Soccerboi's questions thread

[soccerboi]

In HPLC and GC, which phase, stationary or mobile, is polar and which is non polar? How do we know or would it be given in the question?

And also, if both phases are the same, i.e both polar or both non polar, then there would be no separation right? as the sample under analysis would be equally attracted to both phases and thus would not move.

[charmanderp]

There's two types of chromatography; normal phase and reverse phase. The former consists of a polar stationary phase and a non-polar mobile phase, whilst the latter is to the contrary.

Normally they'll specify what exactly the mobile phase and stationary phase are. But if not, assume it's normal phase.

[Zahta]

why did tsfx say we should assume reverse phase ? is this in all types of chromatography? thanks just confused which one to assume.

[charmanderp]

To be honest just don't assume anything. I'm pretty sure that normal phase is, well, normal, but do whatever you can to deduce it from the question.

[Tonychet2]

why did tsfx say we should assume reverse phase ? is this in all types of chromatography? thanks just confused which one to assume.

they wouldnt have, maybe u misinterpreted ?? u always assume normal phase

[soccerboi]

1. Name the spectroscopic method which is most useful for the analysis of zinc content of foods.
-AAS, but would UV vis also be accepted as an answer?

2. Can someone explain why particles with highest mz values will be deflected least by the magnetic field?

3. If there was an strong acid in the burette and you accidentally washed the burette with a strong base, neutralisation occurs, but would the acid in the burette be more or less concentrated? Explain.

4. Does the term 'transesterification' mean the same as esterification/condensation?

5. Can we get from ethane to ethanol in 1 step, through substitution with water? or must we substitute Cl2 then NaOH?

[soccerboi]

In a 1.00 L vessel, 600 mL of chlorine gas, Cl2, is added to 400 mL of a saturated hydrocarbon that contains two carbon atoms. The vessel is then subjected to UV light for a period of time.

Assuming constant temperature and pressure, what volume is produced of the largest product?

Answer is 400ml, can someone show me how they got this?

[soccerboi]

When writing the semi structural formula for the fragment formed on a mass spectrum, when do we need to put the square brackets around it?
e.g [CH3CH2]⁺

Also, if anyone can help me with any of the questions above this post, it would be much appreciated 

[IndefatigableLover]

In a 1.00 L vessel, 600 mL of chlorine gas, Cl2, is added to 400 mL of a saturated hydrocarbon that contains two carbon atoms. The vessel is then subjected to UV light for a period of time.

Assuming constant temperature and pressure, what volume is produced of the largest product?

Answer is 400ml, can someone show me how they got this?

Mod edit: link to copyright material removed

Have a look at this and see if you get it from there
(Q4. Short Answer)

[pi]

Please do not post links to and/or upload and/or request copyright material on the forum (copyright by Insight, in this case)

[IndefatigableLover]

Please do not post links to and/or upload and/or request copyright material on the forum (copyright by Insight, in this case)

Hehe woops forgot about copyrighted materials :S

[Tonychet2]

When writing the semi structural formula for the fragment formed on a mass spectrum, when do we need to put the square brackets around it?
e.g [CH3CH2]⁺

Also, if anyone can help me with any of the questions above this post, it would be much appreciated 

square brackets arent required but any time a fragment is formed on the mass spectrum it can have brackets around it followed by a + sign,  [M]+ is the same as M+

just dont put it on when the question asks what fragment must be lost

[Tonychet2]

1. Name the spectroscopic method which is most useful for the analysis of zinc content of foods.
-AAS, but would UV vis also be accepted as an answer?

2. Can someone explain why particles with highest mz values will be deflected least by the magnetic field?

3. If there was an strong acid in the burette and you accidentally washed the burette with a strong base, neutralisation occurs, but would the acid in the burette be more or less concentrated? Explain.

4. Does the term 'transesterification' mean the same as esterification/condensation?

5. Can we get from ethane to ethanol in 1 step, through substitution with water? or must we substitute Cl2 then NaOH?

1. zinc is a metal so aas is more suitable
2.  the lightest ions are deflected the most and increasing m/z values would mean higher molecular mass
3. less concentrated, the final amount of acid in the burette would be lower then original
4. not sure
5. must go to cl2 then naoh but ethene can go to ethanol through water

[soccerboi]

1. Name the spectroscopic method which is most useful for the analysis of zinc content of foods.
-AAS, but would UV vis also be accepted as an answer?

2. Can someone explain why particles with highest mz values will be deflected least by the magnetic field?

3. If there was an strong acid in the burette and you accidentally washed the burette with a strong base, neutralisation occurs, but would the acid in the burette be more or less concentrated? Explain.

4. Does the term 'transesterification' mean the same as esterification/condensation?

5. Can we get from ethane to ethanol in 1 step, through substitution with water? or must we substitute Cl2 then NaOH?

1. zinc is a metal so aas is more suitable
2.  the lightest ions are deflected the most and increasing m/z values would mean higher molecular mass
3. less concentrated, the final amount of acid in the burette would be lower then original
4. not sure
5. must go to cl2 then naoh but ethene can go to ethanol through water

Thanks
Also, with question 3, i don't understand why the acid in the burette would become less concentrated, can someone elaborate on this?

[stephanieteddy]

It would be less concentrated because the total volume of the acid solution increases through the addition of the base. Higher volume, with same amount will give a lower concentration.