In preparation for a protein purification experiment, you have been asked to prepare 100 mL of an aqueous solution of Tween20. The solution should have a final concentration of 4.25% (v/v) Tween 20. There is a bottle of Tween 20 (100% v/v) on the lab shelf. Describe the method that you will use to prepare the solution.
To answer this problem, you need to understand the concept of expressing concentration as a percentage. In this case, the desired concentration is expressed as "% (v/v)", where the "v/v" means "volume of solute / total volume".
The official formula for calculating the volume percent is :
Volume percent = (volume of solute) / (volume of solution) ) x 100%
What is a solute? A solute is the "substance" that makes up your solution. The solute is dissolved in or mixed into a solvent to create a solution. In this case, the "solute" is a detergent called Tween 20, and the solvent is water.
Watchpoint: A COMMON MISTAKE made by ...
The solutions applies volume percent and solution chemistry to calculate the volume of solute needed to prepare a laboratory solution