Preparing a % w/v Solution

The % w/v is the number of grams in 100 cm3 of SOLUTION.

You prepare a % w/v solution by dissolving the component in a small
amount of solvent and THEN making up the final volume of the solution
TO THE REQUIRED VOLUME.




To prepare 100 ml of a 5 % w/v solution of Dextrose:
Find out how much Dextrose you need.
100 ml of solution needs to contain 5 grams of Dextrose.
Weigh out 5 grams of Dextrose.
Dissolve the Dextrose in a small amount of water.
Make up the volume of the solution to 100 ml with water.


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Mixing Ethanol and Water

The dissolution of Ethanol in water is:
  1. an exothermic reaction
  2. accompanied by a significant contraction in the total volume.

The heat produced during the exothermic reaction will affect the volume of the solution.

Preparing a solution of Ethanol in water
After you have mixed the Ethanol and water together, you must:
  1. wait for the solution to cool to room temperature
  2. wait for the solution to finish contracting.
When both of these have occurred, you can top up the solution to the volume required. You should then check that the temperature and volume remain the same.
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