Part C Calibration Of The Uv Vis Spectrophotometer 10 Measure And Record The Spectral Absorbance Of Each Solution Pre 1 (65.32 KiB) Viewed 22 times
Part C Calibration Of The Uv Vis Spectrophotometer 10 Measure And Record The Spectral Absorbance Of Each Solution Pre 2 (50.22 KiB) Viewed 22 times
Part C: Calibration of the UV/Vis spectrophotometer 10. Measure and record the spectral absorbance of each solution (prepared in step 4) at the wavelength of maximum absorbance for acidified potassium dichromate. Question 6: Plor your data in a graph of spectral absorbance against concentration Remember to include your reference sample, which has a concentration of OM K:Cr0 in OMH SO. Question 7: Is there a trend in the data you have collected? If there appears to be a linear trend draw a line of hest fit. Do wour results support the Lambert Beer Law Part D: Testing for ethanol in the breath 1. Fill two 25 mL calibration flasks with approximately 18 mL of distilled water and label one with the title 'mouthwash. 2. Place a long plastic straw in the unlabelled flask such that the end is in contact with the base of the glass. Take a deep breath and slowly exhale through the straw such that your breath is bubbled through the water. 3. With the help of your demonstrator, rinse your mouth with the supplied mouthwash and repeat step 12 using the labelled flask. 4. Fill each flask to the calibration line with distilled water and mix each solution. 5. Accurately pipette a 5.0 mL aliquot of 0.0040 M K Cr2O7 in 2.0 M H2SO4 to each of two clean, dry test tubes. To each tube, slowly add with shaking 4 mL concentrated H2SO4 from a bottle-top dispenser. Hazard: Do not exhale further than what feels comfortable. Forceful exhalation can cause inhalation of the liquid! Hazard: Be careful not to ingest the mouthwash. 16. Accurately pipette 1.0 mL of each aqueous breath sample to a separate tube of acidified dichromate solution and heat in a 50 °C water bath for 10 minutes (make sure to record which solution contains the mouthwash' sample). Note Heating this mixture accelerates the oxidation of ethanol to acenic acid.
17. Allow the solutions to cool and record the spectral absorbance at the wavelength of maximum absorbance for acidified potassium dichromate) of each sample in a clean spectrophotometric cell. Remember to use 2.0 M H2SOx solution as a reference, as used previously Question 8: Calculate the initial concentration of potassium dichromate in the samples (UV/Rebreath samples) prepared for spectral analysis Question 9: Using the calibration plot prepared in Part C determine the final concentration of potassium dichromate in each UV/Vis breath sample (after heating) Question 10: Knowing the initial and final concentrations of potassium dichromate, calculate the concentration of ethanol present in each UV/Vis breath sample. Question 11: Lakine into account the series of dilutions you performed and the fact that the average inspiratory capacity (deep breath and non-forceful exhale) of males and females are 38 and 2.4 L, respectively calculate the concentration of ethanol in each breath Question 12: An ethanol concentration of 0.0155 mM in the breath roughly corresponds to a blood alcohol concentration (BAC) of 0.15%. Determine your BAC using the results from both breath tests. Comment on the validity of testing for BAC after rinsing with mouthwash
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