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Help with surfactant lab

I have to determine the foaminess and different characteristics of a surfactant solution and this is the procedure:

  1. Create surfactant solutions raging from 0.0% to 2.0% (students will decide exact percentages)
  2. QS Water
  3. Shake solutions in graduated cylinder to create foam - establish a method, this method should be reproducible and needs to be reported in the lab report
  4. Determine foam stability over 5-10 minutes (foam volume vs time) - the details will be determined by your method you have established. There is no wrong answer. HINT: you need at least 3 points to determine any type of trends

my question is. What does step 1 mean? Is that the concentration of the solution? What do they mean by loading ladder?  

One of the students in my class I did loading levels of 1,1.5 and 2% at 100 gram solution and I don’t understand if that is the concentration of the solution but then it doesn’t make sense to me. How can a 2%solution have a 100 g of surfactant that would mean I would have to add more than 4L of water. Please someone help! 

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Contributor III

Re: Help with surfactant lab

Dear Sabrina,

First, (I am also a chemistry teacher) whenever you have any questions about an assignment, ASK your teacher/instructor!  They are usually more available, and know what THEY expect to see in a proper answer.  Good ones are always ready to help to clarify a procedure.

Second, don't get to caught up with what the others are doing.  Stick with the facts of the procedure.  The first statement is to make a series of solutions in a certain range of concentrations. That's it!  HOW you make those solutions is up to you, and there are NO specific requirements on the amounts of materials.  In general practice it is good to use the minimum amounts necessary for accurate measurements.

I didn't see any mention of a "loading ladder" in the procedure.  It sounds like someone else's process for making a series of solutions, so it doesn't really matter, as long as you create the required series of solutions with different concentrations of the surfactant in water.  You may also be confusing the 100grams of solution with the surfactant.  Roughly 100mL of water is 100g.  So you can make up 0.5, 1.0, and 2.0% solutions each in a total volume of just 100mL.  Maybe you also meant "loading level" (the amount of surfactant added to the water) instead of "loading ladder".

Happy learning!


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