Chromatography Sumnary Questions

Chromatography Sumnary Questions David Fan Mr. Chesbro P-2 1. Who did it?

Emily Volz did 2. What must be true about the pen belonging to the criminal? What do we call these types of pens, and why?

The pen contains only one type of ink that is insoluble in water. We call these pens permanent markers because they have water insoluble ink.

3. While you have been busy solving your crime I have been running an experiment of my own. I placed a dot from the criminal’s pen on a sheet of chromatography paper and placed it in a beaker of liquid. The chromatogram created is different from yours, and yet it is the same pen. Does this mean that the criminal is actually innocent? Explain why the chromatogram is different from yours.

No. It just means that you used a different solvent. The pen that the criminal used was insoluble in water, but it’d be soluble in ethanol. So, chromatograms are the same only if you use the same pen on the same type of paper, in the same solvent.

4. Write a paragraph explaining how you solved the crime, and use the following terms: chromatogram, chromatography, solutes, higher solubility, lower solubility, inks, solvent To determine the criminal, I realized that I would have to compare the two chromatograms using paper chromatography and see which ink samples have the same composition. Paper chromatography works because the inks of most pens contain many water soluble solutes which can be separated when placed in water. After dipping the samples in a solvent of water for 4 minutes, I found that samples B and D had separated into their various solutes, forming a pleasant smear. But samples A and C looked the same. Neither of them had separated.

So, I concluded that the ink from sample C must come from the same pen as sample A. In terms of solubility, both Sample B and D had a higher solubility than Sample A because they rose much higher. Sample D had a lower solubility than Sample B.