Originally posted by Flying grenade:ooh H2SO3 is a weak acid ?
H2SO4 is a strong acid right
H2SO4 is a diprotic acid. The 1st proton dissociation is complete hence is technically strong (ie. stronger than hydroxonium ion). the 2nd proton dissociation occurs incompletely in aqueous solution, yet to a significant extent, hence HSO4- is technically weak (ie. weaker than hydroxonium ion) but is still considerably acidic (HSO4- is actually even more acidic than Al3+).
H2SO3 is a diprotic acid. The 1st proton dissociation occurs incompletely in aqueous solution, yet to a significant extent, hence H2SO3 is technically weak (ie. weaker than hydroxonium ion) but is still considerably acidic (H2SO3 is actually even more acidic than Al3+). The 2nd proton dissociation is rather weak (ie. significantly weaker than hydroxonium ion), and simultaneously considering both the acidic and basic hydrolysis of the amphiprotic HSO3- ion, the pH of a solution containing only the HSO3- ion would be only approximately 4.5 (ie. HSO3- is actually even weaker an acid compared to Al3+).
https://www.dropbox.com/s/obib20r7ffbrr8n/20161003_225535-1.jpg?dl=0
i can only think if low temp due to cold water may not provide the necessary energy needed to overcome Ea barrier
how does the hydrolysis of SiCl4 being exothermic affects the extent of rxn? what's the link?
Originally posted by Flying grenade:https://www.dropbox.com/s/obib20r7ffbrr8n/20161003_225535-1.jpg?dl=0
i can only think if low temp due to cold water may not provide the necessary energy needed to overcome Ea battier
how does the hydrolysis of SiCl4 being exothermic affects the rxn? what's the link?
http://sgforums.com/forums/2297/topics/441379?page=2
Temperature is actually more important than limited/excess water. (Just as temperature is the more important factor when determining oxidation of alkenes to diols versus oxidative cleavage, over other factors such as pH and concentration).
dk the link between exo and temp . no equilibria involved also
tried very hard to google but yielded no pertinent/relevant findings
moved on alr, in the meantime,
anyone please feel free to answer my qn
why using cold water, results in partial/limited hydrolysis of PCl5 and SiCl4
additional, not so important qn : is there any link to exothermic rxn? if so, what's the link?
temp affects kinetics
partial hydrolysis of SiCl4 is an exothermic rxn
Originally posted by Flying grenade:tried very hard to google but yielded no pertinent/relevant findings
moved on alr, in the meantime,
anyone please feel free to answer my qn
why using cold water, results in partial/limited hydrolysis of PCl5 and SiCl4
additional, not so important qn : is there any link to exothermic rxn? if so, what's the link?
temp affects kinetics
partial hydrolysis of SiCl4 is an exothermic rxn
For reactions that can proceed at rtp, in limited water, write the partial hydrolysis equation ; in excess water, write the full hydrolysis equation. If not sure if water is limiting or excess, be BedokFunland JC exam-smart and write both (with qualification and/or explanation).
That's it liao, stop OCDing over this. I won't reply anymore on this. Go ask your school teacher or private tutor. Go waste their time, don't waste mine.
Originally posted by Flying grenade:enantiomers
- Same physical properties except that they rotate plane polarised light in opposite directions
- Same chemical properties except when another chiral molecule is involved. <-- what does this mean?
OHHH OKAY THANK U SO MUCH ! alot of ur replies we dunno and didnt even thought about it
thanks for teaching us
lol (non) innocent ligand
https://en.m.wikipedia.org/wiki/Non-innocent_ligand
One of the reactants, A, for example, would have a significantly high concentration, while the other reactant, B, would have a significantly low concentration
One way to create a pseudo-1st-order reaction is to manipulate the physical amounts of the reactants. For example, if one were to dump a liter of 5 M HCl into a 55 M ocean, the concentration of the mixture would be closer or equal to that of the ocean because there is so much water physically compared to the HCl and also because 55 M is relatively larger compared to 5 M.
this is for http://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Kinetics/Reaction_Rates/Second-Order_Reactions/Pseudo-1st-order_reactions
the rate is apparently independent of the reactant concentration. The rates of these zero-order reactions do not vary with increasing nor decreasing reactants concentrations. This means that the rate of the reaction is equal to the rate constant, k, of that reaction. This property differs from both first-order reactions and second-order reactions.
http://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Kinetics/Reaction_Rates/Zero-Order_Reactions
IJC 2016 P2
https://www.dropbox.com/s/kcwxb76pfu81oq2/20161004_194848.jpg?dl=0
from above, for zero order of rxn , the rate is apparently independent of the reactant concentration.
idk when use pseudo zero order or pseudo first order
ok for more common one, for water, is the order of rxn wrt H2O pseudo first or zero?
what abt other cases like the IJC one above, where the answer gave the order of rxn to be pseudo first
it's really confusing , for pseudo zero and pseudo first
is it for pseudo first, the rate of reaction is still dependent on the reactant, albeit independent of concentration or partial pressure of the reactant
pseudo zero is independent of the reactant
then for water, sometimes pseudo first sometimes pseudo zero , quite confusing
is it like for most cases,
when H2O is in large excess/concentration remains relatively same, order of rxn wrt [H2O] is pseudo zero
when an reactant is in large excess/concentration remains relatively same, order of rxn wrt [reactant] is pseudo first
Consider the hydrolysis of ester. The reaction is actually 1st order wrt to H2O, and 1st order wrt to ester, hence overall order of reaction is 2nd order. If you have H2O in large excess, then H2O becomes pseudo-zero order, then overall order of reaction becomes pseudo 1st order. In which case you can use constant half-life (applicable only to overall 1st order or overall pseudo 1st order reactions) of ester to determine the value of k' (ie. ln2 / half-life), then from k' = k [H2O], you can obtain the value of k.
To see how to apply what I just said to an actual A level exam question, see my BedokFunland JC question (on my BedokFunland JC website) : Kinetics_calculate_rate_constant_k
If using PC, you can control-F to search for keywords such as "Kinetics_calculate_rate_constant_k"
PS. Why don't I just provide a direct link? Coz I want to encourage you guys to be familiar with navigating to my list of other BedokFunland JC H2 Chem questions on my website.
All my teachers in my school taught Everyone Cl2 should be pseudo first order for that IJC qn.
their wrong right? (oxymoron)
Originally posted by Flying grenade:All my teachers in my school taught Everyone Cl2 should be pseudo first order for that IJC qn.
their wrong right? (oxymoron)
Originally posted by UltimaOnline:For the IJC qn, to determine the order of reaction wrt NO2, you need to make Cl2 pseudo zero order, by having it in large excess. Then the data shows that the rate of reaction is directly proportional to (partial pressure of NO2)^2, hence rate of reaction is second order wrt NO2.
Consider the hydrolysis of ester. The reaction is actually 1st order wrt to H2O, and 1st order wrt to ester, hence overall order of reaction is 2nd order. If you have H2O in large excess, then H2O becomes pseudo-zero order, then overall order of reaction becomes pseudo 1st order. In which case you can use constant half-life (applicable only to overall 1st order or overall pseudo 1st order reactions) of ester to determine the value of k' (ie. ln2 / half-life), then from k' = k [H2O], you can obtain the value of k.
To see how to apply what I just said to an actual A level exam question, see my BedokFunland JC question (on my BedokFunland JC website) : Kinetics_calculate_rate_constant_k
If using PC, you can control-F to search for keywords such as "Kinetics_calculate_rate_constant_k"
PS. Why don't I just provide a direct link? Coz I want to encourage you guys to be familiar with navigating to my list of other BedokFunland JC H2 Chem questions on my website.
ok thanks for this reply. understood
Originally posted by UltimaOnline:
Yeah, but the answer you copied down (ie. your corrections) from your teacher is fine.
ok noted thanks.
but yeah they said its pseudo first order (which i didnt copy) which is wrong
i feel damn ._.
then we rarely encounter pseudo first?
overall pseudo first is fine
Originally posted by Flying grenade:then we rarely encounter pseudo first?
overall pseudo first is fine
whats the implication/meaning of pseudo first?
is it for pseudo first, the rate of reaction is still dependent on the reactant, albeit independent of concentration or partial pressure of the reactant
how to make pseudo first? may it high in concentration such that it's in large excess too?
Originally posted by UltimaOnline:
Only for overall.
okay