# key - Describe the main difference between the beads used...

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1. Describe the main difference between the beads used in ion exchange chromatography and those used in size exclusion chromatography. Beads for IEC rely on a charged chemical that is covalently bound to the beads in order to separate your molecule of interest away from the others. For SEC, the beads themselves cause the separation to occur, so no additional chemicals are necessary on the beads. 2. You have a stock solution of 4M NaOH (molecular weight = 40.0). You put 10 μ L of this stock in 190 μ L water, and then put 10 μ L of the resulting solution in 990 μ L water. Finally, you take 25 μ L of this last mix into 475 μ L water. What is the final molarity of this last solution in micromolar ( μ M)? (Show all calculations for full credit, and keep it neat! Work on the scratch page if necessary.) 100 μ M 3. You have a stock solution of 3.8 M NaCl (MW = 58.44 g/mol) and want to make 200 mL of a 0.2 M solution. How much of the NaCl stock and how much water should you mix? Show all calculations for full credit, and keep it neat. 10.5 ml NaCl + 189.5 ml water 4. A molecule has an extinction coefficient ε of 1.80 for a 1% solution, and has a molecular weight of 222 g/mol.

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