chem4noobs

2007-07-09T04:32:00.000+08:00

Chemistry of Radicals

A radical is an atom or group of atoms that has an unpaired electron (i.e. it has an odd number of electrons). Radical (sometimes called free radicals) are highly reactive and are intermediates in many reactions of alkanes (such as halogenation of alkane). They have the same number of protons and electrons, so they are electrically neutral (unlike cations or anions).

Radicals are all around us,even molecular oxygen (O2) is itself a di-radical. Radical reactions are of vital importance in biology and medicine because they are produced in the normal course of metabolism. An example is nitrogen monoxide (NO). In its free form, NO is a relatively unstable and potentially toxic gas. In biological systems, it is involved in blood pressure regulation and blood clotting, neurotransmission, and the immune response against tumour cells.

Because radicals are highly reactive, however, they are also capable of randomly damaging components of the body. Many forms of cancers are thought to be the result of reactions between free radicals and DNA, resulting in mutations that adversely affect the cell cycle, leading to malignancy. Some of the symptoms of aging such as atherosclerosis (hardening of the arteries) are also attributed to free-radical induced oxidation of many of the chemicals in the body. Radicals in cigarette smoke have been implicated in inactivation of an antiprotease in the lungs leading to the development of a chronic lung disease, emphysema.

Radical reactions are commonly used in many industrial processes. They are used to produce a whole class of useful polymers such as polyethene, Teflon and polystyrene. Low-density polyethene (LDPE), for instance, is produced by the radical mechanism using organic peroxide (R-O-O-R) as an initiator. Radical reactions are also central to "cracking" an industrial process whereby large hydrocarbons are converted to smaller useful molecules (such as gasoline and other fuel).

2007-04-29T07:27:00.000+08:00

It is a Bond. Not James Bond but a BANANA BOND.

Diborane (B2H6) is a molecule containing four terminal and two bridging hydrogen atoms (oso known as hydrides). The bonding between boron and the terminal hydrides is fairly conventional. However, the bonding between the boron atoms and the bridging hydrogen atoms is unusual. Having formed two covalent bonds with terminal hydrides, each boron has one electron remaining for additional bonding. The bridging hydrogen atoms each provide one electron each. Thus the B2H2 ring is held together with four electrons. The bonding between the boron atoms and two bridging hydrides of diborane is an example of 3-center-2-electron bonding (3-centre because of 2 B atoms and 1 bridging H atom sharing 2 electrons). This 3-center-2-electron bond is sometimes called a 'BANANA BOND'.

2007-04-20T22:19:00.000+08:00

Shape of [SbF5]2-

Antimony, Sb, is in Group V of the Periodic Table so it has 5 valence electrons. Fluorine, from Group VII, only requires one electron through formation of 1 covalent bond to fulfill octet. Thus, all the 5 electrons of Sb are used to form covalent bonds with the 5 F atoms. Not forgetting that the ion has an overall charge of -2, i.e. there is an additional lone pair of electron on Sb. Thus, [SbF5]2- having 5 bond pairs and 1 lone pair has a square pyramidal shape.

It is just a waste of time! Don't you get it, chicky!

2007-04-17T20:26:00.000+08:00

Just completed marking JC1 H2 Test 1.

For 07S19, majority of them did pretty well. Not really because they were good but rather the test was easy. Never in the history did we set such an easy paper on Atoms, Molecules and Stoichiometry and Redox. For the calculations, it was very guided. As part of the effort to stretch students with higher ability, we had included bonus mark question (modified from S Paper), but not many students attempted it. 07S19 has potential to do well. But many of them are complacent and not putting enuff effort. I really hope tat the weaker students will catch up with the better ones soon.

For 07S12, the performance was really bad. Only 4 passes. I can understand that many of them do not have strong foundation in Chemistry. That is why I arranged for an extra lesson on Saturday to give them extra coaching on mole calculations and redox. But it turned out to be a total waste of time. Mainly because the students did not even prepare for the lesson. Throughout that two hours, they were just copying the answers. They failed to realise that they would not understand a single thing unless they processed it through thinking and working.

I am really worried about the coming SPA for 07S12. But I doubt they are. It is my first time having to "beg" students to submit their practical file for marking. I dunno why m I doing this for students who cannot be bothered.

I always believe that practical can help reinforce wat students learn in theory. With the good intent, I planned for practicals on Chemical Energetics for my JC2 H1 students. Once again, it turned out to be a plain waste of time and effort because my students were not at all interested. They questioned me why they were doing experiments. They questioned me why they needed to plot a graph (not as if they will be tested in A lvl Exam). They asked me "can don't do anot". The only consolation I got was that the Arts H1 students (under Mr Tong) were very engaged during the practical and they looked forward to it.

I am trying very hard to improve on the standards of our students but wat I get is disappointment. Maybe I m not suited for this place. It is time to look for other alternatives. The push factor is just too great. Getting more sick and tired.....

Release of 'A' Level Results

2007-03-03T05:55:00.000+08:00

The wait was finally over as the 2005/06 cohort received their GCE 'A' Level results yesterday. For many, I guessed it was a day to rejoice as our college results improved tremendously from the previous year.

On the whole, Chemistry improved in terms of passes (up by 0.4%) and number of As (up by 7.5%). I owe it to the team of JC2 teachers for their dedication and hard work.

For my classes (05S01, 05S06 and 05S08), I congratulate you for your outstanding performance in Chemistry. All your hard work indeed paid off. U pple have given me renewed motivation and strength in teaching. I thank you for being such great students for the past 2 years. I hope that you can give me some candid feedback on my lessons so that I can be a better sensei.

Now equip with a passport, I hope you will consider the journey to embark on very seriously. Do visit the Career Exhibition 2007 in Suntec (1 - 4 March) to find out more about the university courses and the career prospects. Please feel free to come back to us if you need advice. For those of you who did not perform that well in A Levels, dun get too upset since you have done your best. As mentioned by Mdm Shafa, you are definitely more than those alphabets on your results slips. I hope you dun see it as an end to your education. There are other alternatives out there and I am sure u can find something suitable.

I wish u all the very best in your future endeavours. Take care and keep in touch.

A New Year Ahead

2007-02-19T09:15:00.000+08:00

It has been moons that I last updated the blog. Ever since the end of A lvls last year, this blog seems to have lost its purpose. I guess it shall continue to serve as a means of communication with the noobs I taught last year. Hopefully, its readership can go on with this new batch of students I am currently taking.

As of now, I am taking two JC1 H2 classes (07S09 and 07S13) and one JC2 H1 class (06S10 and 06S19).

For the two JC1 classes, dun really feel very attached to them unlike the classes I took two years back. Probably, the time they are with PJC is shorter. Lesson time is also reduced. What's more, students are not really focused. I look forward to the JAE results to be out, so that I can get down to serious teaching.

Just took over the JC2 H1 class in week 3. Din expect to straddle this year and dunno if it is a good choice. The class as a whole is nice to teach. A lot of interesting characters who will spice up the lesson. However, results of the first test seem somewat disappointing. Some hv underperformed as compared to last year. Really hope that they will be more focused and disciplined in preparing for the coming Common Test.

Pretty worried and anxious about the A lvl results for last year's cohort. I guess it is going to be out in one to two weeks time. Hope they all will do very well and move on.

As for myself in 2007, I look forward to complete the rollerblading course for noobs and hope to get a place to do my Masters in July.

Preparation for Paper 1

2006-11-14T18:35:00.000+08:00

Hope that all of u r surviving well. I think the paper 2 and 3 are quite manageable lah. What really makes a difference in yr grades is how careful u were when u attempted the questions and not forgetting the quality of your answers.

To prepare for Paper 1, make sure u practise as many questions as possible from the TYS because some questions tend to repeat. Do the yearly papers at the back of yr TYS then move on to the topical questions. Pay more attention to topics that hv not been set for Paper 2 and 3, namely Atomic Structure, Energetics, Solubility Product, Group II and Polymerisation. Look through yr Common Test, Mid Year Exam and Prelim Paper 1 as well.

On the day of the exam, remain calm. Read the questions and select your answers carefully. DO NOT LEAVE BLANKS. You have only 1 min 30 sec for each question, manage your time well.

That's all I have for u pple. I hope I have prepared all of u sufficiently for the A level Examinations. As I will not be around on Friday, I wish all of you the best for your Paper 1.

Things u should noe (Part 3)

2006-11-06T20:10:00.000+08:00

1) No units for Ar and Mr (since they are ratio of 2 masses). Relative formula mass of an ionic compound is the same as Mr of the compound; no units too. Units for molar mass is g mol-1.

2) To prove 1st order reaction by the continuous method, it is recommended that the half life method is used. Construction lines must be clearly drawn to show that the two half-lives (not necessary consecutive half-lives) are constant with the half-lives stated.

3) Autocatalysis is a type of catalysis whereby one of the products of the reaction catalyses the reaction. (See lecture notes and page 119 TYS question 6)

An example is the reaction between manganate(VII) and ethanedioate ions in acidic medium. Mn2+ formed acts as a catalyst for the reaction.
The rate of such a reaction is slow at the beginning of the reaction (since there is hardly any catalyst).
As the reaction proceeds, concentration of Mn2+ increases the rate of reaction increases.
The rate of reaction will eventually decrease as concentration of reactants decreased to very low levels despite the increasing concentration of the catalyst.

4) When calculating rate constant, make sure u give the correct units based on the overall order of the reaction. Note that rate constant and rate is always positive or zero (never negative).

5) When drawing reaction pathway diagram (or commonly known as energy profile), make sure u label the two axes with the y-axis labelled "energy". There should be two horizontal lines, one labelled "reactants" and the other "products". Include the activation energy as well as the enthalpy change of reaction if the data are provided.

6) Activation energy is the minimum energy reactants must possess in order to overcome the energy barrier to form the products.

7) A catalyst increases the rate of a chemical reaction by providing an alternative reaction pathway with lower activation energy. This results in an increase in number of particles having energy greater or equal to activation energy, thus increasing the number of effective collision per unit time. Note that a presence of a catalyst will increase the rate constant but NOT the equilibrium constant.

8) The bond in O2 is a double bond, i.e. O=O. So make sure u quote the right bond energy when calculating the enthalpy change of atomisation for oxygen.

9) Bond breaking is endothermic and bond formation is exothermic.

10) For some definitions, if u r not sure of how to write in a statement, u should give the mathematical expression instead. For example, pH is the negative logarithm to base 10 of the concentration of H+ can be given as pH = -lg[H+].

11) In the electrolysis of brine, the purpose of the asbestos diaphragm is to prevent mixing of the products (Cl2 and NaOH). Thus, it prevents Cl2 from undergoing disproportionation in NaOH(aq) to form NaClO(aq) and NaCl(aq). Note that the diaphragm cell operates at relatively low temperature, NaClO3 is not formed.

12) Sodium hydroxide is used in making of soap (via saponification) and detergent, used in refining aluminium oxide and for manufacturing pulp, paper and textile (rayon - artificial silk). Note: the use of NaOH(aq) in school and college laboratory is NOT acceptable as a large scale use.

Chlorine gas is used as a germicide (sterilisation of water), bleaching agent (for cotton, linen & wood pulp), making polyvinylchloride (PVC used in water pipes). Note: the use of chlorine in manufacturing of CFCs is NOT acceptable.

Hydrogen gas is used in the making of ammonia (Haber Process), for the hydrogenation of fats and oil (manufacturing of margarine) and in metal welding using an oxy-hydrogen flame (2000 degree celsius).

13) For reaction of Cl2 with alkene, it is important to state the physical state of Cl2 (g, aq or in organic solvent such as CCl4) since different products will be obtained.

14) When describing colour change, there is a need to state the initial colour. E.g. Orange K2Cr2O7 turns green.

15) When analysing mass spectrum, make sure that the species are singly positively charged unless otherwise stated by the question.

16) Labile protons are found in alcohols, phenol, carboxylic acids, primary amines, secondary amines, primary amides and secondary amides.

Advice for Paper 3

2006-11-05T08:11:00.000+08:00

Make sure u have yr entry proof and EZ link card / ID before reporting to the exam venue.

Don't panic and try to calm your nerves.

1) At the start of the paper, read quickly through the paper to get a feel of the demands of each question.

2) Select the question that looks most familiar and the easiest to attempt first. A good start helps to build up yr confidence. Try to order your choice of questions in this manner.

3) For Q3 either / or (Physical Chem), Q5 either / or (Inorganic Chem) and Q 8 either / or (Organic Chem), it is important look through both questions carefully before making your choice. Note that it is unlikely that u have time to change to another question after u start working on one.

4) Note that u have 15 minutes for each question. Organise your time effectively. For any parts which u dunno what to do, move on the the next part and come back to it later. Remember to leave sufficience space for questions which u hv skipped. All answers (except for graph work or diagrams such as Boltzmann distribution) must be given in blue or black ink.

5) Make sure you read the question carefully, make sure that u r answering the question. Check twice - a second spent here can save a lot of time later.

6) Do write out your answers in neatly and show your workings clearly with proper statements.

7) Do use diagrams in your explanation.

8) On completion of a question, do read through the question again to make sure that (a) you have not omitted any part of it, (b) all diagrams and graphs are properly labelled (c) final answer is given to 3 significant figures and (d) units are stated (e) signs are given for oxidation states, enthalpy changes and electrode potential.

Things u should noe (Part 2)

2006-11-05T06:44:00.000+08:00

Some comments based on June 2006 Paper [Make sure u look thru the paper, similar questions may be set for A lvls.]

1) Besides using NaOH(aq) to test for presence of metal cations, it is also used to test for presence of ammonium ions. The ammonium ion (a conjugate acid of ammonia) will react with hydroxide ions to give ammonia gas and water (no heating is required as it is an acid-base reaction). Ammonia liberated will turn moist red litmus paper blue. Ammonium ion can be from an inorganic salt e.g. ammonium sulphate (NH4)2SO4 or from an organic salt e.g. ammonium ethanoate CH3COONH4.

2) When using the general gas equation pV = nRT, make sure that p is in Pa, V is in m3, n is in mol and T is in K. Note that 1 atm = 101000 Pa.

3) The reactions of conOcentrated sulphuric acid with solid magnesium halides are the same as those of sodium halides.
For magnesium chloride, white fumes of HCl will be produced.
MgCl2(s) + H2SO4(l) -----> MgSO4(s) + 2HCl(g)
For magnesium bromide, reddish brown fumes of Br2(g) are produced. Note that SO2 which is formed is a colourless gas with an irritating smell. This may not be observable as it may be masked by that of Br2(g).
For magnesium iodide, violet fumes of I2(g) are produced. Note that H2S which is formed is a colourless gas with the smell of rotten egg. This may not be observable as it may be masked by that of I2(g).

4) Hot, acidified K2Cr2O7 does not cause oxidative cleavage of alkene or side chain oxidation of benzene.

5) A substitution reaction is one in which an atom or a group of atoms of a molecule is replaced by another atom or group of atom. For example, in the nitration of benzene, one hydrogen atom is replaced by -NO2 group.

6) Oxides of nitrogen (NO or NO2) are homogeneous catalyst for the oxidation of SO2 to give SO3.
NO(g) + 1/2 O2(g) ----> NO2(g)
SO2(g) + NO2(g) ----> SO3(g) + NO(g) [regeneration of the catalyst, NO]
Overall equation: SO2(g) + 1/2 O2(g) ----> SO3(g)

7) Determination of concentration of Fe(II) ions using KMnO4

Fill the burette with 0.0200 mol dm-3 of KMnO4 solution.
Pipette out 25.0 cm3 of the solution containing Fe(II) ions. Acidify solution with 10 cm3 dilute sulphuric acid.
Titrate the solution containing Fe(II) ions with KMnO4. Add KMnO4 dropwise near the end point. End point is reached when solution turns orange. Note the volume of KMnO4 used.
Repeat the titration until consistent results are obtained (within 0.10 cm3)
Average titre value should be taken for the calculations.

Things u should noe (Part 1)

2006-10-28T18:21:00.000+08:00

1) For principal (correct spelling) quantum number n = 1, there are 1 subshell (s) and 1 orbital.
For principal quantum number n = 2, there are 2 subshells (s and p) and 4 orbitals.
For principal quantum number n = 3, there are 3 subshells (s, p and d) and 9 orbitals.

2) For electrochemical cell, the polarity of the anode is negative and the polarity of the cathode is positive. For electrolytic cell, the polarity of the anode is positive and the polarity of the cathode is negative. For both type of cells, the flow of electron is always from the anode to the cathode.

3) Only alcohols with CH3CH(OH)- and carbonyl compounds (aldehyde and ketones only) with CH3CO- will give yellow precipitate of CHI3 with alkaline aqueous iodine. Carboxylic acids and its derivatives (e.g. CH3COOCH3) will NOT give a positive result.

Farewell Assembly

2006-10-12T22:29:00.000+08:00

This important day marks the end of your JC education. I think it is meaningful to look back at how you spend your two years in college. I am sure there are meaningful and unforgetable moments. Do make a point to thank your friends and teachers who have walked through this journey with you.

To all my students, I really enjoy the lessons with you. I find my sense of purpose and drive to do more for you pple. I hope you all have benefitted from my lessons. Do give your feedback on my lessons so that I can improve as a sensei.

For this crucial part of yr quest, be rest assured that I will be there for u pple. Do come to me if you need help. Study hard but must take good care of yourself. Have more confidence in yrself tat u can do it and can definitely do it well.

I wish each and every one of u the best for the coming A lvls. Hope you will do yrself, yr parents and yr college proud when you receive yr results next year.

What a day!

2006-10-06T20:52:00.000+08:00

I was rather frustated marking S01 post prelim test 1 scripts in the morning. Realised that even S01 is not ready for the A lvls. Simple questions like finding empirical and molecular formula, writing electronic configurations, colour of aqueous iron(II) and iron(III) ions, explanation for why aqueous iron(II) is coloured could not even do. What was going on? No one from S01 came to ask for consultation. If only they are really tat good. I emphasised repeatedly about the need to write proper statements. All i get are crap such as "Aldehyde. A gives a silver mirror upon adding Tollens' reagent." How do u pple expect the examiners to understand yr explanation and deductions? I think I have done my best for u pple. Nothing can help u unless u want to help yourself. Two years back, I can confidently name my potential A students. At this juncture, I really have little confidence about anyone scoring an A. Results are not consistent, fluctuating more than the share market. Haiz.

Lesson with S08 was normal, going thru the post prelim test. Can see that most of the S08 pple are working very hard. I was really impressed with the improvement of the prelim results. Keep up with the good work and I m sure u all can do better. For those of u who put in a lot of effort but not seeing the results, not to worry. Very seldom u see instantaneous results and that is the main difference between O lvl and A lvl. If u perserve, u will enjoy the fruits of your labour eventually.

Was invited to Ms Xiao's birthday party organised by S06. Really had a good time. U pple r really talented, particularly Matthew who was the emcee. Almost kena sabo by patrichio and company to sing tat "huo huo huo" song.

Remedial for the F students was rather slow. Need to really speed up the next lesson so that we can cover more topics. Hope that the session is beneficial to the students. Do give your feedback concerning the remedial lessons.

Ok, very tired liao.... Time to hit the coop.

Preparation for Paper 1 and 2

2006-09-16T14:13:00.000+08:00

Having marked Paper 3 Q7 and Q8 either / or of some classes, I came to realise that some of you cannot handle the questions. I dun think it is because u are ill-prepared or have not put in enuff effort, but rather, u cannot perform under examination conditions. I can see a lot of careless mistakes in your answers. I hope u will learn to be calm and read the questions carefully. Dun rush into giving answers without thinking. Anyway, continue to work hard for yr remaining two papers.

For those sotongs, there is no food chem for paper 1 and 2. So dun revise food chem hor.

For Paper 1, it would be helpful to practise mcq questions from TYS or Prelim Papers during the weekend. If u face with any difficulties, can consult via msn or see me on Monday. On Monday, please go thru questions which u made mistakes in JC1 and JC2 tests and examinations. No point doing more questions on Monday.

For Paper 2, you should focus on topics that had not been assessed in Paper 3. However, that does not mean that questions cannot be set from the topics that had already been tested. I would also advise that you learn up your reagents and conditions for the various organic reactions (quite badly done in Paper 3). Remember to go thru your test and exam papers if u had not done so.

A few more days only. Continue to work hard and I am sure u will be able to make it. Gambatte!

Performing experiments in the cyberspace

2006-09-07T18:07:00.000+08:00

For those of you who did not pay attention during QA practical lessons and would like to have a try at the experiments again, here is yr chance. Want to introduce a website to u pple.

http://neon.chem.ox.ac.uk/vrchemistry/LiveChem/transitionmetals_content.html

The following reactions are more relevant to yr syllabus. You need to know how to account for the observations. Refer to yr QA notes if u r in doubt.

1) chromate(VI) + dilute hydrochloric acid [conversion of chromate(VI) to dichromate(VI) - not a redox reaction]

2) dichromate(VI) + sodium hydroxide [conversion of dichromate(VI) to chromate(VI)]

3) iron(II) + sodium hydroxide [formation of green ppt - iron(II) hydroxide]

4) iron(II) + dilute & concentrated ammonia [formation of green ppt - iron(II) hydroxide]

5) iron(III) + sodium hydroxide [formation of brown ppt - iron(III) hydroxide]

6) iron(III) + dilute & concentrated ammonia [formation of brown ppt - iron(III) hydroxide]

7) iron(III) + potassium thiocyanate [special test for iron(III) ions - forming blood red complex]

8) copper(II) + sodium hydroxide [formation of blue ppt - copper(II) hydroxide]

9) copper(II) + dilute & concentrated ammonia [formation of blue ppt, followed by soluble tetraamminecopper(II) complex which is deep blue in colour]

10) copper(II) + edta [complex formation - note that as edta^4- is a hexadentate ligand]

11) copper(II) + concentrated hydrochloric acid [note that the solution turns green becos of the presence of the blue hexaaquacopper(II) complex and the yellow tetrachlorocuprate(II) complex]

12) zinc(II) + sodium hydroxide [formation of white ppt - zinc hydroxide]

13) zinc(II) + dilute & concentrted ammonia [formation of white ppt, followed by soluble tetraamminezinc(II) complex]

Feel free to try out other reactions. Particularly safe for "laboratory terrorists" and "lords of destruction" - u noe who u r. Have fun.

Alloys

2006-09-06T08:23:00.000+08:00

An alloy is a mixture (not a compound) of two or more metallic elements (sometimes carbon is also used). Some common alloys u need to know are brass, bronze, steel and stainless steel.

Brass (60 - 80% Cu; 20 - 40% Zn)
Use for making moving parts of clocks and watches, nuts, bolts, rod tubes, musical instruments and ornaments.

Bronze (90 - 95% Cu; 5 - 10% Sn)
Use for making coins, medals and sculptures.

Steel (98 - 99.5% Fe; 0.15 - 1.5% C)
Construction of bridges, ships, cars and machinery.
Note: steel cannot be used as a anode for electrolysis of brine because the iron reacts readily with the chlorine produced, forming iron(III) chloride.

Stainless steel (90 - 95% Fe; 5 - 10% Cr, Ni)
Use for making cutlery, tools and surgical instruments.

Uses of products obtained from electrolysis of brine

2006-09-05T09:10:00.000+08:00

The electrolysis of brine (concentrated NaCl) yields the following products.

Cathode: Reduction of water takes place, producing hydrogen gas and sodium hydroxide.

Hydrogen gas is used in the making of ammonia (Haber Process), for the hydrogenation of fats and oil (manufacturing of margarine) and in metal welding using an oxy-hydrogen flame (2000 degree celsius).

Sodium hydroxide is used in making of soap (via saponification) and detergent, used in refining aluminium oxide and for manufacturing pulp, paper and textile (rayon - artificial silk).

Anode: Oxidation of chloride (due to its high concentration), producing chlorine gas.

Chlorine gas is used as a germicide (sterilisation of water), bleaching agent (for cotton, linen & wood pulp), making polyvinylchloride (PVC used in water pipes NOT NON-STICK PANS *faint*).

Btw, the polymer for making non-stick cookware is poly(tetrafluoroethene), PTFE a.k.a. Teflon.

A Big Thank You ....

2006-09-05T08:48:00.000+08:00

A big thank you for your Teachers' Day gifts and dedications.

Really hope that all of you will give your best for this last lap. Can see that pple in S08 are working hard (and working me real hard too). Gambatte! All the best for your prelims! :)

Disappointing chemistry test results

2006-08-20T23:05:00.000+08:00

After spending so much time on revision for energetics and kinetics, you are still not getting it. Why?????

We have done so many questions on Born Haber cycle to calculate lattice energy. Just becos you are provided hydration energies of the ions, some of you actually incorporated it into the cycle. What is wrong with u pple?

Kinetics. Having said ample times, pple r still not showing the half-life on their graph. Is it really tat difficult to accomplish? Still, I have pple applying half-life concept to overall second order reactions. Not to say the explanation of effect of temperature on rate of reaction - key points not there and not labelling the Boltzmann distribution curve.

Organic equations r not balanced. Pple r giving answers in pencil.

All I can say is that I have done my best. I dun understand y i m more worried than some of u. Completely drained and demoralised.

2006-08-16T20:59:00.000+08:00

Do you know …

1 Standard enthalpy change of atomisation for elements is the energy absorbed to produce 1 mole of atoms under standard conditions.

2 Standard enthalpy change of atomisation for compounds is the energy absorbed to convert 1 mole of substance into atoms under standard conditions.