Spectroscopy Mixture 1 Post-Lab

Spectroscopy Mixture 1 Post-Lab - Q# Question Text 4) Part...

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Q# Question Text 4) Part I. Free Response 2 points. Why do we allow electronic instruments to warm-up before use? Your Answer: A lot of electronics need to boot-up before use because it helps them run more properly and a lot smoother. Specifically for the spectrophotometer you don't want the temperature difference that happens within the machine in the first 10 minutes to effect any of your calculations. The warm up time also helps the machine calibrate and initialize. Text Answers to be Scored by your TA 5) Part I. Free Response 2 points. Why is it important not to have fingerprints on the cuvette? Your Answer: A spectrometer sends light through a sample (inside the cuvette) and detects how much of this light is absorbed by the sample.If you get fingerprints on the cuvette, this could intefere with the light absorbtion, and therefore your readings would be off. Text Answers to be Scored by your TA 6) Part I. Free Response 2 points. Why is it important to align the cuvette in the sample holder the same way each time? Your Answer: It is important to align the cuvette in the sample holder the same way each time because the wall thicknesses/clarity of different sides may be different. This might affect the intensity of the light passing through the sample which would also affect your results. Text Answers to be Scored by your TA 7) Part I. Data Entry No Scoring. In Part I you prepared the standard solutions of BROMOTHYMOL BLUE. Please enter the precise concentration of the undiluted stock solution #1 of the BROMOTHYMOL BLUE in micromoles per liter. (This is your most concentrated (undiluted) standard solution for which you measured the absorbance.) Use 3 significant figures. Molarity (μmol/L) = Your Answer: 23.20 No Points Possible 8) Part I. Data Entry No Scoring. You diluted a portion of the BROMOTHYMOL BLUE standard solution #1 to make standard solution #2 . Please enter the precise volume of the bromothymol blue standard solution #1 in milliliters used to prepare standard solution #2. Note that in making this solution you measured out the volume of buffer with your volumetric pipet and NOT Bromothymol Blue.
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Your precision should be to a hundredth of a milliliter, e.g. 15.00 mL. Volume (mL) = Your Answer: 20 No Points Possible 9) Part I. Data Entry No Scoring. You diluted a portion of the BROMOTHYMOL BLUE standard solution #1 with the pH 8.0 buffer to make standard solution #2 . Please enter the total volume of the resulting bromothymol blue standard solution #2 you prepared. Your precision should be to a hundredth of a milliliter, e.g. 50.00 mL. Volume (mL) = Your Answer: 30 No Points Possible 10) Part I. Scoring scheme 3-3-2-1. Calculate and enter the molarity of BROMOTHYMOL BLUE standard solution #2 . You should report your molarity to 3 significant figures, e.g. 31.5 µmol/L.
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This note was uploaded on 04/10/2010 for the course CHE 2a taught by Professor Tingguo during the Winter '08 term at UC Davis.

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Spectroscopy Mixture 1 Post-Lab - Q# Question Text 4) Part...

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