Experiment #4 Report (1)

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Brown University *

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0330

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Chemistry

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Feb 20, 2024

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Name ___________________ Section_____________________ TA _____________________ Date _______________________ EXPERIMENT #4 CHEM0330 Laboratory Report How Can Eleven Colorless Solutions be Chemically Identified? INSTRUCTIONS : Use your laboratory manual, pre-lab materials and laboratory notebook to answer the following questions. Please record your answers on some version of this document and not in your laboratory notebook, or on other types of paper. This report is due the night before your next lab session (Week of 10/30). When you submit to Gradescope, you will be asked to assign each question to a page or multiple pages. It is important you do this to facilitate the grading process, and reports without assigned pages are subject to grade deductions moving forward. 1. Identify the solutions by matching the solution number with the chemical formula. In the evidence column, cite all of the observation(s) you made that led to your assignment. You are likely to have multiple pieces of evidence for several unknowns. You should not be writing the net ionic equations that led to the identification in this question. The observation should be specific and descriptive (i.e. Observed a white precipitate upon mixing with AgNO 3 ; purple-colored flame observed) Weekday of your lab:_______________ Unknown Identity Evidence 1 2 3 4 5 6 7 8 9 10 11

2. Reflect (3-4 sentences) : Was your pre-lab flow chart efficient for identifying each unknown? Why or why not? For procedures that required adjusting during the experiment, what changes did you make, and describe the ambiguous results that led to you making changes. If your pre-lab procedure worked perfectly, describe how you set yourself up for success. 3. Draw the flow chart for the procedure that you used in lab to arrive at the solution identities in Question 1. Use the example on Manual Page 5 as a reference for how to properly set this up. Your flowchart must clearly show when/how you identified each unknown (i.e. The flowchart example does this by bolding/underlining the unknown when it is identified in the scheme). Do not include any chemical reactions or net ionic equations in the flow chart.

4. Use all of the information in the Experiment #4 manual to write a balanced chemical equation AND net ionic equations (if applicable) for each of the following combinations. State if these reactions are precipitation reactions, redox reactions, both or neither. If no net reaction occurs, you can write ‘no reaction’ . Make sure to include all phases of matter (s, l, g, aq), and note that the some of the following chemicals may not have been unknowns in Experiment #4. a. Ammonium oxalate mixed with sodium hydroxide b. Silver nitrate mixed with sodium hydroxide c. Manganese chloride mixed with hydrogen peroxide and sodium hydroxide d. Zinc(II) nitrate mixed with sodium thiosulfate

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5. Describe how mixing aqueous solutions of AgNO 3 and Na 2 CO 3 ultimately results in the formation of Ag 2 O, and classify this reaction as precipitation, redox, both or neither. How is this reaction different from the formation of Ag 4 O 4 (or AgO, as described in Equation 10 in the manual)? Classify Equation 10 as precipitation, redox, both or neither as well. 6. After mixing HCl with an unknown solution you speculate contains the thiosulfate anion, you were unable to confirm the identity of the unknown through the odor of SO 2 . How else could you unambiguously confirm the identity of the unknown solution through this reaction? 7. A very accident-prone student named Natalie approaches her TA after rapidly testing all eleven solutions via flame test and claimed they all contained sodium. Propose a reason why Natalie could have come to this conclusion.