2012 O-Level Pure Chemistry Paper 2 Questions and Answers

ksosk

Rayner 发表于 9-11-2012 16:42
Got Physics One haha, Very tough paper

Nope, the Physics was incomplete

Maryguttak

Hi, will I be able to get the marks for the qns below? A million thanks!
Q3a(ii) Heat produced by lightning activities caused nitrogen in air and oxygen in air to react, producing nitrogen oxides.
Q3c(ii) CO2 is a greenhouse gas, and it will enhance greenhouse effect, worsening global warming.
Q6b(i) Density = Mass/Volume, hence it is dependent on not only molar mass and also volume. The difference in volume of bromine n chlorine may account for the difference in densities
Q6b(ii) They have difference relative molecular mass.
Q6c(i) Diatomic refers the the covalent bonding between two similar halogens chemically combined.
Q7c(ii) If I have forgotten to x25% to the mass of brine, but all my methods are simultaneously accurate, will I get the method mark?

ksosk

For
3a(ii) Yes you will have the marks.

3c(ii) In my class, your answer is considered incomplete! So, I would say zero. But you just may have it based on cambridge's leniency.

6b(i) You have only one focus in your answer - volume difference. For that you should have 1M.

6c(ii) Halogen is used wrongly here! No marks.

7c(ii) Yes there's error carried forward but no marks for answer. Hence, overall 1M.

Maryguttak

ksosk 发表于 11-11-2012 01:11
For
3a(ii) Yes you will have the marks.

Thank you! You have missed out Q6b(ii) :) Btw, for this paper, how would you, in your opinion, rate students that are of A1 calibre? >70marks? Thanks!

ksosk

Maryguttak 发表于 11-11-2012 14:12
Thank you! You have missed out Q6b(ii)  Btw, for this paper, how would you, in your opinion, rat ...

My bad, but I would say no to your answer to 6b(ii). Hint given is g/cm3 and Mr is use for mol/cm3 =(

Yes, I would say close to 70 for A1. However, it is just a guessing game, no one can be absolutely sure.