You have been given six numbered pipets containing 0.50M solutions of the sodium salts Na2CO3, NaHCO — Acid-Base Titration and Qualitative Analysis Chemistry Question
Problem Context
You have been given six numbered pipets containing 0.50M solutions of the sodium salts Na2CO3, NaHCO3, NaHSO3, NaH2PO4, Na2HPO4, Na3PO4, not necessarily in this order, a 50-mL beaker containing 0.40M HCl, and a pipet containing methyl orange indicator. Devise and carry out an experiment to determine to contents of each pipet, providing both qualitative and quantitative data to justify your conclusions.
Give a brief description of your experimental plan.
Model Answer
Excellent Student Results:
Student presented an organized plan to add a fixed number of drops of each of the unknowns, a fixed number of drops of the methyl orange indicator to each unknown, and then add HCl drop wise until a color change occurs. Student planned to note the color changes, drops added, and a detectable odor for the sulfite solution.
Record your data and other observations.
Model Answer
A sample data table quantifying the HCl added might look like this:
Excellent Student Results:
Student showed a carefully constructed data table OR written account of data collected including all color changes, number of drops added to reach color changes, extent of bubbling including size of bubbles, and odor produced. Multiple trials were performed.
Based on your observations, write the relevant equations that led to your conclusions:
Model Answer
Excellent Student Results:
Student included each of the six ionic equations that correlated to the reactions performed from data table, correctly indicating ion charges, states symbols, and stoichiometric relationship.
Conclusions
Model Answer
Key:
Vial #1: Na3PO4
Vial #2: NaHSO3
Vial #3: Na2CO3
Vial #4: NaH2PO4
Vial #5: NaHCO3
Vial #6: Na2HPO4
Excellent Student Results:
Student correctly identified each of the six unknowns and gave justifications that were consistent with the data taken in this experiment.