University Of Chicago

• CHEM 113

Introduction: The purpose of this lab was to use qualitative analysis, or the testing of a substance or mixture to determine its chemical constituents, to identify the anions and cations of 14 unknown solutions. Identification was achieved by observing such things as physical appearance, appearance under a flame, pH levels, and reactions with other solutions. Qualitative analysis, as opposed to quantitative analysis, works only to determine the components of a mixture and does not regard the amount of each solution. Several tables are given so that laboratory results may be compared, and components of the unknowns may be extrapolated. In addition to the following tables of possible cations and anions and common flame test results, a table listing the general physical appearance of several solutions is given (pertinent results outlined later). To aid in the determination of solutions, solubility tables from Oxtoby’s “Principles in General Chemistry” were used. Cations Anions H + ClLi+ OHNa+ NO3 - K + SCNAg+ SO4 2- NH4 + CO3 2- Mg2+ Ba2+ Co2+ Cu2+ Zn2+ Sr2+ Al3+ Fe3+ Common Flame Test Results Elements Flame Color Li Red K Weak violet, red by cobalt blue glass Na Strong, persistent yellow Ba Yellow green (pale) Cu Green (blue green) Sr Carmine (a strong to vivid red) Ca Strong red-orange Pb Pale blue As Bluish white Sb Pale green/bluish Zn Whitish green (blue-green) Fe Gold Mg Bright white P Bluish green (pale) B Bright green Experimental: The procedure was followed without divergence from the lab manual. Zhao, Mieshan. General Chemistry Lab Manual. University of Chicago. 2013. Data: Table 1: Initial Observations Solution Number Observations 1 Clear (colorless), slight smell of ammonia 2 Clear (colorless) 3 Clear (colorless) 4 Clear (colorless) 5 Clear (colorless) 6 Yellow/Orange, Translucent, Odorless 7 Clear (colorless) 8 Clear (colorless) 9 Clear (colorless) 10 Clear (colorless) 11 Clear (colorless) 12 Pink, Translucent, Odorless 13 Clear (colorless) 14 Blue, Translucent, Odorless Table 2: Litmus Test Results Solution Number Red Paper 1 Basic 2 No Change 3 No Change 4 No Change 5 No Change 6 No Change 7 Basic 8 No Change 9 No Change 10 Basic 11 No Change 12 No Change 13 Acidic 14 No Change Table 3: Flame Test Results Solution Number Flame Color 1 No Color 2 No Color 3 Red 4 No Color 5 Yellow/Green 6 No Color 7 Bright Yellow Flame 8 No Color 9 No Color 10 Red 11 Violet Flame 12 No Color 13 No Color 14 No Color Solution 1: NH4OH Although solution 1 was colorless, it gave off a scent distinctive to ammonia. Thus the cation was determined to be NH4 + . As for the anion, the litmus test revealed that solution 1 was basic. Since 1 didn’t react with the barium in solution 5, the only option left for the anion was hydroxide. Solution 1 and 12: green-like precipitate Co2+ (aq) + OH- (aq)  Co(OH)2 (s) (1) Solution 1 and 6: dark orange precipitate Fe3+ (aq) + OH- (aq)  Fe(OH)3 (s) (2) Solution 1 and 14: dark blue precipitate Cu2+ (aq)+ OH- (aq)  Cu(OH)2 (s) (3) Solution 1 and 2: white precipitate Zn2+ (aq) + OH- (aq)  Zn(OH)2 (s) (4) Solution 1 and 8: white precipitate Ag+ (aq)+ OH- (aq) AgOH (s) (5) Solution 1 and 13: tiny amount of white precipitate Al3+ (aq) + OH