Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Osbourne_Cox on October 06, 2009, 09:11:46 PM
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In my lab today, I was confronted with the following question:
If K= C ether/C water, is the value of K in part A (I will explain in a second) large or small or ~1.0 for methylene blue and also methyl red?
In part A, water, ether and methylene blue were placed in a test tube, and the methylene blue went straight to the bottom layer containing the water. In a separate test tube, water, ether and methyl red were added, and the methyl red stayed in the top layer, the ether.
This question is confusing to me, and I'm not sure what the answer would be and why.
Thank you.
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k is an equilibrium constant (think gen chem). C is concentration of the solute in the given solvent.
Thus, the equilibrium constant (K) is equal to the concentration of the solute dissolved in ether over the concentration of the solute dissolved in water.
Does that help?
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Yes, now I understand the equation. What solute did I use though? I don't know how to relate it to the dyes. Are they asking if a solute was added, what would the K outcome be, or do the dyes count as solutes?
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the dyes are the solutes and you partitioned them between ether and water. The color of the layers tells you the relative concentrations of the dyes in the two layers.
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How does that work? In the manual they were both 0.006M. ???
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I suppose 0.006M is the initial concentration, but once you add them to mix of water and ether. Then dyes 'moved' to the liquid in which they 'felt better' - so their concentrations changed (although - due to the mass conservation - total amount of dye have not changed). Just looking at the color difference between layers you should be able to tell which layer contains now higher concentration of the dye.
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One layer is red and one is blue. When you say colour difference, are you referring to the difference in colour, as in red vs blue, or the difference in colour intensity of the dyes in separate mixes before being mixed together?
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One layer is red and one is blue. When you say colour difference, are you referring to the difference in colour, as in red vs blue, or the difference in colour intensity of the dyes in separate mixes before being mixed together?
They are in separate test tubes right?
1) What layer is the methylene blue soluble in? Is the water layer really blue or just a little blue? Is the the ether blue? If one of the layers is darker blue in color than the other layer, what does that tell you about the methylene blue?
2)What layer is the methyl red soluble in? Is the ether layer a little red or dark red? Does the water layer have any red color? If one of the layers is darker red in color than the other layer what does that imply?