Lurkers, register with SgForums and ask ur H2 Chem qns here!
-
reduction of ester to alcohol?
-
nice
-
ok i think i get it. because for that particular compound, due to that particular structure, H2CO3 can be formed, so CO2 and H2O and NH4+ is formed for acidic hydrolysis, whereas CO32- and NH3 is formed during alkaline hydrolysis
for other amides that do not have that structure for the production of H2CO3, on acidic hydrolysis, just produce -COOH, and NH4+ . for alkaline hydrolysis, produces COO- and NH3
-
*ok understood alr. temp doesn't relate to enthalpy change
e.g. an exo rxn may still require input of energy (e.g. various organic rxns that require input of heat energy , doesn't mean they're endo)
doesnt mean endo rnxs require high temp
understand cambridge may give info and hints (sometimes they don't, e.g.
https://www.dropbox.com/s/wvvsxce2hkjff2j/20160927_200958.jpg?dl=0 . but ok, since we shld know rxn proceeds, so shld be exo)
if temp dont affect thermodynamics, then how does endothermic reactions proceed? (then cannot always use the guideline that rxn proceed, it is an exo rxn alr.)
i know need supply energy. e.g. solar energy from sun for photosynthesis(endo)
[endothermic rxns] how does autodissociation of water, and dissolving ammonium salt happens in nature? (does ammonium salt dissolves naturally? or need input of kinetic energy from stirring)
i have a confusion
i thought supplying heat energy(and hence an increase in temperature), helps an endothermic rxn proceed? ( just thought of this, oh yeah, it does, as predicted by LCP, eqm shifts to favor the endo rxn when heat is supplied to the system)
temp affects kinetics and equilibria
-
thiosulfate dot and cross
https://www.dropbox.com/s/6nsguwugbnu2lzk/20160930_110328-1.jpg?dl=0
from Wiki
some google images
-
my question : why is the bond between two sulfur atoms in S2O32- a single bond? isn't forming a double bond more thermodynamically favourable?
interestingly, the Resonance Hybrid in the wiki page shows S-S !!! why?? (i.e. no partial double bond between S atoms in the hybrid so no S=S in any contributors?
however, some other google images show its possible for S=S (in resonance contributor) ?
my teacher say
consider S2O32- + H+ -> S + SO32- --(1)
more difficult to break double bond, require more energy
experiment shows S forms relatively easy in (1) when S2O32- is reacted with acid (rxn 1 proceeds relatively easy)
hence should be S-S
help reconcile this ultima
-
tried to find out the reaction between S2O32- and H+, not much on the internet except this
NaS2O3 (aq) + 2HCl (aq) <----> 2 NaCl (aq) + SO2 (g) + S (s) + H2O (l)
https://www.quora.com/Why-does-sodium-thiosulphate-react-with-hydrochloric-acid
-
Originally posted by Flying grenade:
my question : why is the bond between two sulfur atoms in S2O32- a single bond? isn't forming a double bond more thermodynamically favourable?
interestingly, the Resonance Hybrid in the wiki page shows S-S !!! why?? (i.e. no partial double bond between S atoms in the hybrid so no S=S in any contributors?
however, some other google images show its possible for S=S (in resonance contributor) ?
my teacher say
consider S2O32- + H+ -> S + SO32- --(1)
more difficult to break double bond, require more energy
experiment shows S forms relatively easy in (1) when S2O32- is reacted with acid (rxn 1 proceeds relatively easy)
hence should be S-S
help reconcile this ultima
No, it is more thermodynamically feasible for S to form single bonds. You asked this question before on the forum, and I already replied you on the forum with the answer. Don't waste my time. You keep forgetting stuff I already taught you, how to get A grade for A levels???S=S is a minor resonance contributor, S-S is a major resonance contribubtor (Cambridge can ask why). For the resonance hybrid, partial double bond character must be shown, or Cambridge will penalize you.
If you can't figure out why, go ask your school teacher or private tutor. Move on.
-
Originally posted by Flying grenade:
tried to find out the reaction between S2O32- and H+, not much on the internet except this
NaS2O3 (aq) + 2HCl (aq) <----> 2 NaCl (aq) + SO2 (g) + S (s) + H2O (l)
https://www.quora.com/Why-does-sodium-thiosulphate-react-with-hydrochloric-acid
Obviously because the disproportionation of S2O3 2- under acidic conditions is thermodynamically feasible, you coconaden. -
omg thank you so much, and thank google and wiki.
i learn new important chem concepts today
Thanks Ultima
https://en.m.wikipedia.org/wiki/Double_bond_rule
http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch10/group6.php
http://www.chemicalforums.com/index.php?topic=72107.0
-
propadiene
https://en.m.wikipedia.org/wiki/Propadiene
https://www.dropbox.com/s/rr1pgyyed7lt9k2/Screenshot_2016-10-02-16-23-31-1.png?dl=0
chankimseng understanding org chem page 25
he writes : explain why CH2=C=CH2 is not a flat molecule(does he mean that propadiene is not planar??) ,
and the molecule on page26 is not planar
how to explain?
sp2 C, sp C , sp2 C are planar ain't it?
-
Originally posted by Flying grenade:
propadiene
https://en.m.wikipedia.org/wiki/Propadiene
https://www.dropbox.com/s/rr1pgyyed7lt9k2/Screenshot_2016-10-02-16-23-31-1.png?dl=0
chankimseng understanding org chem page 25
he writes : explain why CH2=C=CH2 is not a flat molecule(does he mean that propadiene is not planar??) ,
and the molecule on page26 is not planar
how to explain?
sp2 C, sp C , sp2 C are planar ain't it?
Updated : July 2017 Special Offer for JC2 Students who are interested in H2 Chemistry tuition (both 1:1 Individual and Small Group options now available).
-
thanks god
-
chan kim seng book
https://www.dropbox.com/s/wozo7xi9hlqcz6l/20161003_103104-1.jpg?dl=0
whats the diff between break and overcome
Why cannot use break?
is it cannot use 'break' becos IMF will always be present?
what are we doing when we are melting or boiling a substance? overcoming IMF of attractions/interactions?
-
Originally posted by Flying grenade:
chan kim seng book
https://www.dropbox.com/s/wozo7xi9hlqcz6l/20161003_103104-1.jpg?dl=0
whats the diff between break and overcome
Why cannot use break?
is it cannot use 'break' becos IMF will always be present?
what are we doing when we are melting or boiling a substance? overcoming IMF of attractions/interactions?
Stop reading notes / books and spamming your own conceptual qns, and starting practicing 2016 Prelim papers and asking questions from there.Yes, yes.
-
NH3 condenses at -33°c (it's boiling point)
boiling point H2 = -253°c
boiling point N2 = -196°c
-
why NH3 forms liquid from the gaseous state most easily?
Hbonding allows molecules to come together , so less energy needed to condense it?
-
Mr of H2 = 2 gmol-1
-
i thought stronger IMF yields higher BP, not lower BP?
update : yes statement is correct
-
update :
stronger IMF higher BP, weaker IMF lower BP
for stronger IMF, less energy required to condense the gaseous molecules to its liquid
weaker IMF requires more energy to condense it's gaseous molecules to it's liquid
-
cool the environmental temperature such that the KE of molecules is reduced and hence do not have sufficient KE to overcome the intermolecular forces of attractions and hence IMF becomes significant and hence the liquid is formed
-
Be careful. You keep indulgently OCD thinking about conceptual ideas over and over again, it may give you the self-consolation that you understand your Chemistry better than your peers, but in the end you'll still lose out to your peers (in terms of A level grade) who spend the time practicing lots of Prelim papers instead of self-indulgently fantasizing and nitpicking about concepts.
I don't blame you for having the obsessive-compulsion to want to fully sort out your conceptual ideas, but this is physical incarnation and you gotta strike a balance with practicality. It's no use understanding your concepts better than your peers, yet still score a worse final grade than them due to lack of practice of exam papers under exam conditions.
-
ooh H2SO3 is a weak acid ?
H2SO4 is a strong acid right
-
conjugate base of H2SO3 isn't stable?
-
so2(g) forms an equilibrium in water with so2(aq)