Weak acid Strong base

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VIDEO LINKS:

Lab Experiments (Write protocols and perform experiments based on these):

  1. Preparing the Burette
  2. Calibrating the pH Probe
  3. Titration of Weak Monoprotic Acid
  4. Titration of Weak Diprotic Acid

Optional Experiments

  1. Making 0.1 M NaOH Solution
  2. Standardization of NaOH Solution
  3. Making 0.1 M Acetic Acid Solution

The prelab must include Experimental Protocol, Chemical Table and Equipment Table.

The lab report requires all sections (including prelab sections) to be completed in one document.

Experimental Protocol

  1. (Analysis) Watch the experiment videos. Take notes on the protocol.  Stop the video and re-watch as necessary to acquire the details of the procedure.  Write out the protocol for each part of the experiment.  (It can be written in sequential steps.  Complete sentences are not necessary.)  This is the protocol you will follow, so be detailed.
  2. (Manipulation) Assume that you are titrating 15.0 mL of the 0.1 M HOOCCH3 solution with the 0.1 M NaOH solution. Calculate the volume of required NaOH solution to reach the equivalence point in this titration.
  3. (Existing knowledge, research and views) Define equivalence point.
  4. (Lab skills) Identify the method for knowing you have reached the equivalence point.
  5. (Acquiring competency) Identify the pH and conditions where the titration is considered completed and you stop titrating.

Chemical Table

(Representation) Prepare your chemical table including the materials you will use in the experiment.  Here is a general template that you may use.
Chemical Name Chemical Formula Molar Mass (g/mol) Hazards Reference PPE
Sodium Chloride NaCl 58.5 Skin irritation https://fscimage.fishersci.com/msds/21105.htm  
         
         
         
         
 

Equipment Table

(Analysis) Identify the equipment (type AND size) needed for the experiment and include the name and an image of each.  Be sure to describe the equipment, how to use it, and why it is suitable for this use.
Equipment Name Equipment Picture Intended Purpose

Data Collection

  1. (Acquiring competencies) Following your detailed protocol based on the videos, perform all the experiments. Record your observations and take pictures of your key steps in the process. Your observations and images need to be incorporated in your data section and this section should be as detailed as possible as you will use this information to complete your discussion.
  2. (Acquiring competencies) Follow your detailed protocol based on the videos. Filling your burette with the NaOH solution, perform the titration of the 0.1 M acetic acid with 0,1 M NaOH twice.
Titration A [NaOH]   [HOOCCH3]   Volume of HOOCCH3 solution (mL)
1 0.1 M 0.1 M 15
2 0.1M 0.1 M 15
  1. Optional (Acquiring competencies) Follow your detailed protocol based on the videos. Filling your burette with the NaOH solution, perform the titration of the 0.05 M maleic acid with 0,1 M NaOH twice.
Titration B [NaOH]   [HO2CCH=CHCO2H]   Volume of HO2CCH=CHCO2H solution (mL)
1 0.1 M 0.05 M 15
2 0.1M 0.05 M 15
  1. (Acquiring competencies) Following your detailed protocol based on the videos. Filling your burette with the acetic acid solution, perform the titration of the 0.1 M acetic acid and 0.1 M NaOH twice.
Titration C [NaOH]   [HOOCCH3]   Volume of NaOH solution (mL)
1 0.1 M 0.1 M 15
2 0.1 M 0.1 M 15
 
  1. (Representation) Create a table to record all your data from each titration. Include the total volume added, pH and color if an indicator was used. Calculate your expected equivalence point for each titration before you begin! Proceed slowly with small increments (0.2 ml) when you are within 5 ml of the equivalence point and 2 ml after. Continue to titrate until a pH of about 13.
Total volume (burette) acid or base pH Color Notes (before equivalence point, at equivalence point, after equivalence point)

Data Processing

  1. (Representation) Write the balanced molecular equations for the reaction in this experiment.
  2. (Representation) Write the balanced complete ionic equations for this experiment.
  3. (Representation) Write the balanced net ionic equations for this experiment.
  4. (Analysis) Classify the observed reactions.
  5. (Manipulation) Calculate the moles of HOOCCH3 in 15 mL of a 0.1 M HOOCCH3
  6. (Manipulation) Assume that you are titrating 15.0 mL of the 0.1 M HOOCCH3 solution with the 0.1 M NaOH solution. Calculate the volume of required NaOH solution to reach the equivalence point in this titration.
  7. (Manipulation) Calculate the concentration of the H3O+ and determine the pH after 15 mL of a 0.1 M NaOH reacted with the 15 mL of 0.1 M HOOCCH3
  8. (Manipulation) Calculate the concentration of the H3O+ and determine the pH after 7.5 mL of a 0.1 M NaOH reacted with the 15 mL of 0.1 M HOOCCH3
  9. (Representation) Draw the pH curves for each experiment from Titration A. (pH on the y-axis and mL NaOH added on the x-axis)
  10. (Representation) Draw the pH curves for each experiment from Titration C. (pH on the y-axis and mL HOOCCH3 added on the x-axis)
  11. (Interpretation) Find the equivalence point of your titrations on each graph for Titrations A and C.
  12. (Interpretation) Find the pH at the point half-way to the equivalence point on each graph for Titrations A and C.
  13. (Manipulation) Calculate the pKa for the weak acid from your titration curve and compare it to the literature value for the pKa of acetic acid.
  14. (Representation) Draw the pH curves for each experiment from Titration B. (pH on the y-axis and mL maleic added on the x-axis)
  15. (Interpretation) Identify the regions of your titration curves where you have a buffer solution. Could these same regions be identified on your titration curves for the strong acid strong base titration curves?
  16. (Assumptions and Analysis) Fill in the following table using the observations and data from your experiments.
Assumptions made Testing the assumption If assumptions are wrong ...
Acetic acid is a weak acid. Titrate it with a strong base. The equivalence point will be at pH=7.

Discussion

Write a minimum one-page (12 font, single spaced) discussion on the experiment conducted this week. Address at least one question in each category as fully as possible integrating the collected data, providing explanations for the observed trends, and evaluating whether your original assumptions about the experiment were validated by the results. The assignment will be graded on completeness, clarity of the explanations and the meaningful integration of the collected and calculated data. Correct grammar and appropriate format for the chemical formulae and chemical reactions is expected.
  1. (Existing knowledge, research, and views) Define weak acids, and provide at least one supported argument for the difference between a weak and a strong acid.
  2. (Existing knowledge, research, and views) Classify all your chemicals as acids or bases, strong or weak, monoprotic or diprotic, etc.
  3. (Existing knowledge, research, and views) Define pKa and provide at least one method for determining its value.
  4. (Existing knowledge, research, and views) Define conjugate pairs and describe how you would identify the conjugate pair of a weak acid.
  5. (Analysis) Predict how the shape of your titration curve would change if you titrated a diprotic or polyprotic weak acid instead of the acetic acid and provide at least one supported argument for your prediction.
  6. (Existing knowledge, research, and views) Define the equivalence point, and describe the steps involved in determining it for weak acid-strong base titrations.
  7. (Analysis) Compare the pH at the equivalence point from the HCl - NaOH titration to the pH at the equivalence point from the HOOCCH3 – NaOH titration using the same concentrations of acids and base. Describe at least one observed difference and provide a supported argument for the difference.
  8. (Existing knowledge, research, and views) Under what conditions can you use of the Henderson-Hasselbalch equation?
  9. (Assumptions) What assumption are we making about x when we drop it from an ICE table to avoid solving the quadratic equation?
  10. (Acquiring competencies) During the titration the solution is continuously stirred. Provide at least one supported argument for the necessity for stirring, and at least one method for carrying out the stirring.
  11. (Analysis) List every species of chemical in the flask after you add the first 2 mL of NaOH solution from the burette into the flask with the acetic acid solution. Indicate their relative amounts.
  12. (Analysis) List every species of chemical in the flask after you add the first 2 mL of acetic acid solution from the burette into the flask with the NaOH solution. Indicate their relative amounts.
  13. (Analysis) List every species of chemical in the flask at the equivalence point of the reaction between the NaOH solution from the burette into the flask with the acetic acid solution. Indicate their relative amounts.
  14. (Analysis) List every species of chemical in the flask at the equivalence point of the reaction between the acetic acid solution from the burette into the flask with the NaOH solution. Indicate their relative amounts.
  15. (Analysis) List every species of chemical in the flask after you add the 2 mL after the equivalence point of the reaction between the NaOH solution from the burette into the flask with the acetic acid solution. Indicate their relative amounts.
  16. (Analysis) List every species of chemical in the flask after you add the 2 mL of after the equivalence point of the reaction between the acetic acid solution from the burette into the flask with the NaOH solution. Indicate their relative amounts.
  17. (Analysis) Compare the pH at the equivalence point from the 0.1 M HOOCCH3 – 0.1 M NaOH titration with your calculated pH at the equivalence point. Assuming that your calculated value is the true value, comment on the accuracy of your experiment.
  18. (Analysis) Compare the pH at the point half-way to the equivalence point from the 0.1 M HOOCCH3 – 0.1 M NaOH titration with the pKa value of HOOCCH3 from the literature.
  19. (Analysis) Compare the titration curves between titrations A and C. Identify at least two differences between them and provide a supported argument for your choice.