General Thoughts - Chemistry (3 Viewers)

[jah_lu]

i rote
amphoprotic-2eq
solid-rather than liquid-can be contained
weak base-compared to naoh, can be used in excess
stable, can be stored

disadvantages-more expensive then sodium carbonate
than evaluation

 

[jhobbs]

Haha, nice one. Did you mean the Haber process one?

I thought the exam was pretty good, and I got most of the calculations.

Did everyone multiply by 2 in the Sulfuric acid one? (Because it's diprotic)

yeh, but if you mean the cabage question whats the diff on the level of ionisation of the second proton in the H2SO4. is it assumed to be complete and therefore pH 2 or incomplete and then ph higher.

 

[aja152]

im not confident with this exam T_T

my option topic (forensic chemistry) was easier than expected,
i was glad to see nothing on HPLC etc was in it, cuz i had no idea an didnt want to know.. i was disappointed that nothing on distinguishing test was in it, memorised it for nothing.
anywho,
the calculations and equation writing parts was terrible
especially question 17 and the sulfur question,

 

[aja152]

I agree with the first part.
I kept asking people at school and MSN, "Who didn't select Ethanol as their renewable resource ?"

Also, when they handed the exam papers to us before reading time, I could see through the first page and saw the first question, from then on I knew it was an easy exam.
Thanks BOS for thin and almost transparent papers, they look like someone's white T-shirt after they've been drenched, saturated, soaked and bombarded by water bombs .

ah~hahaha
nice one!!!

 

[Fish Sauce]

I had absolutely no idea about the NaHCO3 question, I didn't remember learning about it at all.

I did say that it was amphiprotic though which was a total guess but yay +1 mark

 

[mikietom]

all i want to know is if any one got the first multiple choice wrong if u got that wrong dont worry about how bad u are at chemistry u should get out from underneath the bridge ur living under the answer was A

 

[dwatt]

The bicarbonate ion ACTS as a buffer. It does this because it is amphiprotic.

I said the same as other ppl. Cheap/easy to store/ non-corrosive (so can be used in excess)/ does not spread like liquids / obtained as solid so easy to add.

 

[drynxz]

AHHH didnt like that exam one bit...so many stupid mistakes and now i look back on it i couldve done much better.
calculations were a bitch

i was so pissed at myself for getting the equlibrium constant wrong in industrial chem..

I wrote k= [0.5]^2/[0.75][0.5]^2 which was supposed to give u an answer of 1.33
but i typed o.25 in my calculator giving me an answer of 4 AHHH! ><

 

[k4t5UM0t0]

NaHCO3 is definitely not a buffer
buffer is a solution containing equimolar amounts of a weak acid and its conjugate base, that is able to maintain a constant pH when large amounts of acid or base are added.
Amphiprotic: a substance that can act as a bronsted lowry acid (i.e proton donor) and bronsted lowry base (i.e. proton acceptor)

NaHCO3 is cheap, easy to store, weak base, stops bubbling when neutralisation complete with an acid and easy to clean up after neutralisation. Preferable over dilution and neutralisation with strong acid or base.
However large amounts required for large spills

 

[jah_lu]

it forms a buffer with carbonic acid
i doubt you'd ever have carbonic acid lying around and theres no point in buffers to chemical spills
if you spilt sodium hydroxide, you dont want to keep the place basic

 

[dwatt]

NaHCO3 is definitely not a buffer
buffer is a solution containing equimolar amounts of a weak acid and its conjugate base, that is able to maintain a constant pH when large amounts of acid or base are added.
Amphiprotic: a substance that can act as a bronsted lowry acid (i.e proton donor) and bronsted lowry base (i.e. proton acceptor)

NaHCO3 is cheap, easy to store, weak base, stops bubbling when neutralisation complete with an acid and easy to clean up after neutralisation. Preferable over dilution and neutralisation with strong acid or base.
However large amounts required for large spills

Yeah, you're right. I wrote it small so hopefully they won't notice it.

 

[dejan1989]

i thought that the chem exam wasnt that bad surprisingly.

I may have possibly aced it!

 

[Originality]

NaHCO3 is amphiprotic. And y is it 5 marks!!!!!!!!!!!!!!!! i made up stuff.

I didnt like that exam.

 

[Fish Sauce]

NaHCO3 is amphiprotic.

I didnt like that exam.

I wish now that I had BSd more on that answer. I wrote that it was amphiprotic but honestly had no idea whether it was or not. I probably could have come up with something about why it's useful. Ah well.

 

[Omie Jay]

For that NaHCO3 question, for 5 marks, i wrote that it can neutralise acid spills and base spills, then equation of it reacting with H+ and OH-, then i also wrote that since its in powder form it is easier to clean up afterwards, than if it were in liquid form. I reckon theres the 5 marks for me.

 

[cc =)]

i screwed up that chem exam =(
it prob wont count for me cos i got 13 units =) but overall , it was easier than last year

 

[mzduxx2006]

as long as u wrote the structural formula..

omg funny thing is. i actually think i got that question right. holy fuk :S

 

[Golbez]

We had a guy leave the exam like an hour in...

He's been bottom of the class since yr 11 though

 

[noitall]

i had no funing idea how to do that question. i had never done an equilibrium question like that before and it completely through me off. who gives a shit. =) no more chemistry.

 

[BHHS]

Overall test was easy made 2 stupid mistakes AIYAH I think band 6 should be no problem 18000 PPM for chlorine WTF its worse than seawater lol