CSSA Chemistry Trials (1 Viewer)

[bored of sc]

*Prays for 50%*

 

[shaon0]

For a monoprotic acid:
say the height was 2x starting
e.g. HCl --> H⁺ + Cl^-
wouldn't the height of the products be x respectively

For a diprotic acid:
let height be 3x starting
e.g. H₂SO₄ --> 2H⁺ + SO₄^2-
wouldn't height be 2x for H ions and x for SO4 ions

I only put the chart for monoprotic and only for 1st ionisation Not the second one as you can't really get an exact degree of ionisation for Sulfuric acid's 2nd partial ionisation.

 

[DannyT]

hmmm was that a two marker?
it just said strong acid and didn't specify monoprotic or diprotic?
i think the 50/50 one is safe but i duno lol

 

[kwabon]

i cannot believe i misread so many questions ...... *prays for 50%*, i am in the same boat as you, bored of SC

 

[Shoom]

Hi
For the acid model, say you did HCL

This goes HCL--> H+ + Cl-, the mole ratio is still 1:1:1, so the bars should be the same size, not half the original, I think..


either way I screwed that one up.


And how the hell do I change my stupid avatar?

 

[ratcher0071]

I only put the chart for monoprotic and only for 1st ionisation Not the second one as you can't really get an exact degree of ionisation for Sulfuric acid's 2nd partial ionisation.

That is true. Since the 2nd ionisation of Sufluric Acid is reversible. Anyway the qn only asked for a monoprotic acid.

Hi
For the acid model, say you did HCL

This goes HCL--> H+ + Cl-, the mole ratio is still 1:1:1, so the bars should be the same size, not half the original, I think..

In response to the acid qn:
If u looked at the example for the weak acid. Did u notice that the heights of the H₃O⁺ and the A^- added together to make the remaining height of the product HA

 

[spagbowl]

i think its a problem when people talk about questions and i have absolutly no memory of doing those questions. I finished the whole papaer its like i didn't pay attention which is a worry

 

[DannyT]

yeh that's true they did add up. i drew mine equal but not exactly half sized and not exactly big haha. damn i thought that it was simple.

 

[Shoom]

Damn two marks down the drain.


Sigh.

 

[David.Lai]

hey, no CO2 is a greenhouse friendly gas.

 

[ec23]

I didn't really find that ionisation one weird. The one with the table? We did one just like that in our half yearlies, and its in the syllabus.

i completely stuffed that one, what was the answer... i went blank!!

 

[annabackwards]

i completely stuffed that one, what was the answer... i went blank!!

Less concentration of HCl (i think that was the strong acid) is needed to get the same pH as as a higher concontration of acetic acid, because HCl is strong and completely disassociates whereas acetic acid is weak (since pH is based on concentration of H+)

The pH for the acetic acid solution went up when the sodium acetate was added because the sodium acetate further reacts with water for form hydroxide ions, causing the solution to become more basic. On the other hand, sodium chloride is a completely neutral salt which does not react further with water so the pH for the HCl solution did not change when NaCl was added

 

[ec23]

Less concentration of HCl (i think that was the strong acid) is needed to get the same pH as as a higher concontration of acetic acid, because HCl is strong and completely disassociates whereas acetic acid is weak (since pH is based on concentration of H+)

The pH for the acetic acid solution went up when the sodium acetate was added because the sodium acetate further reacts with water for form hydroxide ions, causing the solution to become more basic. On the other hand, sodium chloride is a completely neutral salt which does not react further with water so the pH for the HCl solution did not change when HCl was added

definitely didn't write that.

who did forensic
did you do AAS and mass spectroscopy for the analytical techniques... or hplc and glc

 

[clintmyster]

the joys of not having to do CSSA =] Hope you guys did well.

 

[RocKetBoy]

I screwd up option pretty bad =(
and the pH multiple choice i put D but it was actually to 3sig fig ithink...somethink lyk that o.0 that was a wierd question lol
um...i screwed up sulfate% calculation cos i divided by mass of precipitate instead of sample T.T stupid stupid STUPID >.<
I reckon i got low 80's, would be really happy if i can reach low 90's ^^:rofl2:

 

[lynton]

i found the multiple choice ok, the short answers were good except for the fertiliser one and i didnt finish industrial chemistry so there goes 12 marks woo for me!!

 

[Aquawhite]

My teacher makes us choose Industrial Chemistry as the elective next year -_- (eck)... I don't think I'll like it!

 

[Sarah182]

I thought it was a good paper, I felt pretty good about it afterwards which is surprising.
The only thing that were bad was the one about the radioisotopes question.
And the option was a bit like WTF? Our teacher altered the option because we haven't finished it and ended up putting in questions I didn't have a chance with...

 

[clintmyster]

when do you think the paper will be posted up? Im eager to look at it haha

 

[marinaghattas92]

i loved chem!!! it wasn't a hard exam n as sum1 else said u just had to study!!! quns weren't hard...except the isotopes one...i dnt give a s*&% which one decays!!!! it's not a maths exam....n its not lyk the syllabus dot points asks us to do that...anywaiiz...we'll live...once anyone get's their results can they start posting em up...coz i wanna compare 'with the rest of the state'..lol dats wat ma teacher said was the point of sitting this exam instead of him writing it...oh well...hope to hear from u soon my fellow chem peers!!!