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bfesser
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Hypothetical Chemist
Ok, just for fun, I'm going to pose a hypothetical puzzle of sorts that I thought up this morning, in order to see if you guys/gals come up with the
same set of solutions that I did (pun intended):
<strong>Scenario:</strong><hr />You are seated at a glass table. Two clean empty 500 mL Kimax beakers are placed side by side in
front of you. A lab technician proceeds to pour, from an unmarked PTFE bottle, ca. 300 mL of a clear colorlous liquid into the beaker on your
left<!--HCl-->. She then pours ca. 300 mL of a clear colorless liquid from an identical bottle into the beaker on your right<!--NaOH-->.
You are told that one of the bottles contains 1 M HCl (<em>aq.</em> and
the other contains 1 M NaOH (<em>aq.</em>. You are provided a 10 cm
length of plain borosilicate glass tubing with a circular cross-section (average diameter/bore, not capillary), flame-polished on both ends, to do
with as you please. You are asked to determine which beaker contains which solution.<hr />
<strong>Constraints:</strong>
-You are not allowed to move the beakers.
-You are neither provided nor allowed any other chemicals, reagents, equipment, instrumentation, etc. other than that outlined above.
-For the purposes of this hypothetical scenario, your olfactory senses have been nullified (perhaps you were huffing H<sub>2</sub>S?). No
taste/smell.
-You are not permitted to apply solution to your corneas in order to determine which does the most damage (sorry).<!---dissolving hair
+slippery vs. 'rubby'
+evaporation residue
-drink contents
-'bead'
+/-optical refraction
+adherence to glass
-viscosity
+bubbling carbon dioxide
-ask the technician which is which
-dissolve a hair-->
<strong>Notes:</strong>
-The scenario and constraints may be subject to slight alteration, as I was away from the computer when I thought of all this, and I may have
forgotten something.
-No cheating! Use your existing knowledge... please don't use search engines.
[Edited on 3/2/13 by bfesser]
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Mailinmypocket
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Dip one end of the glass tube into one beaker, dip the other end into the other beaker. Let it dry and remember which side is which, the side with a
residue will be the NaOH (converted to carbonate in contact with air) and the side that dries with nothing at all the HCl?
Unless I am missing something, I would try that first! If there is no time to watch water evaporate(fun!), then I'm not sure :S
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bfesser
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Good. That's one of the solutions (the simplest). Any more?
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DraconicAcid
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That's a better solution that the one I thought of- dip the rod in solution, then run the rod through my fingers to see if it makes my skin feel
soapy.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Simbani
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You could just wait as long till one beaker got dissolved by the NaOH..
Nah, second way I would go is to get one drop out of both solutions and place it on the glass table. To one drop on the table you now add a drop of
the other solution. As expected you get a neutralisation, but you don´t know which beaker contains what chemical. So take your rod and blow air with
you mouth in both beakers for like 5 minutes and now take a drop from both solutions and place them on the table.
You previously reacted the NaOH with the CO2 in your lungs to NaCO3 or NaHCO3. So now you´ll have to wait till both drops are evaporated, and the
drop which leaves a residude was from the beaker containing NaOH-solution.
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Mailinmypocket
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Just out of curiosity; why the neutralization step?. If you prefer to place a drop on the glass table why not just put a drop of each and blow on them
instead? The same carbonate residue would appear, without needing to bubble air though a whole beaker of solution.
<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: removed
unnecessary quoting]
[Edited on 7/9/13 by bfesser]
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Endimion17
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1) I'd put one drop to my tongue and give it a taste. It will sting a bit, but hey, corneas are forbidden, tongues are not. 
2) Smearing few drops of the solution between my fingers. NaOH will be more slippery.
3) This might not work, but it's worth a try. Equimolar solutions f NaOH and HCl at exact temperatures have slightly different densities. NaOH is 1.04
g/cm3, and HCl is 1.017 g/cm3 @25 °C, but the numbers are not important, the difference is.
I don't know if it would work with 1 M solutions because that's quite dilluted, but one could try picking up some of the solution A with th tubing and
then drip it into the second beaker while observing how light bends. If the bending "blob" sinks, the drop is NaOH and if it kind of floats, it's HCl.
I've never tried it, but it should work with high enough concentrations. 1 M might not be enough, but hey...
4) NaOH should wet the glass more than HCl, but that might not be visible enough for 1 M. So, I don't know.
5) If you snap the tubing and then score itself with the snapped piece to make a fine, dusty mark. Then you let each scored piece sit in its solution
for a day. Unlike 1 M HCl, 1 M NaOH might do something about the score, but I really don't know for sure.
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kuro96inlaila
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As for me,I would exhale into the tubing carefully to not let the atmospheric air reenter the tube and place my thumb on one of the hole.
Then I would dip the the tubing into the solution.Which is NaOH solution will rise noticeably in the tubing.
And of course I'd re-exhale into the tubing if the is no reaction on the first solution.
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elementcollector1
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Smell them. HCl will be very distinctly different from NaOH
And again, pour some on a finger of both of your hands to see which one turns your skin soapy.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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plante1999
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I am waiting for AJKOER answer! It should be pretty funny, I would do like Mailinmypocket.
I never asked for this.
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Mailinmypocket
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Hmm... Given that no additional reagents are allowed, no bleach could be used to generate chlorine gas from the HCl beaker...
<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: removed
unnecessary quoting]
[Edited on 7/9/13 by bfesser]
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plante1999
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Sad for him! I'm sure he would love to do hypothetical chemistry challenge given he do not do real chemistry.
<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: removed
unnecessary quoting]
[Edited on 7/9/13 by bfesser]
I never asked for this.
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bfesser
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<strong>DraconicAcid</strong>, well done. My initial solution was to simply dip an index finger in each solution, and then rub together
with thumb. The slippery one indicates the NaOH. The glass tube was not necessary for this test.
<strong>Simbani</strong>, there would not be enough NaOH in the solution to dissolve through the beaker. Nice try, though. You were on
the right track with exhaling CO<sub>2</sub> into the solutions.
<strong>Endimion17</strong>, tasting was disallowed, remember? For the sake of simplicity, 'stinging' counts as a taste, not a damaging
effect on the cells/nerves of the tongue, or whatever actually causes it. As for adding one solution to the other dropwise and observing the
refraction caused by concentration gradients, they will react to form NaCl(<em>aq.</em>. I thought of this, but am not exactly sure it would work. Perhaps someone could actually perform this experiment (1
M solutions!) and record a video for us. I also came up with the glass wetting solution—quite elegant, nice work! I did think of trying to
powder the glass by grinding on the table, but did not think of snapping the tube and using the break to score the other piece. That should work.
Wonderful.
<strong>kuro96inlaila</strong>, I did not think of your idea. I'm not sure it would work, but it's another elegant solution. Nice work.
<strong>elementcollector1</strong>, smelling is disallowed. 'Soapiness' already repeatedly suggested. Did you <a
href="http://en.wiktionary.org/wiki/TL;DR#English" target="_blank">TL;DR</a> <img src="../scipics/_wiki.png" />?
<strong>plante1999</strong>; hilarious! Perhaps for humor's sake, we'll allow AJKOER any hypothetical chlorine reagents he desires.
<strong>UPDATE:</strong>
There are four more solutions on my mental list that haven't been suggested yet. Keep them coming. You've got five of my ten, plus one I didn't
think of.
Since suitable answers have been given, in my mental hypothetical, the beaker on the left contained HCl, and that on the right, NaOH—not
that it matters.
[Edited on 7/9/13 by bfesser]
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elementcollector1
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Ahaha... maybe?
<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: removed
unnecessary quoting]
[Edited on 7/9/13 by bfesser]
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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bfesser
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<strong>Progress (in no particular order):</strong><ol><li>soapy feel on skin (NaOH)</li><li>evaporation residue
(NaOH/Na<sub>2</sub>CO<sub>3</sub></li><li>adherence to glass (wetting)</li><li>exhaling into solution (several variants)</li><li>refraction of
light (Endimion17's suggestion was close enough)</li><li><!--dissolve hair-->???</li><li><!--drink
one-->???</li><li><!--'bead'-->???</li><li><!--viscosity-->???</li><li><!--ask
technician-->???</li><li type="circle">vertical displacement by CO<sub>2</sub> absorbtion (nice one,
kuro96inlaila!)</sub></ol>
[Edited on 3/2/13 by bfesser]
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woelen
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When I post this, I read no other responses. Given the constraints I would do the following.
Dip the pointing finger of my right hand in one beaker and the pointing finger of my left hand in the other beaker. Then with my thumb I slide over my
wet finger. The one, which feels slippery is the 1 M NaOH, the other then must be the HCl. After this exercise I would quickly wipe off the slippery
finger on my clothes. The damage of 1 M NaOH done to my skin is very small, especially if the situation holds for just a few tens of seconds.
The knowledge I use is that at 1 M concentration, NaOH already makes the skin feel slippery.
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Diablo
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If your skin is greasy rub some in two spots on the table. Add a drop of a different solution to each. The one that turns soapy is NaOH.
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Diablo
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Also if you have curly hair put some in each beaker the one with lye will straighten it some.
[Edited on 3-2-2013 by Diablo]
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woelen
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Solution 6: Pee a little on the table and allow the urine to get old and stale for a while (keep it warm for best results ) in order to get some ammonia. Then take a drop of liquid from both beakers and
keep that above the old pee with the ammonia smell. The HCl will give off faint smoke, the NaOH does not. The reaction will not be strong with 1 M
HCl, but one definately can see faint smoke of NH4Cl.
[Edited on 2-3-13 by woelen]
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kavu
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I thought that saliva behaves differently in the two solutions but I had to cheat and do the experiment. Indeed in NaOH the bubbles break down faster
and the salliva tends to collect to the sides of the beaker. Live and learn...
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Diablo
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You could urinate into both solutions, the one with lye will convert the urea to ammonia.
Woelen's gave me the idea for this one
[Edited on 3-2-2013 by Diablo]
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bfesser
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<strong>Diablo</strong>, you essentially guessed number six on my list. I often catch myself pulling out my hair while doing chemistry...
though not for this reason!
<strong>woelen</strong>, I must admit, the thought of using urine crossed my mind. I didn't think it was worthy of inclusion into my list
of ten, as the results may be hard to judge. I guess I should have included it. Let's make that number 11. Nice work. Perhaps you'll be willing to
try this one and post it on your site?
<strong>Progress (in no particular order):</strong><ol><li>soapy feel on skin (NaOH)</li><li>evaporation residue
(NaOH/Na<sub>2</sub>CO<sub>3</sub></li><li>adherence to glass (wetting)</li><li>exhaling into solution (several variants)</li><li>refraction of
light (Endimion17's suggestion was close enough)</li><li>dissolve hair (Diablo suggests NaOH straightening curly
hair)</li><li><!--drink
one-->???</li><li><!--'bead'-->???</li><li><!--viscosity-->???</li><li><!--ask
technician-->???</li><li>urinate on table/in beakers (leave it to woelen...)</li><li type="circle">vertical displacement by
CO<sub>2</sub> absorbtion (nice one, kuro96inlaila!)</sub></ol>
Four to go! Overall, I'm very impressed by the creativity and resourcefulness of some of these answers! If you blokes enjoy this, maybe I'll try to
think of other puzzles like this.
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Diablo
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Break the glass tube and give yourself a small cut. Put some blood on one part of each half tube and dip in the solutions, the one with lye should
make it change color/texture.
[Edited on 3-2-2013 by Diablo]
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kavu
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Well this is a bit far fetched but you could knock out two teeth and place those into the solutions and wait for the other one to dissolve 
EDIT: Well you could do it with only a one tooth as well..
[Edited on 2-3-2013 by kavu]
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Diablo
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You could place part of a nail in each solution, the one with lye will soften it.
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