You have a stock solution of 1.0% m/v concentration and you wish to use it to prepare 50.0 mL of a 0.25% solution. Explain the calculations involved in performing this dilution.
-what is the starting volume and concentration?
-what is the starting volume and concentration?
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My general method is, if you have to dilute x% stock to y%, then take y mL of stock
and make it up with diluent to a total volume of x mL. Then if you are preparing a
certain volume, V, by simple proportion, the amount of stock required is (V*y/x) mL.
To dilute 1.0% to 0.25%,
take 0.25 mL of stock and make up to a total volume of 1.0 mL.
You require 50.0 mL, so volume of stock = 50.0*0.25/1.0 = 12.5 mL,
and you make this up to 50.0 mL by adding 37.5 mL of diluent.
Check that final concentration is correct : 12.5 mL * 1.0% / 50 mL = 0.25%.
and make it up with diluent to a total volume of x mL. Then if you are preparing a
certain volume, V, by simple proportion, the amount of stock required is (V*y/x) mL.
To dilute 1.0% to 0.25%,
take 0.25 mL of stock and make up to a total volume of 1.0 mL.
You require 50.0 mL, so volume of stock = 50.0*0.25/1.0 = 12.5 mL,
and you make this up to 50.0 mL by adding 37.5 mL of diluent.
Check that final concentration is correct : 12.5 mL * 1.0% / 50 mL = 0.25%.