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AS Chemistry- helping each other out!

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Original post by cilla_e
Hi can you show me how to answer this question, i have no clue! (Its multiple choice btw)

1.40 g of an alkene gave 3.77 g of a dichloroalkane on reaction with chlorine.
What is the molecular formula of the alkene?

A C2H4

B C3H6

C C4H8

D C6H12

Thank you!


ImageUploadedByStudent Room1431868353.018236.jpg


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Original post by Mo_Jo.
Cobalt can you answer my question please


What question?


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Original post by C0balt


@Cobalt I love how your practically our online teacher :'D
Original post by annie79
@Cobalt I love how your practically our online teacher :'D


:colondollar:

Don't forget to give credit to others though! I do make mistakes and there are other very helpful people here who can correct me and have a deeper knowledge because I don't have any further knowledge than AS materials
I just happen to be online most of the time lol


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If anyone knows why option A in the question is the answer, pls let me know. and please note, the question asks to put a cross in the INCORRECT option.

chem unit 2 question.jpg


Also, someone pls tell me what the fingerprint region is O.o
Original post by annie79
If anyone knows why option A in the question is the answer, pls let me know. and please note, the question asks to put a cross in the INCORRECT option.

chem unit 2 question.jpg


Also, someone pls tell me what the fingerprint region is O.o


Fingerprint region is the region on the right hand side of the spectrum with so many complicated peaks and they are completely different for every compound so can be used to distinguish two compounds like butan-1-ol and butan-2-ol. They will have similar pattern on the left but completely different on the right.

So the two compounds in this question will have different fingerprint region.
The answer is A because the C=O peak is different in aldehyde and ketone I guess?

WAIT
don't they have same molecular ion peak in mass spectra? Are you sure it's not D
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(edited 8 years ago)
Xxx
Original post by 76584
I need the mark scheme for the f321 ocr A chemistry 2014 paper, does anyone have it please?


I have it somewhere... I'll try and find it for you later :h:

Original post by annie79

Also, someone pls tell me what the fingerprint region is O.o


The messy bit on the right hand side of the spectra, basically :yep:
It's usually from about 1500-500cm-1, and it contains a complicated series of absorptions, due to the bending vibrations within the molecule (think about how difficult it would be to pick out individual bonds from this part of the spectra, compared to the LHS). It's called the fingerprint region because every compound produces a unique pattern of troughs.

Hope this helps :smile:
Original post by C0balt
Fingerprint region is the region on the right hand side of the spectrum with so many complicated peaks and they are completely different for every compound so can be used to distinguish two compounds like butan-1-ol and butan-2-ol. They will have similar pattern on the left but completely different on the right.

So the two compounds in this question will have different fingerprint region.
The answer is A because the C=O peak is different in aldehyde and ketone I guess?

WAIT
don't they have same molecular ion peak in mass spectra?
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I'm pretty sure the answer is d as well. Especially since in a data booklet ketone stretch is at 1715 cm/s compared to 1720-1740cm/s for aldehyde. I'd say they're pretty similar

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Original post by samb1234
I'm pretty sure the answer is d as well. Especially since in a data booklet ketone stretch is at 1715 cm/s compared to 1720-1740cm/s for aldehyde. I'd say they're pretty similar

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I guess she has mistaken it with other question
Admittedly the multiple choice is hard to mark because they are so packed :lol:


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Can someone please please please give me the May 2014 unit 2 paper??? I desperately need it :'(
Original post by 123pickles
Need help with question 5(g) - AQA Unit 1 June 2013.

Which one of the first, second or third ionisations of thallium produces an ion with the election configuration [Xe] 5d10 6s1?

The answer is second - i understand why it is second but how can you to do without writing the whole configuration of thallium out as the question is only worth one mark.


Hi, Tl, thallium is in group 3 therefore it has 3 electrons in its outer S shell.
The config you got given said S1 so you know its second as it lost two :smile:
Original post by sagzy22
Can someone please please please give me the May 2014 unit 2 paper??? I desperately need it :'(


For AQA?
Original post by Neuth
I have it somewhere... I'll try and find it for you later :h:



The messy bit on the right hand side of the spectra, basically :yep:
It's usually from about 1500-500cm-1, and it contains a complicated series of absorptions, due to the bending vibrations within the molecule (think about how difficult it would be to pick out individual bonds from this part of the spectra, compared to the LHS). It's called the fingerprint region because every compound produces a unique pattern of troughs.

Hope this helps :smile:

Would you have the unit 2 paper june 2014? Because I really really need it.
Original post by samwillettsxxx
For AQA?


OCR
This is the JUNE 2014 unit 2 paper for OCR A
F322-01 Jun14.pdf510.9KB
Let me know if you'd like me to attach the mark scheme x
Original post by sagzy22
Can someone please please please give me the May 2014 unit 2 paper??? I desperately need it :'(


I've posted it
Original post by C0balt
I guess she has mistaken it with other question
Admittedly the multiple choice is hard to mark because they are so packed :lol:


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Here idgi
1431883903668-644612200.jpg518.4KB
Original post by Mo_Jo.
Here idgi


ImageUploadedByStudent Room1431884327.744867.jpg
Do you follow this?
X is the percentage abundance of 10 and there is only 11 so 11 must have abundance of 100-x %
You plug those into formula to find percentage abundance


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