Solution Manual For Laboratory Manual for General, Organic, and Biological Chemistry, 3rd Edition

Date Name Section Team Instructor Pre-Lab Study Questions 16 1. How can the presence of an ion in a solution be detected? Ions can be detected by adding a substance that chemically reacts with the ion. 2. What tests would you use to identify a solution of Ag3PO4? For the Ag1+ : add NaCl and HNO3 For the PO43-: add HNO3 and (NH4)2MoO4 3. What tests would you use to identify a solution of FeCl3? For the Fe2+: add KSCN For the Cl1-: add AgNO3 4. A flame test of a colorless solution gives a bright yellow color. When reacted with AgNO3 a white precipitate forms that dissolves when HNO3 is added. When HCl is added to the unknown solution, bubbles form. What is the compound in the colorless solution? Flame test→ Na1+ AgNO3 test → Cl1HCl test →N/A unknown is NaCl Copyright © 2014 Pearson Education, Inc. Date Name Section Team Instructor REPORT SHEET LAB Testing for Cations and Anions 16 1. Unknown solution number: Unknown X A. Flame Tests for K + , Ca2+ , and Na+ ions Cation Tested Color produced 2. K+ Pink-purple 3. Ca 2+ Orange-red 4. Na + Yellow-orange 5. Unknown Purple 6. From your test results, does your unknown contain K+ , Ca 2+ , or Na + , or none of these? K Explain your choice. Unknown X flame test was purple colored B. Tests for ammonium ion, NH4+ , and Iron(III) ion, Fe3+ Cation 1. NH 4 + Test Results (Known) Test Results (Unknown) Odor Color Odor Color Ammonia Turns blue No odor No color change No odor Dark red No odor 2. Fe3+ From your test results, does your unknown contain 3. NH4+ or Fe3+ , or none of these? Explain your choice. Unknown X was KSCN since the test caused a red color change. Copyright © 2014 Pearson Education, Inc. Dark red Fe3+ C. Tests for Negative Ions (Anions) Anion Observations (Known) Observations (Unknown Solution) 1. Cl − White solid forms, does not dissolve in HNO3 White solid forms, does not dissolve in HNO3 White solid forms, does not dissolve in HNO3 White solid forms, dissolves in HNO3 2. SO42− 3. PO43− Yellow solid forms No solid 4. CO32− Gas bubbles form No bubbles 5. Identification of the negative ion in the unknown solution From your test results, what negative ion (anion) is present in your unknown? Explain your choice. Unknown formed a white solid that did not dissolve in HNO3 Cl1- D. Writing the Formula of Your Unknown Salt 1. Cation Fe3+ Name Iron (III) ion Anion Cl1- Name Chloride ion 2. Formula of your unknown salt FeCl3 3. Name of your unknown salt Iron (III) chloride E. Testing Consumer Products for Some Cations and Anions Product tested Window cleaner Cation tests Observations Flame tests (Na + , K+ , Ca 2+ ) Ion(s) present NC NH 4 + Odor, turns blue Fe3+ NC NH41+ Anion tests Cl − White solid forms, does not dissolve in HNO3 SO42− NC PO43− NC CO32 − NC Copyright © 2014 Pearson Education, Inc. Cl1- Questions and Problems Q1 How do the tests on known solutions containing cations and anions make it possible for you to identify the cations or anions in an unknown solution? When a test done on a known has the same results as the unknown, you can conclude you have the same ions present. Q2 You have a solution that is composed of either NaCl or CaCl2 . What tests would you run to identify the compound? The flame test would give different colors for each cation. Q3 If a solution turns a deep red color with a few drops of KSCN, what cation is present? Fe3+ Q4 A plant food contains (NH4 )3PO4 . What tests would you run to verify the presence of the NH 4 + ion and the PO43− ion? For NH41+: add NaOH, test with red litmus paper For PO43-: add HNO3 and (NH4)2MoO4, look for yellow solid Q5 Write the symbol of the cation or anion that gives each of the following reactions: Cl1- a. Forms a precipitate with AgNO3 that does not dissolve in HNO3 CO32- b. Forms a gas with HCl Na1+ c. Gives a bright, yellow-orange flame test SO42- d. Forms a precipitate with BaCl2 that does not dissolve in HNO3 Copyright © 2014 Pearson Education, Inc.