2016 A Level H2 Chemistry Paper 2, 3, 1 discussions

last SG · 2016-11-08T20:10:45+00:00

I would think they should accept only NO2+S02=SO3+NO then regeneration bla bla blaso its like a homogeneous catalyst and Oxidising agent i would think elect...

Thomas00 SG

I find that the paper is straightforward. But i lost marks in Q3 deductive. The rest are pretty ok.

Zhhh_ SG

Hey ultima. If i wrote wrong state symbol for Q5 last part, for eg. I wrote PCl5 as liquid and HBr as liquid too, would i lose both marks? Also earlier in Q5 i wrote PCl5 without state symbol for the formation of RCl from ROH as i was unsure will i also lose the mark? What are the marking points for VSEPR theory?

Overall I find the paper simpler than Paper 2, which was a really weird paper.

Thefire521 SG

I find that the paper is straightforward. But i lost marks in Q3 deductive. The rest are pretty ok.

Did you guys remember to distill away the alcohol after forming ur r-cl?

UltimaOnline SG

Just to add : in case anyone is looking for full solutions, I won’t be providing them here ; many Singapore JCs’ Chem departments will be preparing the solutions, as well as several private tutors and tuition centers, who will probably upload their solutions in pdf format on their tuition websites or google drive or scribd, etc. You can look for the solutions online yourself, or ask your school teachers if your school’s Chem dept will be providing the full answers.

UltimaOnline SG

Overall I find the paper simpler than Paper 2, which was a really weird paper.

No worries about state symbols.

For VSEPR theory, only 2 marks, so just give any 2 of the more important points (I can think of 5 points).

https://en.wikipedia.org/wiki/VSEPR_theory

houdini_00 SG

What i did was i completed half of q3. But saw the long deduction question so i just continued with q4 and q5 they were finished in arnd 30 minutes. Why did you not move on to try the rest?

I had around fifteen minutes left to attempt Q4 and give up on Q3 . But I thought I might try to queeze one to two marks out of Q3 because I've already secured ten marks there. I thought I barely had time to secure equivalent marks for Q4. That's why. But i made up for the marks with other Questions thankfully.

lalalaboi998 SG

Is the question about voltage decrease due to no salt bridge?

Thomas00 SG

Did you guys remember to distill away the alcohol after forming ur r-cl?

Hi, are you referring to Q5? Didn't attempt it

UltimaOnline SG

Is the question about voltage decrease due to no salt bridge?

No.

It's about non-standard molarities as reaction progresses, [Zn2+] increasing, [Cu2+] decreasing, Le Chatelier's principle, less positive reduction potential for Cu2+/Cu, less positive oxidation potential for Zn/Zn2+, hence less positive Cell potential.

Thefire521 SG

Is the question about voltage decrease due to no salt bridge?

No.

Thefire521 SG

No.

Agreed. Was thinking this was the only point they actually tested equilbrium shifts ( i think) in the entire 2 papers.

Thomas00 SG

Luckily they didn't test buffers, pka graphs.

lalalaboi998 SG

Oh thnx thnx

Thefire521 SG

Luckily they didn't test buffers, pka graphs.

They totally ignored kinetics as well, which is peculiar.

Many of the questions were just simple write combustion rxns, write free radical rxns... compare reactivities, you just gotta follow instructions.. talk about clf3... standard q

DemonicTable SG

ArJoe SG

Hi for the last question, it is acidified kmno4, dry pcl5
then the second one is liquid bromine, excess concentrated nh3, heat in a sealed tube?

And for qn 3 the deduction, is it geometrical isomer and 4 isomers?

Thefire521 SG

Just curious, for the calculation of bond energy in 2(b), I carelessly drew the arrow for bond energy in the wrong direction hence obtaining negative answer. Will I be penalised fully in both parts of 2(b)?

Your part b i answer would have been wrong. part b ii was on entropy so its unrelated.

ArJoe SG

Same i drew the entire cycle correctly with the correct values but arrow in the wrong direction, will i get most of the marks?

Thomas00 SG

They totally ignored kinetics as well, which is peculiar.

Many of the questions were just simple write combustion rxns, write free radical rxns... compare reactivities, you just gotta follow instructions.. talk about clf3... standard q

Yup. Also not much protein chemistry although last year i think.

Thefire521 SG

Hi for the last question, it is acidified kmno4, dry pcl5
then the second one is liquid bromine, excess concentrated nh3, heat in a sealed tube?

And for qn 3 the deduction, is it geometrical isomer and 4 isomers?

Last Q5 should be oxidative cleavage, PCL5 s RT for steps 1 and 2

but your second one should not be using Br2 because you will get disub

You should be using HCL(g) or similar

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