THE MASS BALANCE EQUATION
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The
mass balance equation is C1 x V1 = C2 x V2, where
 C1 is the concentration of the stock solution
used
 V1 is the volume of the stock solution used
 C2 is the desired concentration or the
concentration of the required dilution
 V2 is the volume of the dilution or the final
volume of the solution
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V1 and V2 are related
since V2 = V1 + dH_{2}0
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Common units
 concentration: molar (M, g mol.wt./L),
percentage (%)
 volume: liters (L)
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Miscellaneous questions
on the mass balance equation
 Complete the table below.
Stock Concentration
(C1)

Vol. Of Stock Used
(V1)

Desired Concentration
(C2)

Desired Volume
(V2)

Vol. Of Water Needed for Dilution
(dH_{2}O)


20 mL

100 mM

100 mL

80 mL

20 mM


10mM

10 mL


400 µM

10mL


30 mL


100µM

40 mL



15mL



30µM

50mL

20mL






 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?
 If you were given 100mL of 20uM of Riboflavin solution,
and you would like to make up a dilution of 15 µM of total volume 20 mL,
how much distilled water is required?
 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?
 You are given 10 mL of 2 M of catalase enzyme
stock solution, and you need 60ml of catalase enzyme at a concentration of
200µM for an experiment. How much
distilled water is necessary to make up the required enzyme concentration?
 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?
 300 ml of buffer was added to 1L of 40mM of
catalase enzyme. What is the final
concentration?
 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