stonecold's chem questions :)

[stonecold]

lol that is freaky.  we are doing the same stuff haha!

okay, i'll remember to draw in the heights next time.
i was just a little confused because in the multi choice they try and trick you by giving you a really high peak, but as it does not have the biggest area, it isn't the most concentrated.

i'll probably go on to AoS 2 tomorrow, need to do other stuff now

[vexx]

lol that is freaky.  we are doing the same stuff haha!

okay, i'll remember to draw in the heights next time.
i was just a little confused because in the multi choice they try and trick you by giving you a really high peak, but as it does not have the biggest area, it isn't the most concentrated.

i'll probably go on to AoS 2 tomorrow, need to do other stuff now

yeah it would have a lower concentration but a high amount relative to the other substances.
im a bit confused too dw, because i thought in the spectroscopy interpretations that peak area= amount of substance ha but in this it's different.

[stonecold]

arghh that is so confusing.  so height means actual concentration, whilst peak area means amount present relative to other substances yeah?

edit: no, that can't be right, because in question 1.4.2, the one with the highest concentration is M, as it has the largest peak area.

[vexx]

arghh that is so confusing.  so height means actual concentration, whilst peak area means amount present relative to other substances yeah?

edit: no, that can't be right, because in question 1.4.2, the one with the highest concentration is M, as it has the largest peak area.

huh..
chromo:
peak height= relative amount
peak area= relative concentration

spectro:
peak height= absorbance
peak area= relative amount

[stonecold]

this may sound stupid, but what is the difference between relative concentration and relative amount?

Does it mean for example:
Say you analyse a mixture of 200mL 0.1M ethanol and 100mL 0.2M propanol.

Ethanol will have the greater peak height, and propanol will have the greater peak area.
is this right?  Sorry for the confusion!

[vexx]

this may sound stupid, but what is the difference between relative concentration and relative amount?

Does it mean for example:
Say you analyse a mixture of 200mL 0.1M ethanol and 100mL 0.2M propanol.

Ethanol will have the greater peak height, and propanol will have the greater peak area.
is this right?  Sorry for the confusion!

yeah i think so.
amount is literally how much you have, like in the examples 200mg is smaller then 700mg, where 700mg sample has a larger height.
and concentration is the amount per litre or whatever, MolL-1/gL-1, etc, and having 0.2M is a larger concentration, so it would have a larger peak area.

[stonecold]

okay, thanks vexx.  something finally clicked.

peak height = amount
peak area = conc.

[vexx]

okay, thanks vexx.  something finally clicked.

peak height = amount
peak area = conc.

no probs. hopefully this was all right! and its only for chromatography.

[stonecold]

This is from the 2007 Exam.

Which one of the following is least likely to be a product of a redox reaction between sulfuric acid and zinc metal?

A. H₂
B. H₂S
C. SO₂
D. SO₃

I have the answer, I just don't get why.  The Checkpoints explanation is vague.

[vexx]

Well.. A redox reaction involves a reduction of one and oxidation of the other reactant.

So the Sulfuric Acid has to change oxidation state, which means the sulfur does.
H2 is (pretty sure) the most likely product, Zn + H2S04 --> ZnS04 + H2 (as metal + acid --> salt + hydrogen gas)

With the other three just need to look at oxidation state changing for sulfur, which is +6 in H2S04
in H2S = S is -2
in S02 = S is +4
and S03 = S is +6, which is unlikely since the sulfur didn't change oxidation state, therefore no redox reaction occured..

Making the answer D. Is this correct?

[stonecold]

Yepp, thanks!

[stonecold]

How many different proton environments are there in:

CH₃CH₂COOCH₂CH₃   ?

[Blakhitman]

Four?

[simonhu81292]

4 . . .!!~
this question was from one of the exams ,.. right stonecold?

[stonecold]

Stupid spectroscopy, it is ruining my life!  

You guys are right.    and yeah its from, STAV 09 simon.

How do you know that the CH3 groups on either end are different?  They are both attached to CH2 so I thought that made them the same....