C106 Colorimetric Determination of Concentration Pre-Lab to these in a new Word

Question

C106 Colorimetric Determination of Concentration Pre-Lab to these in a new Word document. Include a heading with your name, date, and section number at the top of the page. number. Save your document as a PDF and upload to Blackboard in the Pre-lab assignment area for this experiment. Number your answers with the corresponding question Explain how the concentration of a colored solution can be determined by shining a beam of light through it (in evaluating your answer, we're looking to see that you have a reasonable grasp of the overall theory of this experiment). The colorimeters you will use in this experiment are capable of measuring the absorbance of a solution at four different wavelengths of light. Explain how you will determine which 1. 2. wavelength you will set yours to before you measure the absorbances of your solutions Your experiment will require you to make four standard solutions, each to a different concentration of Allura Red AC. Describe how you will make these. 3. 4. Refer to the Beer's Law Plot in the Background. What absorbance would a solution with a concentration of 0.0037 M have? What concentration would a solution with an absorbance of 0.25 have? You are instructed to deliver "7 ml" of liquid from a burette. How many ml can you actually dispense and to what decimal place should you take your burette readings? (If you have no idea, see the document "Lab Techniques" on the c 5. webpage.) English (US)

Explanation / Answer

1) Absorbance in important factor in determining concentration of colored solution by using colorimetry. As colorimeter measures the intensity of color and light transmittance by the sample to acheive the concentration. As colorimeter can use only one wavelength and works in visible range only. When beam of light passes through colored solution, the amount of light absorbed depends on the nature of molecule absorbing the light, their concentration and thickness of the solution.

2) As Allura Red AC is red in color. Generally observed color is complimentry to the color of light absorbed. And the complimentry color of Allura Red AC is green, so the wavelngth selected for this experiment is 480-560 nm. Wavelength of red color 640-700 nm are not absorbed but transmitted, and give perception of red color.

3) Firstly prepare stock solution of Allura Red AC in available 500ml or 1000ml standard flask. Molarity used for Allura Red AC is 1.90 X 10-4 M. So just weigh on the balance and make standard stock solution. Then take four 100 ml volumetric flask. NOw add 5ml, 10 ml, 15 ml and 20 ml of stock solution into the volumetric flask and make the volume upton 100ml. Your standard solution are prepared.

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