Molar Concentration of Stock and Vitamin C Mass Lab Worksheet

Format for the Formal Laboratory Report

Submitted as a file (doc, docx, pdf) to the Post lab report quiz AND to TurnItIn

 

Title Page for Canvas submission: A separate page with the following information: experiment title, your name, the teaching assistant’s name, course and section number and the date the lab was performed.

Title Page for TurnItIn submission: Do not include your student number or full name in the text of the report or on the title page (which you are asked to do for the Canvas submitted report).  Instead you can use your first initial and last name along with your TA name and section number on the TurnItIn title page.

 

The rest of your report should be identical for the Canvas and TurnItIn submission.

Introduction: Two or three (2-3) paragraphs describing why this experiment is important within the scope of society and stating what the experiment is designed to accomplish.  Include relevant balanced equations and a description of specialized equipment where appropriate.

Procedure: A brief summary of what was done in the experiment. Reference the lab procedure on Canvas.  DO NOT RECOPY!  Instead, include the specific details and quantities used, and in particular, any deviations from the given procedure should be noted. This is written in the past tense and in the passive voice, (no personal pronouns).  For Example: “A burette was filled …”; NOT “I filled a burette…”.  Complete sentences must be used. The point of including the details of the procedure is to allow someone else to be able to reproduce your experiment. 

Data/Observations/Calculations: For this, you simply need to submit your excel calculations and post-lab report quiz. Make sure to include the units for all data recorded. Observations should be recorded. 

Calculations: If you don’t populate the excel file with calculations, you MUST show a complete example of the calculations used to interpret the data. Make sure your handwritten calculations and data are clear… circle, underline, tabulate, or otherwise list clearly the final answers. You do not want the reader to have to hunt for the answers. Units must be given at each stage of the calculations and, if required, an estimate of the experimental uncertainty should be calculated. Each type of calculation should be represented. For example, if you do multiple ‘average’ calculations throughout the report, you only need to show one (1) example.

Discussion and Conclusion: These are the most important sections of the report. This is your chance to show you understand and can interpret the data. Discuss how theories are proved or disproved by your data and how sources of uncertainty affect the results. Remember, we don’t care about human-based error. Observations, expected results, and comparison with known values should also be discussed when appropriate. Summarize your results. Conclusions are drawn from the interpretation of the data and any explanations as to what happened in the experiment are stated here. Questions given in the post-lab report quiz are good points to address.

References: This is the last section of a scientific paper. References should be presented in a list at the end of the report and numbered in the order of appearance in the text, tables, or figures. Details of this can be reviewed from the library module section 6.8 Citation Styles. 

Experimental Procedure for LAB G: Volumetric Analysis of Vitamin C

 

Part A

  1. In a clean 250 mL beaker, dissolve a single tablet of vitamin C in 100 mL of distilled water with continuous stirring using a stir plate and magnetic stir bar.
  2. Stir thoroughly for ~10 minutes to ensure that all the vitamin C has dissolved (there will be an insoluble residue of ‘filler’ from the tablet). Use a glass stir rod to gently help break up the tablet and stir for 5 more minutes.
  3. Quantitatively transfer the solution through a gravity filtration set up into a 500-mL volumetric flask, washing the beaker and filter paper with small aliquots of distilled water, and make up to the mark with distilled water. Make sure to rinse the glass stir rod and stir bar. Return the stir bar to your TA. Stopper and thoroughly mix the flask contents by inverting the flask at least 10 times.

 

Part B

  1. Rinse and fill a burette with the provided sodium thiosulphate solution. The TA will give you the concentration during the lab.
  2. Pipette 25.00 mL of the dilute standard KIO3 solution into a 125 mL Erlenmeyer flask. Add 0.2 g KI using a level portion of KI in the scoop provided. Add 1 mL of 1M sulfuric acid with a plastic transfer pipette (20 drops). Add 10.00 mL of vitamin C solution with a pipette. Mix thoroughly. The vitamin C will react with some of the iodine.
  3. You will now determine how much iodine is left over (how much did not react with the vitamin C). Record the initial burette reading to 2 decimal places. Titrate the contents of the Erlenmeyer flask, slowly, with stirring, until a pale yellow colour is obtained. Add ~20 drops of starch solution and continue the titration until the blue colour just disappears. Record the final burette reading.
  4. Repeat the titration at least twice more in order to obtain consistent results. Titrations must agree within ±0.2 mL. Average the titration volumes.

 

Waste

Dispose of any unused KIO3 solution (both concentrated and dilute) and unused Na2S2O3 in the provided inorganic waste containers. All other solutions may be poured down the drain.

 

Experiment G: Volumetric Analysis of Vitamin C

word image 899 WASTE:

  • Collect remaining dilute and concentrated KIO3 in the waste container

SAFETY:

  • Safety glasses
  • Wear gloves where appropriate
  • Sulphuric acid is corrosive

NOTES:

  • Make a new dilute primary standard from the concentrated KIO3 solution saved from lab F
  • Titrations should agree within 0.2mL
  • Your vitamin C will react with the I2 generated from the first reaction, the remaining I2 will then be back-titrated with sodium thiosulfate according to the third reaction equation
  • ERROR/UNITS/SIGFIGS required on every number reported!
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