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Archive for October 2013

See: https://intechemistry.wordpress.com/2013/09/08/chm412-topic-3-aromatic-compounds/

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The document relates to the % yield calculations.

CHM 556 note by Mr Allan 22-10-13

If you can’t figure out the acid catalysed reaction, an internet search should find a number of useful references. That’s enought help already.

Now that you have become a little bit more familiar with the lab(s), I will introduce the following penalty from next week…

If you do NOT finish the lab session BEFORE the timetabled end time, you will receive a 20% penalty for your lab mark minimum, increasing by 10% every ten minutes.

Remember Thursday CHM412 lab starts after solat Asar.

Other note: I will post the synthesis of alkenes (via dehydration of alcohols) mechanism talk-through later as well as comments about the IR spectra of 4-methylcyclohexene.

Please do the following:

Use the cover sheet provided HERE. Obviously fill it in (handwriting OK) accordingly.

  • No need to write introduction IF already given to you (in the lab manual/sheet).
  • No need to write theory IF already given to you in the lab manual/sheet.
  • No need to write the procedure/method IF what you did was the same as the procedure you were given in the lab sheet/manual.
    But
    If you did something different or extra then write down what you did.E.g. “Two distinct layers were slow to form in the separating funnel, so more volatile solvent was added and conc NaCl solution was added to the water layer.”E.g. “When drying the organic layer the solvent evaporated  so couldn’t be filtered, hence an extra 30ml of the solvent was added to the Na2SO4 drying agent.”E.g. “The final product was so small and unmanageable (a fine coating on the glass) that the whole experiment was repeated but using twice the amount of reactants in the beginning.”

    etc….

You can therefore write in your report:
Theory: as in CHMxyz Experiment pqr lab manual
Procedure/Me thod: as in lab manual – no alterations made. [If in fact you did not make any alterations]

I am interested in OBSERVATIONS and RESULTS and what CONCLUSIONS you can make from the results.

E.g. of Observations: Small bubbles of an unknown identity were were seen even after the recommended time to complete the reaction had passed.

etc.

When reporting chemical test observations state what you have in the beginning AND at the end.
E.g. Uknown colourless liquid added to purple coloured KMnO4 solution. The MnO4- solution decolourised and black solids were seen.

Results & calculations:

Make sure you PRESENT THE RESULTS CLEARLY.  Describe clearly what some value is.

E.g.
Approximate melting point range  [Fast heating] = 130oC(started melting) – 134oC (finished melting)
Accurate melting point range  [slow heating] = 129oC(started melting) – 130oC (finished melting)

mass of filter paper (a) = 1.7434g
mass of watchglass (b) = 43.3450g
mass of  mass of filter paper, watchglass and compound (c) = 46.2221g [oven dried]
so mass of compound = c -(a+b) = 46.2221 – (1.7434 + 43.3450) = 1.1337 g

Molar mass of studophene (e) = 236 g/mol
density of studophene (f) = 0.942 g/ml
Volume of studophene used (g) = 15.0 ml
so mass of studophene used (h)= f x g =  0.942 x 15.0 = 14.13g
so moles of studophene (i) = h / e =  0.0599 moles

etc…

Results MUST be signed by me (or my assistant if I have one), and you must submit the original signed results with your report. Students should submit separate reports that have not been copied, you MUST submit original work.

Conclusions:  In the conclusions you NEED TO COMMENT ON YOUR RESULTS.

E.g. The % yield should not have been greater than 100%. Out value of 320% could have been due to liquid impurities in teh liquid product, and was perhaps the silvent used. The NMR spectrum of the compound confirms the presence of the imputiry.

E.g. The theoretical melting point of 133oC is 4 oC higher than the value from experiment, suggesting the experimental sample is not pure as impurities depress melting point. [mpt source: Chempedia URL]

E.g. The synthesis of studophene from studanol takes place in high yields of 80%

Conclusions can also propose improvements on the experiment, but generally the procedures are well known and work.

Alkanes and Alkenes latest ppt uploaded.

OK. The Main CHM412 page is no longer a sticky.
You can access it using the menu’s on the right.

I want to say this…

Please, when in lecturers, do not just sit there listening to me. Although you may understand at the time, or think you understand me at the time(!!!), it is very likely that very soon after (maybe even after just a day or so) you will begin to forget bits and pieces of what I said.

Holes will appear in a continuous chain of logic that featured in a description of some process or phenomenon and the whole chain of knowledge will begin the path of decay, Meaning that you will have to learn the topic again from the very beginning, almost as if you never attended the class at all!

Only when you become stronger in chemistry then simply listening to information it it’s not too hard for it to stay in your mind (although making notes is still the best thing to do) because your brain is able to connect the issue to previously stored inforamtion. Think of a jigsaw puzzle. The experienced chemist has a lot of the puzzle already solved. Any remaining pieces and parts of the picture are easily identified and slotted in to the existing picture. To the inexperienced chemist, you are likely just to have started the jigsaw puzzle and are faced with random pieces that are very hard to connect, and take a considerable effort to do so.

Unless you actively engage in the information being given – e.g after class re-read the notes  < It is important to do this quickly preferably on the same day of the lecture. Evaluate your understanding of it, list things you don’t understand and things you do understand (the syllabus is great for this – keeping a record of what you know/understand and what you don’t!!!) go away and read the subject expecially the aspects you don’t quite understand. Try and rewrite your notes – or made additional notes.

Relying on ‘raw’ or nearly raw powerpoint slides is a poor way to go about things. Consider powerpoint notes to be just a summary of what you need to read about.

You MUST INTERACT with the information.!!! write down keywords, keyphrases and v.brief summaries of what I say in the class. Often they will help you understand something on the slide.

This isn’t school anymore. The expectation is that you don’t just learn in the class session. No! You use the class session to realise what YOU must go and learn about. The emphasis is very much on YOU, the student, to learn. That’s a key difference between university and school. At Uni YOU are the master of your own ‘knowledge destiny’.

Students have NEVER had it so good – especially at the more simple levels of learning as YouTube contains tens of excellent video’s that you can use as a springboard to understanding. But really, you must also read a book.

LEARNING BECOMES MUCH, MUCH EASIER WHEN INFORMATION BECOMES CONNECTED WITH OTHER INFORMATION

And remember…

While you think you may know something, it’s doing practice questions that REALLY shows whether you have learned those knowledge skills (and can apply them) or not.

Do the Q’s in your books and past years tests/exams and so forth.

If you do this as well as the other common good student practices of course – like dedicated study time, making study timetables etc then you succeed and be a worthy chemist indeed.


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