And for many of you who just completed your 'O' levels, you can look forward to learning (in your JC or Polytechnic course) why some ionic compounds are insoluble in water (and hence precipitate out as a solid) while others are soluble in water.

 

 

Originally posted by SMT: Persona:

Hi guys! I'm new to this forum and I have some unanswered question about studying abroad and scholarships and I believe the answers can be found by fellow Singaporeans here.. Okay I would like to study abroad in Japan... But I don't know about scholarships, how to obtain and apply for it, what the requirements are, and will I have to go through NS first? If I have to go through NS then I probably might only go to Japan to work there but that'll be later... I don't know why but I like Japan for some reason.. So yeah I need advising...

 

>>> I don't know why but I like Japan for some reason <<<

 

Well, this american dude (video below) knows why *he* likes Japan :

http://www.youtube.com/watch?v=51QXhWGoMHE

Originally posted by prg:

 

Can anybody give a list of schools in Singapore that offers CIE -A level?? Please provide appropriate websites if possible. 

 

I have heard that the papers for Science and mathematics subjects are different in singapore from the ones world wide, something called Integrated Programme Singapore-Cambridge GCE. Is this true ? 

If it is true, how different is it? Is it possible to take only the papers that are same worldwide, instead of the singpore ones?? 

 

I have already taken physics, chemistry and maths subjects, outside singapore (AS level exam) which have for eg. chemistry subject code: 9701. this subject seems to have a different subj. code in singapore. Is it possible to take just the Cambridge GCE 'A' Level instead of the Integrated Programme in Singapore??

Please do provide extra  information, as I'm not knowledgable about this!!

 

SEAB (Singapore Examinations and Assessment Board) is phasing out the 'A' level syllabus (the international CIE syllabus) in favour of the Higher (H2/H3/H1) syllabuses.

 

Strangely enough, according to the SEAB website below, from 2009 onwards (inclusive), private candidates are only allowed to take the new H2 syllabuses, but school candidates (the 'repeat students') are still allowed to take the old 'A' level syllabuses syllabus (the international CIE syllabus).

 

Singapore Examinations and Assessment Board

http://www.seab.gov.sg/

 

You may try to contact the schools on this list to see if you can register with them to take the old 'A' level syllabus (the international CIE syllabus) :

http://www.singaporeexpats.com/guides-for-expats/international-schools.htm

 

 

If you wish to consider taking the Singapore H2 syllabus exams (it should be regarded as equivalent to the old 'A' level syllabus, and it is still certified by Cambridge University), but would like to inquire further on this matter, contact SEAB.

 

Originally posted by bonkysleuth:

I was going through my textbook and found some experimental steps which I do not understand why they should be performed.

 

1. Before reacting some metal strips, you are required to clean it with sandpaper. Why is that so?

 

2. What is the salt given off when H2SO4 reacts with NH3?

 

3. In identifying Anions, what is the purpose of adding silver nitrate after adding HNO3? (eg. to test for Cl-)

 

4. What are the uses of the products of the Haber process? The product here refers to NH3, does it?

 

Do respond to my queries if you can. Many Many thanks!

Good attempt at helping bonkysleuth, starmoonsun. Though you didn't directly answer his questions, but your comments are fairly correct, if incomplete.

 

 

Q1) starmoonsun has given the reason, though he/she didn't explicitly identify the compound, which is the metal oxide (which may or may not be insoluble and corrosion resistant, depending on the metal. Regardless, sandpapering would do the job of removing the oxide layer).

 

Q2) (Proton transfer) x 2  from the diprotic acid to the base; conjugate base is the deprotonated sulfuric acid aka sulfate(VI) anion, conjugate acid is the protonated ammonia aka ammonium cation; hence salt formed = (NH4)2SO4(aq).

 

Q3) If a white ppt is observed, the white ppt must be AgCl(s) and hence Cl- ion must have been present. A higher order question here would be, "Give two possible reasons why nitric acid must be added, before adding AgNO3(aq)". For the answer, control-F (ie. "find") "silver nitrate" here :

http://www.sgforums.com/forums/2297/topics/320107

 

Q4) See

http://www.google.com.sg/search?hl=en&q=uses+of+ammonia&meta=

This is an important thread (over 10 pages and 200+ posts long) with many thoughtful posts (and often with multiple opposing viewpoints), regarding the Singapore Education System, that everyone, especially secondary school 'O' level students, would be well advised to read.

 

More top O-Level scorers choosing polytechnic route

 

 

There really is no easy solution, no right nor wrong. MOE themselves, are constantly struggling to balance students' wants with the needs of society. (Sure they could just have popular courses like medicine, law, banking, and make them available to every student who wants it; then the entire country would be overrun by only doctors, lawyers and bankers, and no one else left to do everything else that needs to be done and society would collapse.)

 

If you think you have some brilliant suggestions (on this issue) for MOE to take into consideration in planning the future of the Singapore Education System, do your part as a Singaporean and share your thoughts (on the original thread, on this thread, on the Straits Times Forum, email to MOE, etc).

 

 

Originally posted by SBS7484P:

sodium phosphate - what state is it in at r.t.p?

That's up to you to decide. Is it hydrated or anhydrous?

 

>>> h1 student: Teacher, why is it that ?

trollteacher: This is in H2 syllabus. You dont need to know.

h1 student: But teacher, i want to gain more knowledge.

trollteacher: You cant even do well in simple h1 syllabus. Wake up your idea and stop asking so many irrelevant questions.

h1 student drops out. <<<

That's a very accurate picture of what happens in every JC. Which is why a supportive tutor who is willing to encourage the student to truly understand and appreciate the science for what it really is (regardless of silly syllabus limitations) can be tremendously helpful to the student's enjoyment.

 

Of course, not everyone has the time or money or opportunity for tuition. But how it goes on in schools, both secondary schools and JCs, doesn't look like it's going to ever be changing for several reasons :

 

1) MOE teachers are severely overworked (but again, 'tong ren bu tong ming', just like in the SAF, for instance, some pple slack, some pple kena crap-work all the way. So *many*, not all, MOE teachers are severely overworked. Others just backstab to take credit, for instance). So they won't have the time or energy to give every student full support, like a private tutor can.

 

2) The syllabus, curriculum and system, is superficially results oriented, rather than true results oriented. True results, includes the student truly understanding and enjoying the process, so that he/she may have the motivation to contribute to humanity with his/her own unique insights, research and exploration. But being superficially results oriented, the JC teachers feel their priority is just to get students to blindly memorize to get marks. A good tutor, has the time and opportunity to help students to understand and enjoy at the same time as also memorizing to get full marks. 

 

3) There are many teachers out there (both Sec sch and JCs), who do not themselves have a healthy mindset or attitude towards teaching and the students' learning. Every teacher, like every human being on this planet, is unique. I've met many colleague teachers whom I disagree on their teaching (content, method, style, etc). And students from other classes have said they wished I was their teacher instead. (this isn't so much about ego or advertising, it's to make a point - there are all kinds of teachers (just as they're all kinds of doctors, psychologists, philosophers, religious pple, etc), it's errorneous to overgeneralize to say most MOE teachers are horrible, or most MOE teachers are wonderful. They are individuals, with all individual kinds possible.) 

 

 

 

 

>>> i think it is quite weird to focus so much on molecular biology, instead of the general biology (as in the former A level biology syllabus)

>>> All of this is thanks to the farsightedness of the Singapore Government, who has decided that being extra kiasu in training our students, will give Singapore a competitive edge over other countries. <<<

 

I wasn't being sarcastic, btw, coz I actually agree with the Sg Govt on this one (as far as the H2/H3 sciences are concerned; but not necessarily on other education policies or curriculums. I think PW is problematic, for instance.)

 

 

Did you know...

 

The H2/H3/H1 system and syllabuses, is unique in the world, only Singapore has it. No other country in the world (including USA and UK) takes the H2/H3/H1 syllabus, they all have a more standardized 'A' level syllabus, even across examination boards (ie. the 'A' level syllabus for Cambridge, Oxford, AQA, EdExcel (the 1st 2 are UK, the last 2 are USA) are almost all the same, and quite significantly different from the H2/H3/H1 syllabus that Singapore candidates experience.

 

All of this is thanks to the farsightedness of the Singapore Government, who has decided that being extra kiasu in training our students, will give Singapore a competitive edge over other countries.

 

Subjects wise, the H2 syllabus differs most significantly from the rest-of-the-world 'A' level syllabus, for Biology (and to a lesser extent, for Chemistry and Physics).

 

'O' Level Chem.

 

anpanman posted :

>>> We encounter questions regarding the reduction of metal oxides by a reducing agent, such as carbon. The "standard" equation goes something like this

 

Metal oxide + carbon ---(heat)---> metal + carbon dioxide

 

However, i discovered that there were some reactions such as reduction of zinc oxide and lead(II) oxide which produce CO instead of CO2. I would appreciate if someone could explain. Thanks. <<<

 

 

I replied :

Zinc is a relatively (everything's relative... just ask Einstein) reactive metal, which means that it won't be that easy to grab away zinc's girlfriend ("oxygen"). Carbon can grab away oxygen from zinc, but it's harder for carbon monoxide to do so.

 

Carbon : "Eh gimmie ur oxygen gf, or else I call my gang whack u!"

Zinc Oxide : "Ok ok, I give u face this time... but I'll remember ur face... u be careful..."

Carbon (now in monoxide form, ie. Carbon monoxide) to Zinc (who has lost his oxygen) : "Muhahaha! Ok, now ur brudder's turn... tell your younger didi zinc oxide to give up his oxygen too!" 

Zinc & his brudder Zinc Oxide : "Oi! U already got one oxygen liao, don't be too greedy hor! Don't see we all quiet quiet good to bully, think we sick kitten izzit! Knn u nvr die b4 izzit, I tell you..."

Carbon monoxide : "Ok lah! ok lah! Kao peh lah!"

 

Originally posted by weewee:

First of all, you might have gotten me mixed up with wee_ws who is another forumer.

Secondly, it was never my intent to impersonate Strategic Tuition but i might have been brainwashed into using that nick when i see so many of eagle's posts. I apologise if it has caused any harm or defamation and i will not use that nick again.

Thirdly, i have a full time job which is not a teacher but i love to teach so i am taking up tuition part time. I also plan to be self sufficient from tuition alone.

I have learnt a great deal about tuition from here. Eg. No spoonfeeding, encourage thinking students, encourage asking of questions, getting foundation right, teaching the right concept, TYS at the right time. Thanks all.

Peace. May the force be with you all.

 

Hi weewee. Certainly no apologies needed! I can't speak for Eagle of course (every man can only speak for himself. No one can judge you except yourself. You are the master of your own soul, the captain of your own destiny... etc), but I'm very sure Eagle was just kidding around when he did the "" face and said, "Someone copied my idea and came up with the nick Strategic Tutor????"

 

>>> I apologise if it has caused any harm or defamation and i will not use that nick again. <<<

I'm sure it's a much better idea to continue using that nick, and when you've setup your tuition webpage, why not do a link exchange with Eagle and with myself, it's a win-win-win deal for everyone!  

 

Happy Seasons Greetings, all!

Originally posted by anpanman:

More often than not, we encounter questions regarding the decomposition of metal oxides aided by a reducing agent, such as carbon.

 

The "standard" equation goes something like this

 

Metal oxide + carbon ---(heat)---> metal + carbon dioxide

 

however, i discovered that there were some reactions such as reduction of zinc oxide and lead(II) oxide which produce CO instead of CO2.

 

I would appreciate if someone could explain. Thanks.

 

Zinc is a relatively (everything's relative... just ask Einstein) reactive metal, which means that it won't be that easy to grab away zinc's girlfriend ("oxygen"). Carbon can grab away oxygen from zinc, but it's harder for carbon monoxide to do so.

 

Carbon : "Eh gimmie ur oxygen gf, or else I call my gang whack u!"

Zinc Oxide : "Ok ok, I give u face this time... but I'll remember ur face... u be careful..."

Carbon (now in monoxide form, ie. Carbon monoxide) to Zinc (who has lost his oxygen) : "Muhahaha! Ok, now ur brudder's turn... tell your younger didi zinc oxide to give up his oxygen too!") 

Zinc & his brudder Zinc Oxide : "Oi! U already got one oxygen liao, don't be too greedy hor! Don't see we all quiet quiet good to bully, think we sick kitten izzit! Knn u nvr die b4 izzit, I tell you..."

Carbon monoxide : "Ok lah! ok lah! Kao peh lah!"

 

Originally posted by eagle:

Huh which forum?

Someone copied my idea and came up with the nick Strategic Tutor????

 

>>> Huh which forum? Someone copied my idea and came up with the nick Strategic Tutor????  <<<

 

So you can understand why I thought it was you, Eagle.
http://www.sgclub.com/singapore/anyone_participated_maths_110650.html

Originally posted by eagle:

Weewee don't teach Physics

Let's see... you're "Strategic Tutor", and you made the exact same post (albeit on a different forum) as WeeWee did about Maths Olympiad... why? (just curious)

 

 

Unless it is WeeWee who is "Strategic Tutor"? But Strategic Tuition is yours (Eagle's). So what's this about? (just curious).

 

 

 

Seriously, we all know WeeWee and Eagle are two different (both distinguished, reputable) persons of achievement. Don't get the wrong idea. No accusations whatsoever here. It's just that it's humourous to notice two exact same posts made (on maths olympiad). So I'm just curious. Don't angry hor (WeeWee and Eagle).

Originally posted by weewee:

What kind of training did you undergo before you took part?

Here are some results.

http://www.hci.sg/aphelion/apmops/SMOPS%20Local%20Results%2008%20(Webpage)(30%20April).xls

http://sms.math.nus.edu.sg/Competitions/SMO2008.aspx

So weewee = Eagle = StrategicTutor. Secret identity crisis revealed! 

http://www.sgclub.com/singapore/anyone_participated_maths_110650.html

 

Just kidding guys, I know WeeWee isn't Eagle... or is he?

EdExcel official website

http://www.edexcel.com

 

Cambridge International Examinations official website

http://www.cie.org.uk

Everything you wrote (assuming you recalled the question's specifications accurately) seems to be in order. You should get all your marks. 

 

 

Ok, I've checked it out, with multiple high-level reliable sources. I know you guys are gonna hate the findings I'm about to reveal. (I actually love it. But then, because SEAB-Cambridge might not be as open-minded as to see the bigger picture, meaning in effect you guys might still lose your marks even though your answer is arguably correct, so I can understand and sympathize, that you might not find this quite as fascinating as it really should be. Lastly, there's the matter of the ratio of ions involved. If this is specified in the actual question, that those are clues (that you ought to have taken into consideration) leading to only 1 acceptable answer per question part, in which case you can't say SEAB-Cambridge wasn't fair to you).

 

[CuCl2]- or dichlorocopper(I) anion exists, and is linear geometry.

 

But [CuCl4]3- or tetrachlorocopper(I) ion exists too, and can exist in either tetrahedral geometry, or octahedral & square planar geometry if it's [Cu(Cl4)(H2O)]3-. 6 ligands form an octahedral geometry, the Cl- ligands occupy square planar while the H2O ligands occupy top and bottom.

 

[CuCl4]2- or tetrachlorocopper(II) ion exists too, and can exist in either tetrahedral geometry, or octahedral & square planar geometry if it's [Cu(Cl4)(H2O)2]2-). 6 ligands form an octahedral geometry, the Cl- ligands occupy square planar while the H2O ligands occupy top and bottom.

 

Since all 5 of the above ions exist, arguably SEAB-Cambridge should accept more than one possible answer for at least some of the questions. But whether they do, is another matter altogether. Also, I didn't actually read the exact phrasing of the question itself, and if the SEAB-Cambridge question specified the ratio of Cl- ions to the metal cation in each case, then there may only be 1 acceptable answer for each question part, and you can't say SEAB-Cambridge is being unfair to you.

 

 

A couple of points (this may go against how you're feeling now, but Chemistry is really about learning how beautiful the Universe is, not about scores/marks/points and hollow paper qualifications. So take this as a post-course continuing journey of exploration and wonder).

 

The more (dative aka coordinate) bonds a central metal ion can form with ligands (electron donors), the happier it will be. Simply because more bonds formed results in a more exothermic process, which as far as Gibbs Free Energy is concerned, is certainly a good, feasible thing. True, there might be a slight decrease in entropy as a result (which is not a good, feasible thing), but usually the favourable enthalpy change outweighs the unfavourable entropy change. There is also electronic stability to consider, of course.

 

You should be aware that Be2+ ion, being in period 2, does not have empty 3d orbitals required to expand its octet. Consequently, any complex ions formed with Be2+ has to be tetravalent or 4 bonds, ie. tetrahedral geometry.

 

In that case, why would Cu+ or Cu2+ want to just form CuCl or CuCl2 and stop there? Wll there's obviously the matter of molarity and availability to consider. If there's enough Cl- ions available, it makes sense that you would want to get [CuCl2]- ion and (adding even even more Cl- ions) [CuCl4]3- ion, and for Cu2+ ion, you would obtain [CuCl4]2- ion.

 

But if the more bonds formed the merrier, then why stop at 4 Cl- ion ligands? Why not 6 Cl- ligands? Because Cl being in period 3, is too huge to have 6 Cl- ligands crowding around the central metal ion. There would be too much electronic and steric repulsion.

 

So we only get 4 Cl- ligands? Then obviously, we would get a tetrahedral geometry, wouldn't we? (Notice the JC notes chillax posted above, like all JCs' notes, are inadequate in that they just expect students to memorize without understanding, without proper explanation. Typical JC stuff.)

 

But compare the H2O molecule to Cl- anion. H2O is much smaller (for 2 reasons - Cl- is in period 3 and it is an anion too). Hence, the [Cu(H2O)6]2+ and [Cu(H2O)6]+ ions exist (though the process is not as exothermic as if Cl- ligands were used, hence ligand displacement or ligand exchange takes place).

 

Which means that even in tetrachlorocopper(I) and tetrachlorocopper(II) ions, it is possible, under different conditions, that water molecules might squeeze in between the Cl- ligands, and you would get the octahedral geometry. 6 ligands form an octahedral geometry, the Cl- ligands occupy square planar while the H2O ligands occupy top and bottom. (notice that the JC notes don't explain this? tsk tsk.)

 

The reason why Cl- ligands occupy square planar, is because they're much larger, bring greater electronic and steric repulsion as compared to the smaller H2O ligands, and hence square planar for the 4 Cl- ligands would be furthest apart and the most stable, while the smaller H2O ligands occupy top and bottom.

 

That being said, the tetrahedral [Cu(Cl)4]2- and [Cu(Cl)4]3- complex ions also exist, just as the 'square planar' (octahedral, really) [Cu(Cl4)(H2O)2]2-) and [Cu(Cl4)(H2O)2]3-) complex ions also exist.

 

 

 

Delightful, ain't it?

 

 

 We Love Chemistry

Originally posted by arigatoast:

ans is 1) C2H7N

ratio of X : CO2: N2

            2       4       1

that means there are 4/2=2 carbon atoms  in X

which also means there is 2/1= 1  N atom in X

 

Ah, I see arigatoast hit the "post" button before me. He's quick on the draw. Fast and reliable service, with a "" (smile) too.

 

 

 

Originally posted by Bigcable22:

found this puzzling question in my friends worksheet..  not in CxHy ..

In an experiment 10cm^3 of organic compound X in the gaseous state was sparked in excess oxygen.20cm^3 of carbon dioxide and 5cm^3 of nitrogen were obtained among the products.All gas volumes were measured at the same temperature and pressure.

which of the following compounds could be X?

1.) C2H7N

2.)C2H6N2

3.)C6H5NO2

4.)C3H5N

 

This question is in error. In every one of the 4 options, combustion in excess oxygen would definitely produce several species of oxides of nitrogen (NxOy), and not nitrogen gas.

If ignoring this critical error AND assuming the only product of combustion containing nitrogen is N2 gas, then the answer would be option 1, since by stoichiometry, combustion of 10cm3 of the compound produces 20cm3 CO2 implies 2 C present, and 5cm3 N2 produced implies 1 N present. The hydrogens in the compound would simply be oxidized to water. 

'A' Level Qn.

 

Someone posted :
>>> What is the major organic product of the reaction of 2,3-Dimethyl-1,3-butadiene with Br2? <<<

 

 

Solution / Comments :

For the mechanism, the first step is nucleophilic attack resulting in electrophilic addition (where the pi bond acts as the nucleophile); the second step is nucleophilic attack resulting in nucleophilic addition (where the Br- (or OH- if aqueous conditions are used) acts as the nucleophilie).

 

Four points to consider :

 

1) The solvent used matters. With a non-polar, inert solvent, you'll get the addition of bromine only. Using aqueous bromine, you have a competing hydroxide ion nucleophile that will attack the cyclic bromonium carbocation intermediate, in effect adding not just Br, but also OH, across the double bonds.

 

2) If we regard the cyclic bromonium ion as a non-cyclic carbocation, (eg. imagine you're adding H-Br instead of Br-Br), then the more stable carbocation would be the one with more electron donating (non-electronegative-substituted) alkyl groups. If both double bonds are added across simultaneously, and based on this argument alone, you would end up with 1,4-dibromo-2,3-dihydroxy-2,3-dimethyl-butane.
 
3) However, because oxygen is significantly more electronegative than bromine, the resulting electronic instability of 1,4-dibromo-2,3-dihydroxy-2,3-dimethyl-butane (with the two partial +ve Cs being adjacent), may see the emergence of 2 other slightly more stable isomers (at least in regard to the two partial +ve adjacent Cs), 1,3-dibromo-2,4-dihydroxy-2,3-dimethyl-butane and 2,3-dibromo-1,4-dihydroxy-2,3-dimethyl-butane.

 

4) Let's consider sterics. Br is huge, but OH is small. But Br has to be added on first, since the pi-bond acts as a nucleophile (and attacks the +ve charged Br). So the next step of OH- nucleophile attacking the carbocation (or bromonium carbocation), might preferentially add on to the terminal C's, to minimize steric repulsion (or van der Waals repulsion), so this argument tends towards the isomer 2,3-dibromo-1,4-dihydroxy-2,3-dimethyl-butane.

The answer (single major product) isn't directly provided by this post, but hopefully these 4 points above might have possibly helped you understand the processes or considerations involved a little better.

Originally posted by JY:

I'm not even done with it yet! 3 more semesters to go, haha! But what concerns us mainly would be the entire process to mass produce something useful. Can be organic or inorganic. Chemists decide the route of synthesis in test tubes. Chemical engineers upsize it to mega huge reactors.

In the final analysis of the process we have to take into consideration many factors. Thermodynamics decides process feasibility at optimal temperatures and pressures and is only 1 part of it. Kinetics determines reactor size and type. And a lot more... It's much more physics than chemistry.

I've always felt that researchers-&-engineers (physical, chemical, biological, medical, all disciplines) contributed much more to human technology and progress, than those involved in the finance/banking/investment/economics/management industry (no offence to anyone from those industries, this is just a personal opinion).

 

The unfortunate trend of developing societies, in Asia, in Singapore, is that more youths are attracted to the 'glamourous image' or 'big quick bucks' of finance/banking/investment/economics/management, and we've seen a dramatic decline in number of applications to the engineering sciences (in NUS, NTU, and universities across the world), and a corresponding dramatic increase in applications for the finance/banking/investment/economics/management courses and professions (SMU, SIM, etc).

 

In part, this misguided, delusionary mindset ('glamourous image' or 'big quick bucks'), contributed (both directy and indirectly) to the massive world economic & financial collapse of 2008. But my concern is that it does little to change the unfortunate mindset of young students, who see the finance/banking/investment/economics as a get-rich-quick-big-bucks route, while the research-&-engineering sciences lose much needed talent as a result, and consequently the technological progress of humanity is compromised and tragically slowed down.

 

 

Again, no offence meant to anyone. I just hope to encourage passion (for the sciences) in students on these forums, that they may consider, at least as equivalent to, if not moreso, in terms of satisfaction and meaningfulness, the professions of medicine, teaching, research, engineering, etc, which contribute more directly to humanity's progress, as compared to simply dedicating your attention, time, life to the science of making money (essentially what the finance/banking/investment/economics/management industries are about), and usually the (real) motivation in these industries is for making money for oneself (one's clients, one's company, but ultimately for oneself), as opposed to contributing technological progress for humanity.

 

Merry Christmas!

 

Originally posted by Uraniumfish:

In JC websites they say what subjects are available at H1, H2, H3 levels. What is this thing all about?

http://www.seab.gov.sg/SEAB/aLevel/intro.html

 

In 2006, a new A-Level curriculum was introduced in the Junior Colleges and Centralised Institute. Since breadth of learning and flexibility are key elements in the revised syllabus, it is important that the A-Level examination changes in tandem to support that breadth and flexibility. To this end, the Ministry of Education, the University of Cambridge Local Examinations Syndicate and the Singapore Examinations and Assessment Board worked together to redesign the examination so that subjects can be taken at three levels: H1, H2 and H3.

 

H2 is equivalent to the previous Singapore-Cambridge GCE A-Level subjects in terms of academic demand and rigour. An H1 subject has about half the content of H2, but the content would be studied to the same depth as it is at H2. An H3 subject, which is an extension of an H2 subject, entails an in-depth study of a particular area that the student has the ability for and a passionate interest in. For instance, an H3 subject could involve the study of more advanced content of an existing area of the H2 curriculum, or it could be a research essay, or even a module offered by a university.

 

This tiered structure allows students to choose the levels at which they wish to study their various subjects, and thus provides the opportunity for them to achieve their personal peaks of excellence.

 

In order to achieve an optimum workload, students sitting the A-Level examination offer a mixture of compulsory and optional subjects. Other than the core H1 subjects, Mother Tongue Language, Project Work and General Paper, the typical student also offers three H2 and one H1 content-based subjects, one of which is a subject from a contrasting discipline. This will provide the student with a broad base of learning and is in line with the multi-disciplinary approach to study at university.

 

The more able students who have the passion for a particular subject and the time to manage workload beyond the normal subject combination can offer an additional H1 or H2 subject or further specialise by offering up to two H3 subjects. A small group of the most able students may offer a new H2 subject, Knowledge and Inquiry, in lieu of General Paper.

 

http://www.seab.gov.sg/SEAB/aLevel/intro.html

Originally posted by JY:

This is what happens when you study chemical engineering... After a while everything boils down to mathematical equations :P

I suspected you were a chemical engineer - you guys have an unavoidable intimate love relationship with thermodynamics.

Is your work also equally involved with organic chemistry? Do you lean more towards thermodynamics or organic chemistry (academically, professionally as well as by personal preference)?

 

 

 

Originally posted by deathmaster:

rgding qsn 30, why isn't the answer A? A contains a benzene ring, and i don't think that is manufactured in the body.

q35, yes, although both anion and cation are isoelectronic, it should not be forget that the anion has less protons compared to the cation, thus, there's more electron shielding comparatively to the anion. if option 2 make sense, by right option 3 shd be right as it too make sense.

q36. if X2 is the most reducing, isn't it the least oxidising?

 

>>> q35, yes, although both anion and cation are isoelectronic, it should not be forget that the anion has less protons compared to the cation, thus, there's more electron shielding comparatively to the anion. if option 2 make sense, by right option 3 shd be right as it too make sense. <<<

 

If the two species are isoelectronic, it means that they have exactly the same shielding effect (mostly from inner electrons shielding (shielding = inter-electron repulsion reducing the attractive effect of nuclear charge) the outer or valence shell electrons, and also a little shielding shielding effect from inter-electron repulsion between electrons in the same or valence shell). Therefore, any difference in ionic radius, must only be due to the only difference between the two species - the no. of positively charged protons in the nucleus.

 

 

 

>>> q36. if X2 is the most reducing, isn't it the least oxidising? <<<

 

Distinguish between halogen and halide ion.

F2 is the strongest oxidizing agent, and F- is the weakest reducing agent.

I2 is the weakest oxidizing agent, and I- is the strongest reducing agent.

The reason is due to the number of electron shells, hence the distance between the +vely charged nucleus and the valence shell, and therefore the ease of gain of electrons (for halogens) or the ease of loss of electrons (for halide ions).