Hi, for paper 3 qn 3civ) is it possible to say that the p orbitals containing lone pair of electrons on Cl overlaps with the pi orbitals of the c=c, thus causing partial double bond formation and making it hard for the C-Cl bond to break?
Thanks Ultima..
Oops i wrote wrongly about H2SO4 being used against I2, actually I meant H2SO4 being used against NaI, it would produce HI which would be further oxidised by H2SO4 to I2 which contaminates HI. But I think I carelessly wrote in my exam script that I is a stronger reducing agent than Cl, so maybe I would be deducted a mark for this?
For p3 q5, the effect of adding NH3 (before in excess) to Cu2+,
Its Cu2+ + 2OH- ---> Cu(OH)2 (reversible arrow), but if i didn't write the initial eqn of NH3 reacting with H2O to form OH-, will I be penalised?
And if i used LCP in the later part to explain why Cu(OH)2 ppt dissolves to form dark blue soln, but didnt use Ionic pdt < Ksp concept to explain why it dissolves, is it okay?
Thks!
Originally posted by student1996:Hi, for paper 3 qn 3civ) is it possible to say that the p orbitals containing lone pair of electrons on Cl overlaps with the pi orbitals of the c=c, thus causing partial double bond formation and making it hard for the C-Cl bond to break?
Originally posted by moonwalkers:Thanks Ultima..
Oops i wrote wrongly about H2SO4 being used against I2, actually I meant H2SO4 being used against NaI, it would produce HI which would be further oxidised by H2SO4 to I2 which contaminates HI. But I think I carelessly wrote in my exam script that I is a stronger reducing agent than Cl, so maybe I would be deducted a mark for this?
For p3 q5, the effect of adding NH3 (before in excess) to Cu2+,
Its Cu2+ + 2OH- ---> Cu(OH)2 (reversible arrow), but if i didn't write the initial eqn of NH3 reacting with H2O to form OH-, will I be penalised?
And if i used LCP in the later part to explain why Cu(OH)2 ppt dissolves to form dark blue soln, but didnt use Ionic pdt < Ksp concept to explain why it dissolves, is it okay?
Thks!
Kk thanks!
Can I know why you think the cut off for A last year was 75%?
And do you think its possible for me to get an A this year if i got a range between 72-75%?
Originally posted by moonwalkers:Kk thanks!
Can I know why you think the cut off for A last year was 75%?
And do you think its possible for me to get an A this year if i got a range between 72-75%?
Originally posted by Kingweixian:Can I ask what’s the answer for 2a, 2b and 2ci for p3
cos I not sure if I correct a not
hello, could someone could give me a weightage or rough weightage for each paper?
so far what i know is that planning is 5%, SPA is 15%.. so how would p1,2,3 fit the remaining 80%?
this comes after much regretted paper 3 during which my mind went blank upon seeing weird qns like heating LiAlH4 would make it a stronger reducing agent etc... i might not have done so well for that :X
so.. id love to know how much paper 3 would have screwed my overall score over so i can better prepare myself for how much p2 and 1 can pull me up..
hi
if for qn 2b) i quoted -116.5 as -117 (3sf) as final answer, will deduct?
A Level Chemistry Paper 2 Planning Practice : http://twig.sg/facebook/Paper 2 Planning.pdf
Originally posted by Alohamadda:hi
if for qn 2b) i quoted -116.5 as -117 (3sf) as final answer, will deduct?
Originally posted by littledragon:hello, could someone could give me a weightage or rough weightage for each paper?
so far what i know is that planning is 5%, SPA is 15%.. so how would p1,2,3 fit the remaining 80%?
this comes after much regretted paper 3 during which my mind went blank upon seeing weird qns like heating LiAlH4 would make it a stronger reducing agent etc... i might not have done so well for that :X
so.. id love to know how much paper 3 would have screwed my overall score over so i can better prepare myself for how much p2 and 1 can pull me up..
Does anybody know the national average for distinction for last year chem paper?
Ultima, roughly how many % of students in SG gets an A every year?
Completed paper 1 in 30 mins.
I really want to check my answers, anyone!!?
Originally posted by Kingweixian:For qn 28 what is the identity of the white ppt formed in Option C
When u use dilute nitric acid, i think there might be possible multiple substituitions resulting in white ppt. So i dunnoe whether d is correct orwrong.
And qn 20, why not D?
Originally posted by Alohamadda:When u use dilute nitric acid, i think there might be possible multiple substituitions resulting in white ppt. So i dunnoe whether d is correct orwrong.
And qn 20, why not D?
Hmm, counting that in i got 27/40... Haiz b alr
Could u draw them structures out? I triied drawing it agn but still got 6 lol
Thx sir
Sir, What will be the cutoff for A and B this year based on the difficulties of the papers?