Lurkers, register with SgForums and ask ur H2 Chem qns here!
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this qn came out in 2006 p2 qn 2e
and
2010 p3 qn 5e
https://www.dropbox.com/s/cd7ixziplyy6y3x/20160926_180400.jpg?dl=0
would u accept cs toh's answer(would u mark it correct)? instead of, or an additional point to the more complex answer of CuI precipitating discussed in Sgforums and in made easy inorganic book
https://www.dropbox.com/s/0fb9ue4ng4xsord/20160926_180413-1.jpg?dl=0
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pls look at my 2 qns at the btm of page 67 too, thank you !
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amide cannot be formed between carboxylic acid and amine right?
https://www.dropbox.com/s/h4xc7lpf2r5xcgh/20160926_182157.jpg?dl=0
https://www.dropbox.com/s/pb0hom468wft4kf/20160926_182206.jpg?dl=0
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2006 p3 qn 3
https://www.dropbox.com/s/n5545rg8gj6fiyj/20160926_184014.jpg?dl=0
https://www.dropbox.com/s/33jr12rs6io7pa2/20160926_184020.jpg?dl=0
how u know, and why is the rate of forward reaction small compared to the reverse reaction?? is it becos qn say 'the two gases react slowly'?
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https://www.dropbox.com/s/6ebkwa8la584e8e/20160926_185432-1.jpg?dl=0
small +ve E°value means redox reaction does occur, but is it occurs very slowly, or extent of forward reaction is very small, or both?
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Originally posted by Flying grenade:
the number of optical isomers in this molecule is 2^3 ?
is there a pair of cistrans isomer as well? i.e. 1 cis and 1 trans isomer
Yes lah. Simple qns like this u can't settle by urself meh? -
Originally posted by Flying grenade:
what in the world is the yellow brown ppt??
https://www.dropbox.com/s/7oymrgijg8ok4kk/20160926_180017.jpg?dl=0
http://forums.sgclub.com/singapore/cuso4_ki_407273.html
this one only have brown soln due to I3- ions
Haiz... white ppt of CuI(s) mixed with yellow-brown I2(aq) / I3-(aq) ions = (looks like) yellow-brown ppt lor. -
Originally posted by Flying grenade:
this qn came out in 2006 p2 qn 2e
and
2010 p3 qn 5e
https://www.dropbox.com/s/cd7ixziplyy6y3x/20160926_180400.jpg?dl=0
would u accept cs toh's answer(would u mark it correct)? instead of, or an additional point to the more complex answer of CuI precipitating discussed in Sgforums and in made easy inorganic book
https://www.dropbox.com/s/0fb9ue4ng4xsord/20160926_180413-1.jpg?dl=0
CS Toh's answer is fine. If in doubt, just write the basic answer first, then add on if you wish (and you think Cambridge may be asking for it). Be independently exam-smart lah. -
Originally posted by Flying grenade:
amide cannot be formed between carboxylic acid and amine right?
https://www.dropbox.com/s/h4xc7lpf2r5xcgh/20160926_182157.jpg?dl=0
https://www.dropbox.com/s/pb0hom468wft4kf/20160926_182206.jpg?dl=0
Whether can or cannot, depends on your reagents and conditions. Obviously in your human body, your enzymes make it possible, or you would already have died liao (if you're already dead but you don't know it, you're known as a psychotic post-mortem, ie. psychologically unstable after death). -
Originally posted by Flying grenade:
2006 p3 qn 3
https://www.dropbox.com/s/n5545rg8gj6fiyj/20160926_184014.jpg?dl=0
https://www.dropbox.com/s/33jr12rs6io7pa2/20160926_184020.jpg?dl=0
how u know, and why is the rate of forward reaction small compared to the reverse reaction?? is it becos qn say 'the two gases react slowly'?
Obviously lah. -
is there I2 formed ? I2 is black solid right?
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Originally posted by Flying grenade:
https://www.dropbox.com/s/6ebkwa8la584e8e/20160926_185432-1.jpg?dl=0
small +ve E°value means redox reaction does occur, but is it occurs very slowly, or extent of forward reaction is very small, or both?
Both, but more directly & reliably about thermodynamics + equilibrium, less directly & reliably about kinetics. If Cambridge asks, focus on the thermodynamics + equilibrium, and bring in kinetics only if the question suggests for it. -
oh yea i2 dissolved in soln containing I-
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Originally posted by Flying grenade:
is there I2 formed ? I2 is black solid right?
In the presence of excess I- nucleophile, nucleophilic addition occurs unto the I2 electrophile to generate the brown I3-(aq) ion. With non-polar solvents, the I3- dissociates back into colorless I-(aq) and purple I2 (solvated) / I2 (hexane) / I2 (CCl4).
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Originally posted by Flying grenade:
oh yea i2 dissolved in soln containing I-
Yes u coconaden, can u figure out urself properly first, dun keep wasting my time typing out, then after I post, turns out u subsequently posted a "oh yeah I know liao" a few sec later, eh dun waste my time lah! -
oh yeah i2(aq) is yellow brown color
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if cambridge asks for the meaning of
small -vedeltaG°or small+veE°cell
what we write for both?
for equilibrium, we just say extent of forward reaction is small, and position of equilibrium lies a little( as opposed to lie significantly) to the right ?
for thermodynamics write what??just say reaction is thermodynamically favourable?
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Originally posted by UltimaOnline:
In the presence of excess I- nucleophile, nucleophilic addition occurs unto the I2 electrophile to generate the brown I3-(aq) ion. With non-polar solvents, the I3- dissociates back into colorless I-(aq) and purple I2 (solvated) / I2 (hexane) / I2 (CCl4).how is it possible iodine dissolve in waterH2O to form brown soln? it shld be I2(s) in H2O right? or only extremely small amnts of I2 dissolve to form brown I2(aq)?
I3- is brown right?
how do we know the color or I2(aq) anyway? I2(aq) doesn't exist or exist very minimally?
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large -vedeltaG°or large+veE°cell means extent of reaction is very much complete? and position of eqm lies very much to the right?
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Originally posted by Flying grenade:
if cambridge asks for the meaning of
small -vedeltaG°or small+veE°cell
what we write for both?
for equilibrium, we just say extent of forward reaction is small, and position of equilibrium lies a little( as opposed to lie significantly) to the right ?
for thermodynamics write what??just say reaction is thermodynamically favourable?
Yes lah, it's common sense aint it?Stop asking these self-indulgent self-created questions, and stick to asking about TYS or Prelim paper questions and their given solutions. If this was a specific TYS or Prelim paper question, then ask me what is it about the given answer that you don't understand.
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Originally posted by UltimaOnline:
In the presence of excess I- nucleophile, nucleophilic addition occurs unto the I2 electrophile to generate the brown I3-(aq) ion. With non-polar solvents, the I3- dissociates back into colorless I-(aq) and purple I2 (solvated) / I2 (hexane) / I2 (CCl4).oh KI(aq)
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Originally posted by Flying grenade:
how is it possible iodine dissolve in waterH2O to form brown soln? it shld be I2(s) in H2O right? or only extremely small amnts of I2 dissolve to form brown I2(aq)?
I3- is brown right?
how do we know the color or I2(aq) anyway? I2(aq) doesn't exist or exist very minimally?
U coconaden. I've covered this so many times liao. U go figure out urself, or ask ur school teacher or private tutor. Don't waste my time. -
yes ok figured this out alr
https://en.m.wikipedia.org/wiki/Dehydrohalogenation
Dehydrohalogenation is an chemical reactionthat involves removal of (elimination of) ahydrogen halide from a substrate. The reaction is usually associated with the synthesis of alkenes
also in 2006 p3 qn 6a
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https://www.dropbox.com/s/dgaj5ka3tq5mimb/20160926_215830.jpg?dl=0
should x be 120, y be 107, z be 109°?
https://www.dropbox.com/s/bi2y9k6pgb4n7q6/20160926_215835.jpg?dl=0
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Originally posted by Flying grenade:
https://www.dropbox.com/s/dgaj5ka3tq5mimb/20160926_215830.jpg?dl=0
should x be 120, y be 107, z be 109°?
https://www.dropbox.com/s/bi2y9k6pgb4n7q6/20160926_215835.jpg?dl=0
I told u how many times liao, MCQ choose the best answer amongst the options lah, even if it's not totally correct.