5. If you perform a 1:4 dilution on 50 mM Tris base, what is the final concentra

Question

5. If you perform a 1:4 dilution on 50 mM Tris base, what is the final concentration? 6. A student diluted 1ml of a stock solution (1M) of a compound with 9 ml of water Then took 1ml from that solution and diluted with another 9ml of water. Then took 10ml of the resultant solution and added 90ml of water. What is the final concentration of the soluti on? 7. Is the extinction coefficient for a molecule the same for all wavelengths? 8. After obtaining calibration curve for your k intercept of 0.01, you determine that your unknown has Absorbance of 0.2. Is it enough to determine the concentration of your unknown and how? nown solution to have slope of 2.5 and 4. You prepare several dilutions of an unknown compound. You measure the absorbance of each solution at 340 nm using a 1 cm cuvette (your results are listed in the table below). What is the extinction coefficient in (M.cm)-1) of the compound? (Hint: assume that each of the individual values contains some degree of experimental error.) Concentration (M) Absorbance at 340 nm 0.009 0.020 0.061 32 0.189 Page 7

Explanation / Answer

#6. Apply concentration eqaution on every situation i.e .

M1V1 = M2V2

In first dilution , 1M × 1ml = M2 × 10ml

Then M2 = 0.1M

Similarly on second Dilution , 0.1M × 1ml = M3 × 10 ml

M3 = 0.01 M

And then in case of third dilution ,

0.01M × 10ml = M4 × 100ml

M4 = 0.0001M , hence this is the final concentration .

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