Chemistry - General Thoughts (1 Viewer)

[Tegwen]

a simple, straight forward chemistry exam - straight from the syllabus. raw marks will be high - will bring scaling down - way down

 

[punki_pixi]

What was the test for the lead ion in the water sample question?

 

[Bokky]

for the lead ion determination i said add iodide ions to the sample of water suspected of containing lead. if a yellow precipitate (PbI2) forms then lead ions are present in the solution

 

[Mz_mE]

could u have said aas to test for lead?

 

[punki_pixi]

oh no.. its coming back to me now but i could never remember those tests. I said to add HCl and PbCl2 ppt would form but I didn't think it would be right. I got desperate and wrote that if its in trace amounts AAS would be needed... lol thats 2 marks gone.

 

[thunderdax]

for the lead ion determination i said add iodide ions to the sample of water suspected of containing lead. if a yellow precipitate (PbI2) forms then lead ions are present in the solution

I second that.
Pretty easy test, 7 markers weren't too strenuous or hard to write about. It seemed really short to me but maybe I missed something out it was all a bit of a blur to me. To all you people feeling bad about the 90+ people, just remember markers pick apart long answers and most these people won't really get 90+ as their raw mark. I'm not putting them down, its just the way things are in science.

 

[punki_pixi]

Yeh I was happy with this test overall as well. I came out feeling better than I did for any other exam. I know i've definitely lost some marks and I'm sure that there were answers without enough detail but who actually aims for 100%? I want a band 6 and I'll be happy.

 

[bluebiro]

yeah it was a good test...i will still probably fail though

 

[yew_315]

Meh, not too bad....

I thought it was a pretty good test. Some weird questions in their that i found a bit curvey, but pretty good all round. I like the 7 mark questions, they were easy as so i should hopefully get full marks for those. Anyone who did biochemistry of movement, did you think it was pretty basic stuff? So, i hope i get around the low 80s to low 90s. Only two more to go!!! Modern History and Physics, here i come...

 

[Just James]

i'm disappointed there was no radio isotopes in it. but i think i did as good as i can expect, so i'm happy.

you're forgetting the very first multiple choice question, lol

 

[Casmira]

dry cell! I just had to make up some shit about the dangers of the NH4Cl, i didnt put any equations of reduction in it I forgot

 

[~ ReNcH ~]

AAS would be to test the concentration of lead ions once it is known that there are lead ions present, and the question addressed the latter. I just said to add NaOH, producing a white precipitate of Pb(OH)² in the presence of lead...hopefully it's correct.

Overall, I wouldn't say that exam was easy. In fact, no exam is easy per se. The calculations were slightly unusual imo, but doable. The MC was the most annoying and frustrating, because of the ambiguity of a couple of them. I was happy with the Shipwrecks question, and hopefully the only area in which I lose marks is the magnesium strip/iron nail question (if any). In general, less straight-forward than 2004, but then that's just my opinion

 

[Just James]

m/c

For q9, i picked (D) CH3COOH/CH3COO-, is that right?
For q15, i picked (A) 0.15, is that right?

 

[Just James]

AAS would be to test the concentration of lead ions once it is known that there are lead ions present, and the question addressed the latter. I just said to add NaOH, producing a white precipitate of Pb(OH)² in the presence of lead...hopefully it's correct.

It's actually KI. Pb reacts with KI to form yellow PbI(sub)2 precipitate.

 

[Rekkusu]

Hahh the dry cell was actually so easy, I was virtually writing my equations straight out of memory...

Aww darn though, why did they make it so easy..

 

[midnight_magick]

for the lead ion determination i said add iodide ions to the sample of water suspected of containing lead. if a yellow precipitate (PbI2) forms then lead ions are present in the solution

*cough*ocugh* i nearly choked on my food wen i read that. i wrote exactly the same thing except i made it up on the spot. i never studied the solubilty table or precipitation reactions. go me! lol

 

[bmc]

hmm i thought it was easy but 4 me that usually means i did crap. Wat was with the zn and gas graph. shouldnt volume b on the vertical axis yet there wasnt any room to fit it.oh well. i can always try again next year. yay acceleration

 

[bmc]

It's actually KI. Pb reacts with KI to form yellow PbI(sub)2 precipitate.

there is a heap of possibilities to test 4 lead. its from the cations flow chart in chem contexts 2 for any of u who have it. i had add dilute HCl then dilute NH3 to a secind sample to confirm its lead. but thats just one option. AAS is definalty not

 

[rama_v]

a simple, straight forward chemistry exam - straight from the syllabus. raw marks will be high - will bring scaling down - way down

Aligning and scaling are two separate procedures. Just because an exam is easy doesn't mean that its scaling will be low. Scaling is determined by how people in chemistry go in all of their other exams...If everyone who did chem did well in their other exams, then chem will still have great scaling

 

[Haku]

oh no.. its coming back to me now but i could never remember those tests. I said to add HCl and PbCl2 ppt would form but I didn't think it would be right. I got desperate and wrote that if its in trace amounts AAS would be needed... lol thats 2 marks gone.

for that i remembered dreamerish's thread on water quality. first u acidify the water, by adding HCl. then add Na2S, and a yellow precipitate would form if Pb is present