy little peak next to it on the right then ignore it, its the taller peak thats the molecular ion peak.
the other thing is uses of mass spec, which include mars space probes, breathalysers and pollution.

That was beautiful.

Reply 575

needtosucceed=)

10

Original post by ImAz

Thanks guys!

Another question, how would you all go about discussing the processing of waste polymers? Eg separating, recycling, combusting and cracking? I'm struggling to summarise it

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what you've written is pretty much the answer. most questions just ask you to state/describe how to dispose of them and advantages and disadvantages to them. so..
- sorting AND recycling. you have to say both these words. helps conserve supplies of crude oil which is a finite resource.
- incineration. benefits are that it reduces the need for landfill space which is in short supply, the process releases energy which can be used to heat the rest of the factory/for electricity/sold to the national grid. however they release toxic fumes eg. HCl(g), which can be reacted with bases or alkalis to neutralise them
- crack them, then use the products to make plastics
- use an chemical feedstock (i think?)

(edited 10 years ago)

Reply 576

needtosucceed=)

10

Original post by yodawg321

That was beautiful.

haha thanks! :smile:

Reply 577

Raju

Can someone upload the flash cards document which is in the Exam Cafe CD that comes with the ocr book please. Or send me a link to one that has been uploaded, because ive been looking on the net for ages and have had no luck finding it.

Reply 578

needtosucceed=)

10

Original post by Raju

Can someone upload the flash cards document which is in the Exam Cafe CD that comes with the ocr book please. Or send me a link to one that has been uploaded, because ive been looking on the net for ages and have had no luck finding it.

there you go. i've put some of the other files too :smile:

RES7_chemglossary (1).doc329.7KB

RES8_chemcontentchecklist (2).doc449.5KB

RES9_chemflashcards (1).doc148.0KB

RES12_chembookanswers (1).pdf249.6KB

RES17_chemexaminerstips (1).doc267.8KB

RES18_chemrypstretch.doc196.1KB

Reply 579

RachHill

1

Original post by needtosucceed=)

in a mass spectrum the peak furthest to the right is called the molecular ion peak, its m/z is equal to the molecular mass of the compound. all the other peaks may correspond to the possible fragments a molecule can split up into.
so for example if you had ch3ch2ch2oh...the possible fragment ions could be ch3+, ch3ch2+ (or c2h5+) ch2oh+, basically u just split the molecule up whereever possible. these fragment ions would appear on a mass spectrum by their molecular masses. so for example on a mass spectrum there could be a peak at m/z=15, showing a ch3+ ion present (12+3=15), or if there was a ch2oh in a compound, the spectrum would show a peak at m/z=31.
the main thing to remember is when given a long 10 marker on identifying compounds, use the molecular ion peak on the spectrum so you know the molecular mass of the compound. then if you know the empirical formula, which you've most likely worked out in the question already, you can work out the molecular formula hence helping to determine the structure of the compound.
one thing to note is, although i said the peak furthest to the right is the molecular mass, if theres a tinyyy little peak next to it on the right then ignore it, its the taller peak thats the molecular ion peak.
the other thing is uses of mass spec, which include mars space probes, breathalysers and pollution.

thank you this makes so much sense

OCR Chemistry F322~ 4th June 2013~ AS Chemistry

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