Dilutions and Spectrophotometry Problems with Answers

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Question 1

If you wanted to make a 0.4 M NaCl solution and you wanted a full Liter of it, how would you make it?

Question 2

Now suppose you wanted to dilute this 0.4 M NaCl solution by a 1:10 dilution – how would you do this?

Question 3

Suppose you wanted a 2:25 dilution of a stock solution, but you wanted 200 mL of it. How would you make this? What if you only wanted 10 mL of it – how would you make this solution?

Question 4

Use the following data to prepare a standard curve. Attach the curve to this assignment.

1

A. What would be the absorbance of a solution with a concentration of 4.0 ug/mL? What is the concentration of a solution with an absorbance of 0.75?

B. Now, suppose you had an unknown sample that had been diluted as follows: 1 mL of unknown + 4 mL of solvent. This diluted sample was then tested and had an absorbance of 1.0. What is the concentration of the original solution? Show all of your work to determine this.

C. Finally, suppose you had an unknown sample with an absorbance of 3.2. Could you determine its concentration directly from the standard curve? Why or why not?