mak10

i dont know if i can explain electode potentials in a nutshell (you need to have fairly good idea about redox chemistry for which u can refer to any good advanced chemistry textbook) but let me give it a shot any feasible set of reactions that take place, either involves loss (oxidation) or gain (reduction) of electrons. thus all reactions have an electrode potential value, which can be positive or negative, determined by electrolysis reactions (for details how its done, see here but be prepared for some agnozing moments!). if a reaction has a positive EP value, the forward part of the reaction, i.e - the product side, is more stable than the backward part, i.e - the reactant side, that is to say that the position of the equilibirum lies to the right. its the other way round if the EP is -ve. example: 1) Mg2+ + 2e- ===> Mg [EP = -2.37] 2) Cu2+ + 2e- ===> Cu [EP= +0.34] the EP of the 1) reaction shows that the position of the equilibrium lies to the left, i.e - Mg2+ does not get easily reduced to Mg. the EP of 2) reaction shows that, compared to the EP of Mg2+, the position of equilibrium of copper lies to the right, i.e - the Cu2+ is almost fully reduced to Cu, since its easier, as the EP predicts. Similarly, the EP of the reaction, CH3COOH <==> CH3COO- + H+ is probably negative, hence the position of this equilibrium lies well to the left, as un-ionised ethanoic acid molecules, which is why its a weak acid. other factors such as the delocalisation of negative charge by oxygen lone electron pairs over the ethanoate ion "pushed" by the alky group attached (as they are an electron donating group), attracting the positive hydrogen ion and thus re-forming the un-ionised molecule most easily... are also important in determining the negative EP of the reaction. here are some links u can go through to learn more, if u're interested in electrode potentials and the chemistry involved: http://au.encarta.msn.com/encyclopedia_761569809/Electrochemistry.html http://www.physchem.co.za/Redox/SEP.htm http://www.pinkmonkey.com/studyguides/subjects/chem/chap9/c0909601.asp well, there is 1 mole of ch3coo- and 1 mole of h+ in the ch3cooh molecule, by the reaction equation... but i am talking about how much of ch3coo- and h+ are ionised during the reaction... and out of the 1 mole, only 0.01 moles of H+ and 0.99 moles of ch3coo- are probably ionised at any one instant of time. oxygen, in its un-ionised/neutral state, has to form two bonds.... so h is written in the cooh to indicate that one oxygen has formed double bonds with carbon and the other has formed a single bond with carbon and a single bond with hydrogen. you are confusing the ionisation of an acid in an aqueous solution with their dissolution in dilute solutions. remember, the partially +ve end of the water is still H+. -mak10

am doing my a-levels currently in bio/chem/phy and cant make up my mind whether to opt for pharmacy (concentrating on pharmacology) or getting an MD. as fas as i know, pharmacy with a concentration on pharmacology studies the effects of various types of drugs on the human body... in which case, i cant think of any difference between this and what a physician studies. someone told me that a major in pharmacology, as a premed, and then doing medicine is possible in states. is this a better option than doing MBBS directly and then MD?? thanks! -mak10

the only conditions i can think of is that the system, where the reaction takes place, must be closed/isolated system and the influx of energy, if its there, must be constant. the reaction is reversible but that doesn't mean all solutions of ch3cooh are in dynamic equilibrium. its a weak acid because it undergoes incomplete ionization, i.e - produces less H+ ions compared to ch3coo- ones.... the ratio is something like 1:99. and whether a reaction proceeds fuly forward or backward really depends on its electrode potential, whether oxidation or reduction is the chemical reaction's forte... i think. i can explain the latter in detail if u're interested... pardon me but i don't exactly understand what u're asking here. the formula is ch3cooh and yes, the positive ion is H+... so why doesn't the formula start off with the positive ion?? u can have ch3cooh as h3ccooh, but u certainly cannot have it as h4ccoo... the h of the coo which forms the positive ion must be with coo which must be written with, if not after, ch3. but u can write it as hoocch3... as long as the h+ is with the coo. and i don't recall any rule strictly stating that all formulae shud start off with the positive ion.... and even if there is, as per ur teacher, i highly doubt it being applicable to organic compunds like ethanoic acid. anything which reacts with an acid is a base and bases that are soluble in water are alkalis. -mak10

correct... it really depends on the bondings in the molecule. for example, methane CH4 is a sp3 hybridised molecule, i.e - the carbon in the methane molecule needs to hybridise 1 electron in the s orbital with 3 electrons in the next p-orbital (all of them being unpaired initially) in order to exchange electrons with 4 hyrogen atoms and form sigma bonds. the same goes for sp2... (work out the structure and electronic config of ethene to figure out why its an sp2 hybridised molecule ). i dont know abt s2p3 though... never heard of it, i dont know what the 2p stands... is it referring to electrons in the 2p orbital?? -mak10

speaking of medical school... i am kinda confused of the chronology of degrees you need to undertake in order to be a GP, for example. it all starts with MCAT, as I've heard... but then, I've also heard that you dont need MCATs if you've done A-Levels.... is that true? And what exactly is after MCATs?? and how many years are required to finish each of the degree courses that follows after the MCATs?? at what point of time do you get to be an MD. ?? thanks guys! -mak10

i find the subject of actually being able to synthesize drugs fascinating! you need a pharmacology degree for that, i think. but the market is too saturated with this, i reckon. -mak10

so if we can develop a drug that can increase the life-span of the average dog to that of the average man.. can it then surpass us by its 7x intelligence?? just a thought... -mak10

finally, some responses! thx guys... i asked my school, whther I can do AS-Level math but i am not allowed to take more than 3 subs... which is very annoying!! and i dunno if we can do this privately either.. grrrr!! so many decisions.... i guess it pays to think about what you wanna do in the future when you're givin your GCSEs... but i didn;t. nonetheless.... can you guys advise me on a career, that is science application-based, that is more at demand these days.... i cant seem to get a decent figure on any of the science career options! all of them appear to be saturated throughout the world! my choices right now (after narrowing down among hundreds!) are allergy/immonology specialist, psychiatrist, dentist, or just a general practitioner. are my present a-level subjects (i.e - bio/chem/phy) adequate in doing a degree in any one of those career choices? thnx again! -mak10

<bump> i really need some good advice... and its been a while i posted this and received no response yet. does anybody have trouble understanding my situation.. if so, plz inform me... thx! -mak10

what qualifications must you possess (like a BSc or MSc) to be called a nanotek expert or something? -mak10

thx skye and mokele... i just had my exams today anyways. one of the questions was similiar to 1) and it was like a polypeptide is made of 'n' number of amnio acids and there are 'r' number of different amino acids available. so what is the expression that gives the minimum number of different polypeptides possible with these variables? i think i chose r^n.... unless i remember the question incorrectly. is it right? -mak10

ok, i need some help.. some serious help! i recently undertook AS-level bio/chem/phy having done my GCSEs and i've had some pretty good grades in the latter. My former just ended today.. its all over and I think my results are gonna be published sometime in Jan. I've done rather good in physics, ok in chem and very good in bio. now... the major reason i took these subjects is because i thought there was a good life to be lived as a scientist, a biomedical engineer, perhaps... with good wage and interesting work (since i love science). and everyone advised me so. but realizing now and seeing all the entry requirements in order for a degree for the universities that I've come across.... you need a basic A-level in math too. is this true for all science application-based subjects like biomedical science, biotek, medical physicist, and almost all general engineering based fields that are closely related with bio/chem/phy ?? if so... now that I have my AS-Levels on all the above three (and I don't wanna spend another year for doing separately one subject!!)... assuming that i do very good in bio (which i really think i will), will it be wise for me to drop it for A2 and take the AS math instead?? i dont know... i am very confused... will they only accept me for their degree based on AS math (i can assure that i can do very good there, since i have a strong GCSE record) and i dont want to waste another year in unis doing foundations either. any good advise from people who've 'been-thru-and-done-that' will be greatly appreciated!! -mak10

could you explain the reasoning in q.1 ?? is there some kid of formula for these things? -mak10

I have come across certain simple questions in my MCQ past papers whose answers I am not really very sure of... so here it goes: 1) if there were 34 amino acids and DNA only contained two types of nitrogenous bases, what would be the minimum number of bases per codon that could code for proteins? 2) what single feature is correct for all enzymes? 3) A capillary tube is inserted into the phloem. what force/pressure causes the sap to flow out of the tube? 4) what proportion (in %) of the stored chemical energy in grass is converted into new tissue by a growing cow? ask me for the options if you need'em. -mak10

yes, the DNA replicates and the chromosomes again divide into two chromatids, marking the onset of interphase. this can go on an on, depending on the instructions encoded in your genes. if this instruction is disrupted (like in cancer), then the cell may start dividing uncontrollably and can form unspecialized masses canlled tumors. i don't want wanna into more detail on this but thats basically it. -mak10