Debrief - 9746 Chemistry
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it was in my h2 chem notes on carboxylic derivatives although explicitly labelled out of h2 syllabus. needed to know it cos er an olympiad question was also on this mechanism (ester formation).Originally posted by th3m0ment:so how am i supposed to know that?
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expected it to appear in your chem notes. same for other top schools too.Originally posted by teraexa:it was in my h2 chem notes on carboxylic derivatives although explicitly labelled out of h2 syllabus. needed to know it cos er an olympiad question was also on this mechanism (ester formation).
my sch's chem notes just give the minimal.
EVEN the tollen's reagent they only give "silver mirror seen"
I HATE MY SCHOOL! -
dun worry..my notes did the same too..just talk abt silver mirror for tollens' nth else..n it is a top school fyi..Originally posted by striderz_o405:expected it to appear in your chem notes. same for other top schools too.
my sch's chem notes just give the minimal.
EVEN the tollen's reagent they only give "silver mirror seen"
I HATE MY SCHOOL! -
or maybe it's just rj chem dept that's super kiasu. everything also dump into the notes.Originally posted by xxxshadowxxx:dun worry..my notes did the same too..just talk abt silver mirror for tollens' nth else..n it is a top school fyi..
i dun blame them though. best group of chem teachers i have seen. ever. -
yup..i haf heard of rj's pro-ness in chem..i tink for my sch the physics dept is good..u have some good n some bad..haha..tts life..just lyk today's econs paper..hahaOriginally posted by teraexa:or maybe it's just rj chem dept that's super kiasu. everything also dump into the notes.
i dun blame them though. best group of chem teachers i have seen. ever. -
Haha ... I almost panicked at that one.Originally posted by maxtonian:that is why the question states " SUGGEST the mechanism" ma. cos not in our syllabus.
Ok ... 1 mark gone out of 60, one is that decomposition answer (I go put neutralisation
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1 mark gone only?
everybody also 1 mark gone only?
everybodi here chem super kiang onez izit? dun come here make pplz scared lehz -
haha. no worries la. this forum how many ppl taking h2 chem nia. i'am sure there's alot of students out there who will commit careless mistakes one. ( including me. lol)
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Actually, more than a mark la, if that "ang mor buay song" my explanation... I know I was feeling severely feverish that day that I went out to the toliet to throw out just as I finish the paper in about 1 hour.Originally posted by th3m0ment:1 mark gone only? everybody also 1 mark gone only?
everybodi here chem super kiang onez izit? dun come here make pplz scared lehz -
MCQ was easy.
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easy meh?!?! i felt that some questions are hard lor...
wth is potassium hexacyanoferrate anyway? qn 36 the compound.. -
retarded moron post all answers you can remember please
got one like no answer leh?
MgCl2 + water --> Mg(OH)Cl + HCl
2AlCl3 + water --> Al203 + 6HCl
PCl5 + 4water --> H3PO4 + 5HCl
SiCl4 + 4water --> SiO2. 2H2O + 4HCl
answer where?
all the salt questions. acidic here basic there i catch no ball? which compound is got most dipole?
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K4[Fe(CN)6], if I'm not wrong. The Fe2+ can be oxidised by oxygen in air.Originally posted by akinos:easy meh?!?! i felt that some questions are hard lor...
wth is potassium hexacyanoferrate anyway? qn 36 the compound.. -
MgCl2 + 6H2O --> [Mg(H2O)6]2+ + 2Cl-Originally posted by th3m0ment:retarded moron post all answers you can remember please
got one like no answer leh?
MgCl2 + water --> Mg(OH)Cl + HCl
2AlCl3 + water --> Al203 + 6HCl
PCl5 + 4water --> H3PO4 + 5HCl
SiCl4 + 4water --> SiO2. 2H2O + 4HCl
answer where?
all the salt questions. acidic here basic there i catch no ball? which compound is got most dipole?
[Mg(H2O)6]2+ + H2O --> [Mg(H2O)5(OH)]+ + H3O+ (source of H+; multiple hydrolysis possible)
Therefore one mole of MgCl2 produces 2 moles of HCl.
Compound with the most net dipole is propanone. -
mm..i dont think the mcq ppr was easy at all...
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wat did question 36 ask about. which compound stable or not stable?
why not the ClCOCl thing for most dipole? since Cl withdraw electron then make the carbon more positive charged? -
er u do a vector sum. propanone will have a greater resultant dipole.Originally posted by th3m0ment:wat did question 36 ask about. which compound stable or not stable?
why not the ClCOCl thing for most dipole? since Cl withdraw electron then make the carbon more positive charged? -
wat about all those salt qn. can somebodi post some ans?
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hmmm is it about the MgCl2 being soluble or not?Originally posted by th3m0ment:wat about all those salt qn. can somebodi post some ans?
'dissolves in water, pH 6.5 -
got some add water, then form weakly acidic stuff then remove water get back salt that one
another one is about the CFC? -
er should be the carboxylate salt. the choice is between the phenol and carboxylate salt, but the carboxylate salt is less alkaline than phenol salt.Originally posted by th3m0ment:got some add water, then form weakly acidic stuff then remove water get back salt that one
another one is about the CFC?
for the dissolve in water to get the most acidic solution, it is the phenylamine salt because it is the weakest base and hence its conjugate salt is the most acidic.
CFC qn is the butane cos the others all can form radicals that destroy ozone. -
potassium hexacyanoferrate(III) is K3[Fe(CN)6]. that one is stable as oxygen cannot oxidise the salt.Originally posted by RETARDED_MORON:K4[Fe(CN)6], if I'm not wrong. The Fe2+ can be oxidised by oxygen in air.
as for the second one i am not too sure as they never say it's acidic medium although oxygen can oxidise it to cr3+.
the third one is definitely unstable as fe2+ can react with oxygen to form the oh- ions. -
can sumbodi roughly gauge wat the moderation and stuff will be like?
i'm afraid i wont get to pass chem...
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relax.. everyone is feeling as crappy as youOriginally posted by th3m0ment:can sumbodi roughly gauge wat the moderation and stuff will be like?
i'm afraid i wont get to pass chem...
its really above the usual standard of difficulty in my opinion, especially p3 -
PHEW. I changed the answer for that question at the very last minute to D.Originally posted by teraexa:potassium hexacyanoferrate(III) is K3[Fe(CN)6]. that one is stable as oxygen cannot oxidise the salt.
as for the second one i am not too sure as they never say it's acidic medium although oxygen can oxidise it to cr3+.
the third one is definitely unstable as fe2+ can react with oxygen to form the oh- ions.
bloody hell... i thought the question was talking about unstable -.- and went to shade C initially.