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UCLA CHEM 14CL - Guidelines

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Chem 14CL Spring 2006This is an individual reportChem 14CL Spring 2006This is an individual reportReference all the materials (whether online or from a book / journal) that you used for this part of the reportChem 14CL Spring 2006 Post-lab Report Guideline for the Vitamin C Analysis Experiment This is an individual report (I) ABSTRACT – Summarize the goal(s) and technique(s) for the experiment plus a summary of your experimental result(s). (II) DATA AND OBSERVATIONS Organize all your data and observations in a tabulated format for the standardization of sodium thiosulfate and the analysis of vitamin C. Your data should include the weights of various solid reagents and/or chemicals; all the volumes for the titrations as well as the color of the solutions before and after the addition of the starch. (III) DATA ANALYSIS (SHOW ALL YOUR WORK AND REASONING) Note: End point for this experiment refers to the change in the color of the solution from blue to colorless after adding the starch. Period 1 – Standardization of the Sodium Thiosulfate Solution (i) Calculate the molar concentration of the standard KIO3 solution (ii) Using the initial volume and the end point volume, calculate the molar concentration of Na2S2O3 for each trial of the standardization (iii) Calculate the average molar concentration of Na2S2O3 solution Period 2 – Analysis of the Vitamin C Tablet Note: From here on, use the AVERAGE concentration for the sodium thiosulfate solution for the following calculations. (iv) Using the initial volume and the end point volume, calculate the number of moles of Na2S2O3 added to the vitamin C solution for each trial of the analysis (v) Calculate the moles of I3- reacted with Na2S2O3 for each trial of the analysis (vi) Calculate the moles of I3- reacted with vitamin C tablet for each trial of the analysis (vii) Determine the moles of vitamin C presented in the solution for each trial of the analysis (viii) Determine the grams of vitamin C presented in the solution for each trial of the analysis (ix) Based on your result in (viii), calculate the % by mass of ascorbic acid in the vitamin C sample for each trial of the analysis (x) Calculate the average % by mass of ascorbic acid in the Vitamin C sampleChem 14CL Spring 2006 Post-lab Report Guideline for the Vitamin C Analysis Experiment This is an individual report (IV) ERROR ANALYSIS (SHOW ALL YOUR WORK AND REASONING) Note: You may assume the absolute error for the 250mL volumetric flask to be ±0.20mL. Absolute errors for other common laboratory glassware are listed on page 27 of the lab manual. (i) Calculate the % RAD for the sodium thiosulfate solution (ii) Calculate the % inherent error in the KIO3 solution. (iii) Calculate the % inherent error in the sodium thiosulfate solution for ONE of your standardization trials. (iv) Calculate the % RAD for % by mass of ascorbic acid in the vitamin C sample. (V) DISCUSSIONS Dr. F.R. Klenner invented the Vitamin C therapy in 1940s. Write a brief summary (no more than half a page) of his idea and why he believed that vitamin C could be used to cure most of the diseases. Reference all the materials (whether online or from a book / journal) that you used for this part of the report (VI) CONCLUSIONS Summarize your results Comment on the % inherent error in the sodium thiosulfate solution. Hint: Based on the % inherent error in the sodium thiosulfate solution, what can you conclude in terms of the precision of the standardization? Explain your reasoning Comment on the % RAD for the % by mass of ascorbic acid in the vitamin C sample. Hint: Based on the % RAD for the % by mass ascorbic acid, what can you conclude in terms of the precision of the standardization? Explain your


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UCLA CHEM 14CL - Guidelines

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