Limiting Reactant (In Person)

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VIDEO LINKS:

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

  1. Limiting Reactant – Part 1
  2. Limiting Reactant – Part 2
  3. Limiting Reactant – Part 3
 

Data analysis and calculations (Use these if you need help with your data and interpretations)

  1. Interpreting Chemical Equations
  2. Reaction of Alka-Seltzer and Water
  3. Reaction of Alka-Seltzer and Vinegar
 

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

(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.

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. (Representation) Make sure to collect all the data that is required to fill out this table as you work your way through the experiment. The volumes are suggested amounts, update those with your measured values.
Experiment number Mass of tablet (g) Mass of cup (g) Volume of vinegar (mL) Volume of water (mL) Mass of cup with water and vinegar (g) Mass of cup with water and vinegar + mass of tablet (g) Mass of cup after experiment (g) Mass lost during the experiment (g)
1 0 35
2 5 30
3 10 25
4 15 20
5 20 15
6 25 10
7 30 5
8 35 0

Data Processing

  1. (Existing knowledge, research, and views) List the ingredients contained in Alka-Seltzer and their amounts.
  2. (Representation) Write the chemical equation for the reaction that occurs when Alka-Seltzer dissolves in water.
  3. (Representation) Write the chemical equations for the reactions that occurs when Alka-Seltzer reacts with vinegar.
  4. (Manipulation) The mass lost during the experiment is the carbon dioxide gas that bubbled out of your solution. Using the mass of the carbon dioxide from the experiments and the chemical equations from questions 2 and 3, calculate the mass of the sodium bicarbonate in each tablet. (Hint: There will be 8 calculations.) Write each calculation with the appropriate units.
  5. (Manipulation) Using the previously calculated masses of sodium bicarbonate and the measured mass of each tablet, calculate the consumed sodium bicarbonate percentage of each tablet. (Hint: There will be 8 calculations.) Write each calculation with the appropriate units.
  6. (Representation) Organize your calculated values in the following table and plot the volume of vinegar on the x axis and the percent for the consumed mass of the tablet on the y axis.
 
Experiment number Volume of vinegar (mL) Mass of generated CO2 (g) Mass of consumed NaHCO3 (g) Consumed NaHCO3 percentage of tablet (%)
1 0
2 5
3 10
4 15
5 20
6 25
7 30
8 35
  7.(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 ...
There is sufficient water to dissolve all the sodium bicarbonate. Dissolve the same tablet in a larger volume of water and compare the residue.
The citric acid is the limiting reactant in the Alka-Seltzer tablet.
   

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. (Analysis) Describe what happens when vinegar is added to water.
  2. (Analysis) Describe what happens when Alka-Seltzer is added to water.
  3. (Interpretation) Using your balanced chemical equation that describes the observed reaction of the Alka-Seltzer in water, interpret its meaning on the microscopic and macroscopic scale.
  4. (Analysis) Bubbles of CO2 formed during your reactions. Provide at least one argument for why the CO2 molecules didn’t remain in the solution.
  5. (Analysis) Provide and argument in favor of using a scale that reads to the hundredth place for this experiment.
  6. (Analysis) Provide a valid reason for waiting until there are no more bubbles produced or present in the solution before recording the final mass of the reaction.
  7. (Analysis) Identify which measured and calculated values would change if you stopped the experiment early. Predict if the values would increase or decrease as a result of rushing the experiment.
  8. (Interpretation) Using your balanced chemical equation that describes the observed reaction of the Alka-Seltzer with vinegar, interpret its meaning on the microscopic and macroscopic scale.
  9. (Analysis) If Alka-Seltzer undergoes a reaction even when dissolved in water, provide a supported argument for using vinegar.
  10. (Assumptions) The difference in mass between the starting materials and the reactants is the gaseous carbon dioxide that was produced. Describe at least one assumption that would make this statement valid.
  11. (Interpretation) Describe your graph. Identify at what volume of vinegar added did the sodium bicarbonate become the limiting reactant.
  12. (Assumptions and limitations) The mass of CO2 lost between the different cups changes because the amount of vinegar used increased between additions. Describe at least one assumption regarding the limiting reactants that would make this statement valid and one that makes it not valid. Use your graph to support your arguments.
  13. (Analysis) Identify the limiting reactant when only water or a small amount of vinegar was used. Provide numerical evidence to support your argument.
  14. (Analysis) Identify the limiting reactant when a large amount of vinegar was used. Provide numerical evidence to support your argument.
  15. (Analysis) Compare your % NaHCO3 in an Alka-Seltzer tablet with the manufacturer’s data. Comment on the accuracy and precision of the experiment.