04_Ions_PostLab_Spr24

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Qualitative Analysis of Ions Ulani Rizo January 31, 2024

Ulani Rizo Qualitative Analysis of Ions Page of 2 9 CHM 113 POST-LAB Qualitative Analysis of Ions 1. Insert ONE picture of yourself in full PPE here ( include acetic acid ). **Remember to (1) show your full body so that we see you are wearing shoes; (2) wear your safety glasses, buttoned lab coat and gloves; (3) cover your lower legs (socks are not optional, even in Arizona); (4) tie back long hair in a ponytail or a bun; (5) remove jewelry. Full PPE with Acetic Acid

Ulani Rizo Qualitative Analysis of Ions Page of 3 9 2. Complete Table 1 based on the pH Test Strip tests that you performed in Part 1 of the experiment. 3. Complete Table 2 based on the qualitative tests you performed in Parts 2A – 2D in the experiment. The “indicator” in Table 2 is what you added to the known or unknown solution to test for the presence of the listed ion that resulted in the final observation. The indicator is NOT one of the 4 unknown ion solutions. 4. For each of the ion tests for known solutions in Table 2 (Parts 2A – 2D in the experiment), what type (or class) of reaction occurred? Hint: Refer to the reaction classes discussed in Sections 4.2 and 4.3 in your text. CO 3 2- ___________metathesis_______________________ SO 4 2- ___________precipitate________________________ PO 4 3- ___________precipitate________________________ Table 1: Test Strip Results of OH - and H + Solution Type pH Test Strip Color pH Acid or Base? Acetic Acid Yellow 5 Acid Sodium Bicarbonate Green 8 Base Table 2: Test Results Solution Type Indicator Observations Initial Final Carbonate Ion Bubbles Clear solution Clear solution with bubbles Sulfate Ion PPT Clear Solution White solution/ppt Phosphate Ion PPT present Clear solution White solution/ppt Calcium Ion PPT present Clear solution White ppt

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Ulani Rizo Qualitative Analysis of Ions Page of 4 9 Ca 2+ ___________precipitate________________________ 5. In this lab, you performed numerous qualitative tests (results are in Tables 1 and 2 above) that were then used to determine the identity of an unknown ion in solution. Fill in the table below with the results of your tests on your unknown solution. Note: The unknown solution can only contain ONE of the three ions (carbonate, sulfate, or phosphate) . Only one of the tests should be positive . To have a positive result, the observation should match the observation you noted in Table 2 for that particular test. • Also, prior to testing, the unknown solution should be clear; if it is cloudy you may get inaccurate results 6. Considering your observations for a positive result (indicated in Question 3) and your results for the unknown solution in Question 5, how would you know if a qualitative test was negative for an ion? Use one of your negative results from Table 3 compared to a positive result from Table 2 as an example to explain (in 2 - 3 sentences). 7. What is the identity of the ion in the unknown solution? Explain (in 2 – 3 sentences) using your results from Table 3 as evidence. Table 3: ‘Determination of Unknown’ Results Carbonate Ion Test Sulfate Ion Test Phosphate Ion Test Observation s Clear Solution White PPT Clear Solution Result: Positive or Negative? Negative Positive Negative When testing for a carbonate ion, you would apply acetic acid to indicate its presence. In table two when the acetic acid cam in contact with the carbonate it immediately began to bubble, releasing Carbon Dioxide gas. In table three we can see that when testing the unknown solution for the carbonate ion it did not have any bubble formation associated with the released of CO2 gas, therefore it is negative for possessing the carbonate ion.

Ulani Rizo Qualitative Analysis of Ions Page of 5 9 Unknown ion ___________________________ The identity of ion in the unknown solution is a sulfate ion. Unfortunately we were not given all the materials to perform this test however, both of the other tests I did came out negative and the lab procedure tells us that one of the test HAS to be positive, and the sample data shows us that the test came out positive for the sulfate ion.

Ulani Rizo Qualitative Analysis of Ions Page of 6 9 8. Identify and discuss TWO sources of error ( using 2 -3 sentences each ) for this experiment. How could you mitigate error for this experiment if you conducted it again? (“Human error” is NOT an acceptable source of error—be specific!) 9. Identify the equations below as a molecular equation ( M ), a complete ionic equation ( CI ), OR a net ionic equation ( NI ). a. __M__ AgNO 3 (aq) + NaCl (aq) AgCl (s) + NaNO 3 (aq) b. __M__ Na 2 CO 3 (aq) +2 HCl (aq) 2 NaCl (aq) + CO 2 (g) + H 2 O (l) c. __NI__ Pb 2+ (aq) + S 2- (aq) PbS (s) d. __CI__ Ca 2+ (aq) + 2 Cl - (aq) + 2 Na + (aq) + CO 3 2- (aq) CaCO 3 (s) + 2Na + (aq) + 2 Cl - (aq) e. __NI__ OH - (aq) + H + (aq) H 2 O (l) Error Source #1: No reaction occurring in the beginning between acetic acid and sodium bicarbonate due to poor dilution of the sodium bicarbonate in the distilled water. This could cause the solution to not be fully prepared for this experiment. Error Source #2: Mixing the wrong chemicals for any parts of the lab, causing for a false negative result. This could happen due to lack of focus or labeling. How to mitigate error: Make sure all solutions are fully prepared and ready before beginning any tests. For example ensuring that the sodium bicarbonate is fully dissolved into the solution. And ensuring that you label everything and focus on what chemicals are going where. → → → → →

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Ulani Rizo Qualitative Analysis of Ions Page of 7 9 10. Imagine that the unknown solution contains aqueous ammonium sulfate, which is commonly used in fertilizer. For the precipitation of barium sulfate after mixing aqueous ammonium sulfate solution and barium chloride solution (the reactants), write the (1) balanced molecular equation, (2) the complete ionic equation, (3) the net ionic equation AND identify the spectator ions, if any. Be sure to include the correct formulas for each compound, stoichiometric coefficients, and physical states. Hint: Refer to the solubility rules in the Introductory Materials page to determine the physical states of the products. Molecular Equation: Complete Ionic Equation: Spectator Ions: _____NH4(+1)_______ ______Cl(-)______ NONE Net Ionic Equation: BaCl2 (aq) + (NH4)2SO4 (s) → BaSO4 (s) + 2NH4Cl (aq) Ba(+2) [aq] + 2Cl(-1)[aq] + 2NH4(+1)[aq] +SO4(-2)[aq] → BaSO4[s] + 2NH4(+1)[aq] + 2Cl(-1)[aq] Ba(+2)[aq] + So4(-2)[aq] → BaSO4 [s]

Ulani Rizo Qualitative Analysis of Ions Page of 8 9 11. Imagine that the unknown solution contains potassium bicarbonate, which is frequently used as a pH buffering agent in foods and medications, and like sodium bicarbonate, will react with an acid. For the reaction between potassium bicarbonate solution and acetic acid solution (the reactants), write the (1) balanced molecular equation, (2) the complete ionic equation, (3) the net ionic equation AND identify the spectator ions, if any. Be sure to include the correct formulas for each compound, stoichiometric coefficients, and physical states. Hint: For guidance, refer to the equation shown at the beginning of Part 2 of the Procedure, the reaction between sodium bicarbonate and acetic acid. The products for the reaction in Question 11 will be analogous to the products in the reference equation. Molecular Equation: Complete Ionic Equation: Spectator Ion(s): ______K+______ ____________ NONE Net Ionic Equation: 12. Putting it all together! You ordered two chemicals, calcium carbonate and sodium carbonate, but the labels fell off in transit! How could you determine, using the qualitative tests and methods you used in this lab, which chemical is which ? KHCO3(aq) + HC2H3O2(aq) → KC2H3O2(aq) + CO2(g) + H2O(l) K(+1)[aq] + HCO3(-1)[aq] + HC2H3O2(aq) → K(+1)[aq] + C2H3O2(-1)[aq] +CO2(g) +H2O(l) HCO3(-1)[aq]+HC2H3O2[aq] → C2H3O2(-1)[aq] + CO2(g)+ H2O(l)

Ulani Rizo Qualitative Analysis of Ions Page of 9 9 We could figure out which chemical is which by conducting the following procedure. 1. Take a small amount of each chemical and place them into their own test tube. 2. Add a small amount of distilled water and swirl the test tube or stir with a stirring rod to ensure they are fully mixed. 3. View the results. The sodium carbonate should remain clear since NaCO3 is an aqueous solution. Calcium Carbonate is insoluble in water and therefore would produce a precipitate in water.

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