more questions

[Glockmeister]

Ah ok, thanks Mao

[shinny]

basically if theres an excess of Cl, the reaction of C-H bonds breaking and C-Cl bonds forming will just keep going up to tetrachloro. wording for the question isnt too great since they dont mention excess, but i would assume D as well given what u have

[bec]

If you had to label functional groups, would you call C=C an alkene functional group?

Also, when you draw a polypeptide, should the ends of the amino acids be NH2 and COOH, or NH3+ and COO-? or does it depend on whether the question states that it's in zwitterion form? or...is zwitterion form sort of "negated" when they form dipeptide bonds?

[Mao]

If you had to label functional groups, would you call C=C an alkene functional group?

VCAA did it in the sample exam, and since we live in VCE land for everything that happens, yes, VCAA accepts it [as for if it is an actual functional group, that is not part of the VCE course ]

Also, when you draw a polypeptide, should the ends of the amino acids be NH2 and COOH, or NH3+ and COO-? or does it depend on whether the question states that it's in zwitterion form? or...is zwitterion form sort of "negated" when they form dipeptide bonds?

i've only ever seen it draw with NH₂ and COOH. unless the question states the polypeptide is in zwitterion form, i'd take the safer option.

though my personal opinion on this [probably wrong] is that polypeptides dont often go into zwitterion form. Zwitterion is when the COOH donates the H to the NH₂ [remembering that both are weak acid/bases]. In an 2-amino acid, the distance between them is short, so the proton can move with a degree of ease. In a polypeptide, however, the chain is very long, and it'll be very difficult for the proton to travel that far. Since the weakness of both functional groups, a portion will ionise with water, but the majority will stay in the neutral form [not zwitterion]
[just my take, could be completely wrong]

[bec]

how would we show the equation for hydrolysis of glycogen into glucose?

would that just be (C₆H₁₀O₅)_n + nH₂O --> nC₆H₁₂O₆?

[chem-nerd]

how would we show the equation for hydrolysis of glycogen into glucose?

would that just be (C₆H₁₀O₅)_n + nH₂O --> nC₆H₁₂O₆?

n-1(H20)

[bec]

ah yep you're right
so otherwise is that ok?

[bec]

also, just found something in my textbook that i don't understand...mass spec:
The relative intensities of the ions depend on:
- the energy of the bombarding electrons how would we know how energetic the electrons are?
- the stability of the ion fragments formed what constitutes a stable fragment?
- the ease with which ions can lose atoms how can we know this

Or, do you think we'd just not need to know any of it...is it enough to just know that fragments have different intensities, for a variety of reasons, and the height of the peak corresponds to its intensity/relative concentration?

[Mao]

also, just found something in my textbook that i don't understand...mass spec:
The relative intensities of the ions depend on:
- the energy of the bombarding electrons how would we know how energetic the electrons are?
- the stability of the ion fragments formed what constitutes a stable fragment?
- the ease with which ions can lose atoms how can we know this

Or, do you think we'd just not need to know any of it...is it enough to just know that fragments have different intensities, for a variety of reasons, and the height of the peak corresponds to its intensity/relative concentration?

we dont mean to know these, but just remember that some things are easier broken than others

like, O-H is broken easier than O-O, C-C is fairly easy to break, C=O almost never happens, etc~

[bec]

alright sounds good

what about the synchrotron...i'm assuming we don't need to know about that?

[Mao]

alright sounds good

what about the synchrotron...i'm assuming we don't need to know about that?

absolutely not

that's physics unit 4 detailed study xD

[bec]

last question:

The ammonia content of one window cleaner is given as 4.0% NH3 (m/V)
A 750mL of this cleaner would contain approximately
A. 1.8 mol of N atoms
B. 30mL of NH3
(+ some other options)

i thought both of these were correct?
the answer is A, but couldn't you assume that the density of NH3 is ~1g/mL, so since there's 30g NH3 in 750mL of the solution, that'd be approx 30mL NH3?

[Mao]

yes, that *could* be assumed, but some NH3 will also ionise to form NH4+, so its not exact.

A however, is correct.

[bec]

in carboxylic acids, do you always start counting the carbons (for naming purposes) from the end with the carboxyl group, regardless of where functional groups are attached?

also, i have a few qs from exam 3 in the neap book

Q7 multiple choice
have no idea what this is...

4c
...how would you know that Cr2+ is going to be oxidised to Cr3+ when added to MnO4- ...in hindsight it seems obvious, but originally i assumed it would just form an Cr(MnO4)₂. if the question doesn't specifically state it's going to be redox, is there any way of knowing that it is - except using intuition and the fact that the permanganate ion is a strong oxidant?

thanks

[shinny]

7. just identify each linkage and put a line to cut where the bond forms. in this, its obviously an ester link, so cut a line between each OO and ull begin to obviously see that the square is a diol and the triangle is a...di...carboxylic acid thingy...forgot what their actual name is =P

4c. u wouldnt actually need to state it gets oxidised to Cr3+, but ull have to say that it may react with the MnO4- whereas it wouldnt have any effect in colorimetry/UV vis because it doesnt react with the ferrozine. the word 'suggest' in the question kind of implies that ull have to make a few assumptions here (such as that it doesnt react with ferrozine)