Chemistry labs?

Student Lounge College Life
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<p>HikoSeijuro: I'm attempting to decide whetere your posts are from pure naivete and ignorance or that you're intentionally aggravating CCers.</p>

<p>I took general chemistry in college during my senior year in high school, and my labs were once a week for about 4 hours. </p>

<p>You do the pre-lab (read it, set up what you want to do, get an idea for how it's going to run and you're going to work quickly, efficiently, and effectively) and when you arrive at your lab time, materials are laid out. Using your pre-lab, you use the items (chemicals, special equipment, etc) you need (students had their own beakers, erlenmeyer's flasks, burets, stirring rods, thermometer, scapula, magnetic stirrer, etc. to use already). You use your pre-lab to help you set up your experiment and run the experiment. TA's and/or the professor were there to help you, but not do the experiment for you. Most of the time, the TA or professor would ignore you if the answer was in your pre-lab.</p>

<p>Experiments differ widely. Some have 6 or more experiments you'll have to run and finish before the lab time ends, some have a few. They're designed to reinforce the material you covered during lecture and help substantially in understanding the material. My labs definitely helped me understand the material and helped on the mid-term and final as I could use concepts learned during those labs and apply it to theory.</p>

<p>After the lab, you're expected to clean up. There was a hazardous waste bin where you there heavy metals and other toxic chemicals away and most everythng else could be disposed down the sink. As long as you're careful and keep the water running, there should be no danger. I didn't use gloves (because chemicals can get caught under the glove), but always wore by lab googles. You won't die while working on labs, short of drinking hydrochloric acid or dunking your head in 12 M ammonia. It's not that hard cleaning up after yourself. And the next person using the lab greatly appreciates it.</p>

<p>I had a lab final in the class (which accounted for about 50% of our total grade on the final) where we were given "unknown" compounds and we had to determine the compounds through experiments we designed ourselves. (this is called qualitative analysis).</p>

<p>Labs are graded, at least where I took it, by your lab report. The quality of your lab report often reflects how much effort and time you put it. I spent about 3-4 hours outside of the lab writing the lab reports (they took forever to do...calculations everywhere). Dependent on your professor, lab reports counted for 1/3 of my grade.</p>

<p>That was just for general chem. PChem is hard (from speaking to students and reading their lab experiement, as well as material covered). Quantative Analysis classes have labs that didn't have lab reports, but you were based on accuracy. For example, if the experiment you were doing needed to yield at least 95% of a certain compound, however close you were to that yield rate would be your grade.</p>

<p>And why don't professor's just give data and you write on them? Because you won't understand how and why the data came from; this makes writing the lab report difficult if you don't understand how the data was derived.</p>

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<p>There are not maids in college...in chem labs or in dorms. You are your own responsibility.</p>

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<p>Re safety: all labs have eye wash and shower stations to use if an accident should occur. Some labs have ventilated hoods with safety glass between you and your experiment. Of course, goggles are mandatory.</p>

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<p>
[quote]
Never washed dishes before. The danger comes from the chemicals.

[/quote]
</p>

<p>Newsflash: food is acidic or basic. And guess what - food is a collection of chemicals.</p>

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<p>hiko, you are one bored d.u.m.b.a.s.s.</p>

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<p>


</p>

<p>haha...call him the forum d.u.m.b.a.s.s.</p>

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<p>So, how do you do a qualitative analysis?</p>

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<p>Oiram, I take it that the question is addressed to me, and not the OP.</p>

<p>An example of qualitative analysis would be that you're given 10 different elements to study and you perform procedures to separate them from their compounds to confirm their presence. For example, a simple identification would be the confrimation from lead. You're given a solution containing a combination of silver (I), mercury (II), and/or lead (II) or all of them. From previous experience, you understand that these cations can precipitate with chloride. So you add HCl which results in the precipitation of these compounds. Now you have precipitate of these compounds in your precipitate. Again, drawing from chemistry knowledge, you would know that if there were any PbCl2 in the solution (originally Pb), PbCl2 could be dissolved with hot water (though solubility for chlorides is always quite low. But PbCl2 has a higher solubility rate compared to Hg2Cl2 and AgCl). But dissolving the PbCl2 into a solution, you now can centrifuge the mixture of precipitate and PbCl2 solution and separate the two. To test for lead, in that solution, you would add acetic acid to break down the PbCl2 compound (if any), and then add potassium chromate to the solution. As potassium chromate is highly soluble, (most Group I elements are), the chromate will form a compound with the lead (II) and form lead chromate. Since this test is only good for lead (when compared to silver and mercury), if a yellow precipitate forms (characteristic of chromate compounds), then you know that lead is present (as lead is the only one which would form a precipitate given that Cl- and Pb2+ have been dissociated by the acetic acid). And that's one of ten experiments in terms of qualitative analysis. And your grade is based on precision. How many elements you identify.</p>

<p>You conduct all those experiments from previous experience in other labs and of course the lecture. Using your knowledge of chemistry and experience in previous labs, qualitative analysis can be really fun and easy.</p>

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<p>Thank for the very descriptive post, eiffelguy87. Doing that seems like you are kinda placing the pieces of a puzzle together.</p>

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<p>My chem teacher in high school told me that we might have to do something like that. It looks like it could be fun but it also looks like it could be frustrating.</p>

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<p>Yeah, it took two lab periods (about 6-8 hours) to test all 10 elements. But is can be really fun because precitates can be colored (like a rosy nickel precipitate) and so can solutions (like a dark blue cobalt solution).</p>

<p>But then it can get plain nasty when you're trying to separate compounds from sulfur.</p>