The mass balance equation is C1 x V1 = C2 x V2, where


      V1 and V2 are related since V2 = V1 + dH20


      Common units


      Miscellaneous questions on the mass balance equation


  1. Complete the table below.

Stock Concentration


Vol. Of Stock Used


Desired Concentration


Desired Volume


Vol. Of Water Needed for Dilution



20 mL

100 mM

100 mL

80 mL

20 mM



10 mL


400 M



30 mL



40 mL















  1. You are given 50 mL of a NaCl stock solution of 100mM, and you need to make up a dilution series for an experiment. These dilutions are 10mM, 20 mM and 40 mM. Construct a dilution table if the final volume of each dilution is to be 35 mL Would you have enough stock solution to make up all these dilutions?


  1. If you were given 100mL of 20uM of Riboflavin solution, and you would like to make up a dilution of 15 M of total volume 20 mL, how much distilled water is required?


  1. You are in the process of making up a dilution but you have forgotten to write down the concentration of the stock solution that you used. You know that you used 50 mL of distilled water for your dilution, and that your final volume was 95mL. If the concentration of the dilution was 300 mM, what was the concentration of the original solution?


  1. You are given 10 mL of 2 M of catalase enzyme stock solution, and you need 60ml of catalase enzyme at a concentration of 200M for an experiment. How much distilled water is necessary to make up the required enzyme concentration?


  1. Nancy has 2 L of 3 M stock solution of Riboflavin for an experiment. She has only 200 mL of distilled water available for a dilution. What would be the concentration if she uses all of the stock and water?


  1. 300 ml of buffer was added to 1L of 40mM of catalase enzyme. What is the final concentration?


  1. An experiment is being run using 2M KCl. There was 1L of stock at the beginning of the experiment, and there is only 150 mL remaining. Further, there was 480mL of distilled water at the start and there remains 30mL. Assume all the stock and the water were used to make up a dilution. What would be the final volume of the dilution? What would be the final concentration?


Solutions to Problems