However, there were times that my students would not understand what I had drawn up in the blog. Try as I might to explain everything in the simplest of terms that I could muster, they simply could not get the point that I was driving at. Maybe I am bad in explaining things. Or maybe I would just have to concede that teaching via a blog has its limitations and should thus be used sparingly as an instructive tool. It was an obvious fact and yet, stubborn as I am, I tried to reach through them using the blog. I failed miserably; there were posts where I induced more nausea than light bulbs blinking atop their heads.

This blog has outlived its purpose. I was a teacher and I used to write on this blog every week for reminders and other what-not. Now that I am not a teacher any longer, I feel that I have no use for this blog anymore. Maybe I’ll find a new use for this blog some time in the future, recreate it and turn it into something else. Or maybe I could just let it be so that 10 years later, I could proudly look back, read through the post one more time, smile and say to myself, “I was a teacher once and this is but one testimony that I tried my best to imbue my students with wonder and awe in Chemistry”

anyway, before your summer classes begin, please DO pick up your checked postlabs and lab exams on the cabinet found outside of the faculty room. unclaimed postlabs and lab exams would be disposed by the chemistry department. thus, if you would want to have some sort of remembrance of your chem lab, would it not then be a good idea to have your postlabs as memoribilia? haha.

kidding aside, i would want to thank you all for making chem 12 enjoyable. i hope you found it fun too may all of you do well in your course and if you need any help in the future, with the exception of financial and love related problems that is, just text me or message me in facebook and i’ll see what i could do to help you

god bless everyone and goodluck!

signing off,
john paul b garcia

i am not done making the test as of yet but looking at the questions that i have made so far, i have a feeling that you guys could finish the test in an hour and a half tops. with that said, i have decided to move the test from 8:30 AM to 10:00 AM on tuesday (and of course, thursday for the thursday class). i will be there in class as early as 9:30 AM and thus, if you think that 1 hour and 30 minutes would not suffice, you may start the test as early as 9:30 AM. do not get me wrong, the wager that i made with your class still stands: if i do not arrive by 9:30 AM, then the class would be rewarded :p

if you have any comments or suggestions, please feel free to email me. that is all for now

i have been told that some of you are having a difficult time figuring out how to get the % Fe of their samples. i thought that you guys would be able to easily figure it out for yourselves so i gave no clues of how to find it. anyway, without further ado, here are the so-called hints in solving the % Fe of  your respective samples.

1) before beginning, let me remind you guys to please put the bottle number of your unknown on the upper right hand side of the first page of your worksheet. this is so that i may easily check the % Fe of your unknown against the actual % Fe of the sample you worked on.

2) bear in mind what you are looking for; you are looking for the % Fe of your sample. it means that you are looking for the grams of Fe in your sample compared to the whole of your sample. % Fe = g Fe in sample/g sample.

3) work backwards. start with what you have. first up is your calibration curve which relates your absorbance with your concentration. you can then plug in the absorbance of your aliquot into the calibration curve equation in order to get the concentration of your unknown.

4) next up is the fact that you measured the absorbance of your 50 ml aliquot. it means that you could easily get the amount of Fe in your aliquot. for instance, you found out, through the calibration curve, that your aliquot has a concentration of 7.5 ppm. it means that you have 7.5 mg of Fe3+/L solution. thus, using this information, you could derive the amount of Fe in your 50 ml aliquot.

5) remember that you dispensed 5.00 ml of your unknown stock solution and then diluted it to 50.00 ml which served as your aliquot. thus, it means that the amount of Fe that you calculated to be in the 50.00 ml aliquot is the same as the amount of Fe in the 5.00 ml of stock solution that you dispensed.

6) by this step, you should already have the amount of Fe in 5.00 ml of your unknown stock solution. since you prepared 250.00 ml of unknown stock solution and you delivered only 5.00 ml, then it must mean that your unknown stock contains 50 times more unknown than the 5.00 ml that you dispensed.

7) there you have it, the amount of Fe in your unknown. you just have to divide it with the weight of your original sample (which should be around 0.1402 g), multiply by 100, and voila, you have your % Fe in your sample.

hope this helps you guys out

should you have any questions, comments or suggestions, please feel free to comment on this page or better yet, email me.

have a nice weekend guys

for chem 12 E, you should have your prelabs ready right before the scheduled experiment on tuesday. for chem 12 F,  you should have your prelabs done by tuesday, 12:30 PM.

thanks and have a great weekend guys!

1) abstract/executive summary

• this should be a summary of what happened in the experiment. you need not story-tell every detail, but at you should at least give your readers a glance of the chemistry in the experiment in a comprehensible manner.
• for instance, in the freezing point depression experiment, you could first define freezing point depression as a colligative property then introduce the concept of finding the molecular weight of an unknown through this property. give the readers the freezing points of pure naphthalene and the mixture and then use the equation related to freezing point depression in finding the molecular weight of the unknown.

2) introduction

• please refrain from using first and second person pronouns. it would be fine to use third person pronouns for the lab report, but it is best to use passive sentences without first, second or third person pronouns.
• keep the introduction short and concise but not to the point that only a list of definitions are in it.
• if you lifted something directly from a website or a book, please enclose everything in quotes and then add, in parentheses, the site or book from which the quote was lifted OR if you want, you could use footnotes instead of the ‘parentheses style’ of citing sources.
• good introductions are those that are able to discuss the experiment and its objectives in light of theoretical concepts of chemistry, either discussed in class or researched from the internet and/or books. i however prefer researches from books rather than from internet sites such as, and especially, wikipedia.org.

3) data and results

• record as many observations as you can. the more the better.
• when making qualitative observations, please be as descriptive as possible.
• keep your data sheets neat and your writing legible so that i could read your work without any ‘guesswork’.
• affix units whenever applicable. a meter and a millimeter are worlds apart.
• significant figures. always mind your significant figures. when measuring, make sure that you include all of the digits which you are certain of plus one uncertain digit.
• i might have said this for around a million times already but what the heck, let me say it again: do not blot out data. it is imperative, for reasons that i have discussed in class, that data should not be erased with white outs nor should they be crossed out fully. a single line striking the wrong data off would suffice.

4) sample calculations

• i do not need you to show me each and every calculation that you did in processing the data you obtained from the experiment. i only need to see a single calculation that would illustrate how you arrived at your results.

5) discussion

• be terse and concise. the discussion part is there to connect the chemistry principles learned in class to the experiment that was done. in case the experimental values/trends do not conform to the theory as taught in class or as researched, you are expected to explain or account for the discrepancy observed.
• sometimes, students explain observed discrepancies of experimental values to theory with errors made or inherent in the experiment. note that i would not accept a list of ‘errors’ that could otherwise be avoided in the experiment, i.e. spillage, wrong measurements, etc. as reasons for the deviation of the experimental trends to the theoretical set-up. these are human errors that could be corrected by repeating the procedure and/or by careful measurement and technique. the sources of errors that  i would accept are those that are beyond the control of the student, i.e. instrument and technique limitations, environmental fluctuations, etc.
• i do not have a minimum for the discussion part, so long as you have discussed everything that needs to be discussed. however, i do have to impose a maximum because I would be tending to 200 postlabs and thus i do not have the time in the world to leisurely read through lengthy discussions. limit your discussions to a maximum of 2 pages.

6) answers to questions

• as i have stated in my previous post, your answers to the questions should NOT be integrated to the discussion part.
• get straight to the point. using flowery words only consume unnecessary space and add nothing substantial.
• answer the question completely. for instance, if the question asked “why was there a plateau in the cooling curve of naphthalene?”, it is not sufficient to answer it with “the plateau characterizes the freezing/melting point of naphthalene”. what happens when the freezing point is reached? why does temperature remain constant at that point?

7) references

• please cite your references properly. in the event that you did not use any reference for your answers and/or discussion, please indicate at the end of your formal report that you did not use any reference.

regarding the format of the postlab, i would require everyone to follow the format suggested by the syllabus that i gave out early this semester EXCEPT the part where the syllabus asks you to integrate your answers to questions to your discussion part. please DO NOT integrate your answers to the questions to the discussion part of the experiment; allot a whole new part for the answers to the questions. on the other hand, the executive summary or abstract should provide the reader with a quick glance at the important concepts involved in the experiment and the pertinent results that was obtained in the activity. it should be short and concise.

that would be it for now. if you have any questions, comments or concerns, please do not hesitate to email me (i believe that my smart sim had already so i doubt that anybody could reach me there).

thank you very much and God bless you all!