8.4 Practice problems

  1. What volume of 2 M NaCl would you need to prepare 400 ml of a 0.3 M solution?
  2. What volume of 2 M NaCl would you need to prepare 100 μl of an 800 mM solution?
  3. What is the final concentration of a solution where 50 µl of a 0.5 M solution is added to 825 µl?
  4. To make 100 ml of a 0.1 M solution of HCl how much concentrated HCL do you need? (Concentrated HCL is 11.6 M.)
  5. If you have 250 ml of 1.25 M NaCl, how many ml of 0.25 M NaCl can you make?
  6. You boil a 450 ml solution of 0.2 M KCl until the volume is 225 ml. What is the final concentration of KCl?
  7. What is the dilution factor when 0.25 ml of aqueous solution is added to 38.75 ml of water?
  8. You have 2 l of 0.25 M Na2CO3. What volume is required to make 100 ml of 0.1 M Na2CO3?
  9. You have a BSA solution at 10 mg ml1. You remove an aliquot of 50 µl and mix it with 350 µl of water. You then remove 25 µl of this dilution and add it to 1.25 ml of water. What is the BSA concentration of this solution? Give your answer in µg ml1.
  10. You are making a PCR reaction with a final volume of 50 µl. How much 10x PCR buffer do you need to add to the reaction? (Hint: assume the final concentration should be 1x)
  11. How much water must you add to a 1 ml protein sample with a concentration of 0.5 µg ml1 to bring about a 10-fold dilution?
  12. In performing a blood test for a crucial analyte, you dilute 100 µl of plasma with 300 µl of distilled water. The test still reads as needing further dilution as it is outside the range of your standard curve. You then take 100 µl of the first dilution and add 300 µl of distilled water. What number to you need to multiply your result by to determine the concentration of the analyte in the plasma?
  13. You purify DNA from E. coli and obtain 100 µl of DNA at 0.75 mg ml1. You want to amplify a fragment of DNA by PCR. You need to add 50 pg of plasmid DNA to your PCR reaction.
    1. How much of the original solution do you need to add?
    2. Is this practical given the minimum volume you can accurately pipette is 1 µl?
    3. Work out a serial dilution scheme using 1 ml tubes. Your PCR reaction volume is 25 µl and we want to keep the added DNA to 10% or below of the total volume.

Solution to Practice Problem 8.3.


Solution to Practice Problem 8.6.


Solution to Practice Problem 8.9.


Solution to Practice Problem 8.10.


Solution to Practice Problem 8.13c.

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