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last SG · 2015-08-19T22:54:00+00:00

Topic : atomic radius Hi! This is from singapore cambridge nov a level exam year 2010,Paper 1 qn 1Qn: which element has the largest atomic radius?BrKKrScSo...

Flying grenade SG

I cant find any questions with the title ’ by product’ or ‘side product’ in the list on your website

Flying grenade SG

Whats the diff between phase and states of matter?

E.g gaseous phase / gaseous state

Flying grenade SG

http://infinity.usanethosting.com/Tuition/H2Che…

Sir for part 2 is the answer 0.229 kg (3sf)?

UltimaOnline SG

I typed the title using "byproduct" and "sideproduct". Look for it manually 1-by-1 lah, then you can see what other fun goody questions I have.

For A level H2 Chem syllabus purposes, no diff.

Flying grenade SG

Do we need to know anything abt kstab?

Flying grenade SG

Walao sian wrong! !!!!!!!!!!
Sir can help checkkkk )):

Qn : For how much ice (kg) is it required to cool the water from 20 to 5°celSius ?

Q1 = heat transferred to change temp of ice from -15 to 0°C (Endo)
Q2 = heat transferred to change solid ice to liquid water at 0°c (endo)
Q3 = heat transferred to change temp of water from 0 – 5°C (endo)
Q4 = heat transferred to change liquid aqueous drink from 20-5°C (exo)

at thermal eqm Q1+Q2+Q3+Q4 = 0

Flying grenade SG

Yea i looked 1 by 1
Hehe found it alr after 2nd try! !!

Ur website so awesome!!!!!
Ucdavis website credible hor?

UltimaOnline SG

Walao sian wrong! !!!!!!!!!!
Sir can help checkkkk )):

Qn : For how much ice (kg) is it required to cool the water from 20 to 5°celSius ?

at thermal eqm Q1+Q2+Q3+Q4 = 0

Ooops pai sei, my bad. Your answer is correct, I didn't read properly. Well done Lol!

UltimaOnline SG

Yea i looked 1 by 1
Hehe found it alr after 2nd try! !!

Ur website so awesome!!!!!
Ucdavis website credible hor?

Yeah, but of course, in my question using their image (with acknowledgements), we're talking literally hydrolysis (ie. using water as a reagent). In the H2 syllabus, becoz time is money, to save time we use a stronger nucleophile and base, NaOH(aq) and NaOH(ethanol), and thus the by-product will be be NaBr instead of HBr. But you get the idea.

UltimaOnline SG

Do we need to know anything abt kstab?

Good to know (afterall, it combines equilibria and complex ions in the H2 syllabus), Prelim papers often ask on it, and Cambridge can use it in a data-based qn (ie. they tell u what's Kstab, then ask u to apply).

Flying grenade SG

Rj book ionic equilibria page 285

Exercise: analysing a mixture of NaHCO3 and NaOH

Is the conc NaOH given by the answer 0.430mol/dm3 correct?

I tried both different method twice,

I got [NaOH] 0.130mol/dm3

Also, actually, i dont really understand the examples.

Why vol of hcl required to react with NaOH intially present in the mixture, can be equated to Vhcl used during first end point minus Vhcl used in 2nd end pt??

So like 1st end pt only have oh-??then after all oh- are neutralised, then suddenly have HCO3- ion come out from the dissociation of NaHCO3??

Shouldn't the dissociation be concurrent?

Is it becos strong base suppress the dissociation of WB NAHCO3?

If ^ that is the case, then why the book indicated 'at the first end pt, total amount of hcl reacted with both Na2CO3 and NaOH = the vol hcl used in first end pt??? Im confused and i dun uds dun get it ...

Can help improve my phrasing or how should i ask my question in the proper manner also

Flying grenade SG

And i have no idea why when i post posts in this forum, sometimes some portions of the words become small or big..
Sorry for the weird word warping above^
I have no idea of how rectify or fix it

Flying grenade SG

Zzzzzzzzzzzzzzzzzzzz. They gave explanation on the following page 287. Zzzzzzzz
I wasted alot of time contemplating and thinking about it. =_=

You could still kindly input anything if you would like
I appreciate and thank you so much ultima (:

UltimaOnline SG

25 cm3 of NaHCO3 and NaOH titrated against 0.5M HCl. 21.5cm3 and 15cm3 of HCl required to reach 1st and 2nd equivalence points respectively. Find the molarities of NaHCO3 and NaOH.

Solution :

Molarity of NaOH = moles of HCl which neutralized NaOH / 25cm3 volume = (0.5(21.5/1000)) / (25/1000) = 4.3x10^-1 M

Molarity of NaHCO3 = moles of HCl which neutralized NaHCO3 / 25cm3 volume = (0.5(15/1000)) / (25/1000) = 3x10^-1 M

Flying grenade SG

Whats the difference between L (levo) and D (dextro) , And sinister and dexter isomers???? And also R and S isomers??

UltimaOnline SG

Whats the difference between L (levo) and D (dextro) , And sinister and dexter isomers???? And also R and S isomers??

To answer your question, read :
https://en.wikipedia.org/wiki/Chirality_(chemistry)#Naming_conventions

For H2 Chemistry, if asked to name the enantiomers, Cambridge will accept either (+)/(-) or d/l labelling based on optical activity, or the R/S labelling based on the Cahn–Ingold–Prelog priority rules (which are also used for E/Z labelling system for alkenes, which is more versatile than the limited cis/trans system, and is also accepted by Cambridge for H2 Chemistry) though the R/S and E/Z labels are not compulsory for H2 Chemistry as it's not within syllabus, and only required for H3 Chemistry. The D/L labelling is used in biochemistry (H2/H3 Biology).

Flying grenade SG

There’s
Cis trans
(+)/(-)
d/l
D/L
Rectus sinister
E Z rules

Which one is for geometric isomerism and optical isomerism?

Which one rotates clocks and anti clockwise?

Only manage to find for R and S , which is clockwise for rectus and anticlockwise for sinister

UltimaOnline SG

There’s
Cis trans
(+)/(-)
d/l
D/L
Rectus sinister
E Z rules

Which one is for geometric isomerism and optical isomerism?

Which one rotates clocks and anti clockwise?

Only manage to find for R and S , which is clockwise for rectus and anticlockwise for sinister

No seriously, all the info is out there. Not gonna spoonfeed you anymore here (besides, most of this is optional stuff, beyond the H2 syllabus essentials). Go read 5 diff websites (including Jim Clark's, Khan's Academy, etc).

Flying grenade SG

2010 p3 qn 1d
Sir ultima can help check my drawings

For cpd A, the cl is substituted at that position is it because it is most stable there because attached to 3 mildly electron donating C group ah? Markovnikov’s rule ah?

For D, im asking this as an extension
When the Br is being eliminated, are there 2 other by-product as drawn?

https://www.dropbox.com/s/lo7wynbasjbmo7k/20151…

Flying grenade SG

Wait for ^ should *side* product be the proper term to use? Haha

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