Answers To Difficult Questions (1 Viewer)

[elseany]

what was the multiple choice answer for the combustion one?

i put carbon dioxide cause i thought thats always a product and was hoping on the technicality that technically its not water thats formed but steam or something lol

 

[dwatt]

Here's what I got

So2 = 2.3L
chloride = 1.82 by ten to the four ppm (3 sig fig wasn't it?)
volume KOH = 3mL
Indicator = red to violet


I chose cl radical as a cataylst because BOS chose to show it being reformed. From what i remember initiators can be consumed in reactions.

Kicking myself over the whole "why can't you flame test". You COULD flame test it (and deduce that the only sample left was HCl). Saying that lead is toxic seems like the answer they are after.

 

[Forbidden.]

Sorry to burst the bubble but I think the dilution question was c)

It asks how much needs to be ADDED which is 810ml since we already have 90ml
Not the final volume which was 900ml.

I thought so.
Now I'm wrong.

It's either 1 or 0 marks.
I get 0 marks not even for working out , damn multiple choice.

 

[dwatt]

"what was the multiple choice answer for the combustion one?

i put carbon dioxide cause i thought thats always a product and was hoping on the technicality that technically its not water thats formed but steam or something lol"

Carbon dioxide is not necessarily always a product. Incomplete combustion can give you CO and C. But hydrogen is always present to be oxidised, and is most stable as H20 (so water is the only product you will always get)

 

[Forbidden.]

"what was the multiple choice answer for the combustion one?

i put carbon dioxide cause i thought thats always a product and was hoping on the technicality that technically its not water thats formed but steam or something lol"

Carbon dioxide is not necessarily always a product. Incomplete combustion can give you CO and C. But hydrogen is always present to be oxidised, and is most stable as H20 (so water is the only product you will always get)

A friend picked Carbon Dioxide as he neglected that incomplete combustions occur in this world lol.

 

[Forbidden.]

yeah its true about the catalysts... i cant remmeber where i read it. but either in esterification or hydration, the sulfuric acid actually attaches to form ethyl something or other, but then is reformed at the end

The purpose of sulfuric acid as a catalyst is it removes water from the reaction and according to Le Chatelier's principle it will force the reaction to the right.

 

[joshuajspence]

The purpose of sulfuric acid as a catalyst is it removes water from the reaction and according to Le Chatelier's principle it will force the reaction to the right.

it is also required to initiate the reaction as it removes hydrogen from the carboxylic acid and hydroxy group from the alcohol

 

[alcheikh]

The notes my teacher put up on the board for us say that Cl acts as a catalyst in breaking down ozone so that's why I put that basically.. heh

Well I got a completely different number to you but it had 5 digits and I'm expecting to get 0 for that question. I never understood ppm.

i put initiator because catalysts arnt incorporated into any reaction,
Cl* + O3 > O2 + OCl
thats y i thought it was an initiator but i could b rong

 

[sarang1703]

yeah agree the answer shud be water not carbon dioxide for the combusion one... i got the catalyst in ozone wrong though also the haber process mcq.
shud get 13/15 in mcq. i so wanst prepared for that scientist question, so had to make sum bullshit up about an analysical chemist, lol, shud get me 2/3...
as for the S)2 one im pretty sure its 2.32 litres now...
the NAHCO3 5 marker question stuffed me up tho... hant read up on that, wrote that it was a buffer rather than amphiprotic, but i also drew the equatios to say that it can neutralise both acids n bases so shud get sum marks eh??
and chlorine one, the smart bastards had replaced the sulfate content prac with the chlorine one, got 17500 ppm maybe its right, who knows!
neways glad chems ouuta the way now so preparing for maths... shit thats gonna be bad especially 3unit...
lol wrote an essay i think,
cheers guys

 

[sarang1703]

yeah agree the answer shud be water not carbon dioxide for the combusion one... i got the catalyst in ozone wrong though also the haber process mcq.
shud get 13/15 in mcq. i so wanst prepared for that scientist question, so had to make sum bullshit up about an analysical chemist, lol, shud get me 2/3...
as for the S02 one im pretty sure its 2.32 litres now...
the NAHCO3 5 marker question stuffed me up tho... hant read up on that, wrote that it was a buffer rather than amphiprotic, but i also drew the equatios to say that it can neutralise both acids n bases so shud get sum marks eh??
and chlorine one, the smart bastards had replaced the sulfate content prac with the chlorine one, got 17500 ppm maybe its right, who knows!
neways glad chems ouuta the way now so preparing for maths... shit thats gonna be bad especially 3unit...
lol wrote an essay i think,
cheers guys

 

[mitchbazza]

SO after trolling the whole of this thread my two cents are:

i got 2.32 for the S02.

and the 18050 for the other

and i belive the KOH required is 6ml.. i think many of you forgot that H2SO4 is diprotic.. correct me if uve already considered that in the answer u got as 3ml.

I also realise now i got 14 and 9 wrong from multiple choice.. and looking back 9's so obvious and my answer for 14 was due to a question misread.. damn!

good luck with the rest of the exams lads

 

[joshuajspence]

SO after trolling the whole of this thread my two cents are:

i got 2.32 for the S02.

and the 18050 for the other

and i belive the KOH required is 6ml.. i think many of you forgot that H2SO4 is diprotic.. correct me if uve already considered that in the answer u got as 3ml.

I also realise now i got 14 and 9 wrong from multiple choice.. and looking back 9's so obvious and my answer for 14 was due to a question misread.. damn!

good luck with the rest of the exams lads

we already considered it being diprotic. it is 3mL

 

[mitchbazza]

Oh what did you put for question 6.??

 

[Armenikum]

its definitely not a
i don't think its c cause it says "white light" should be "light of a specific wavelength"
probably is d

plus the silly mistake i made in the exam should get 13/15 in multi choice

Argh 14 was so vague.

From Pathways,

If WHITE light is passed through an atomic vapour at a suitably low temperature to prevent electron excitation, some WAVELENGTHS are selectively ABSORBED and dark lines appear in the spectrum produced. These dark lines correspond to the exact bright line wavelengths in AES"

Suggesting C, but also D coz of the spectral lines corresponding to the wavelenghts.

 

[dwatt]

As far as the KOH question, people shouldn't have to double their answer as long as they wrote a balanced eqn. From the reaction, it was possible to see that 2 moles of KOH are required to neutralise one mole of H2S04 (same thing really).

The dilute sample of H2SO4 was 0.0005 M (i think). So...0.010 M of KOH was required. Then I used v=n/c and 3mL of KOH was required.

 

[Armenikum]

It also says further into it ,

"The light source in the spectrophotometer is usually a hollow-cathode lamp of the element that is being measured. Thus if the concentration of copper in a water sample is to be determined, the lamp uses a copper cathode. This lamp generates wavelengths of light specific to the element being analysed".

Go figure.

Im thinking they use DIFFERENT lamps, which make the atoms absorb certain wavelenghts of the white light being emitted. I could be over complicating it as well

I think at this point in time, you can say the answer was E, it wont change what the markers will agree on as the answer.

 

[Armenikum]

Was the combustion answer int he multiple choice water?

I put Carbon Dioxide.
​

 

[tad2115]

Cl* is best described as a catalyst.

As there is a natural equilibrium in the stratosphere of destruction and formation of ozone. The Cl* merely speeds up the destruction of ozone as so eloquently stated in one of the neap past paper marking criteria.

 

[chris1189]

I got 18050 or something

ME TOO!!!!

 

[Cookie182]

Modeliing Equilibrium for Industrial- Loved that q

who used he N204 <> 2NO2 + heat system??

talk about change from colourless to brown wit temp. changes

wasnt sure about the limitation though?