Qualitative Analysis - DOC

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					Qualitative Analysis of Household Compounds
Sue Harmon-Oak Forest High School 1-708-687-0500 ext. 3712 Goal: To use simple chemical and physical tests to correctly identify seven white solid compounds commonly found in the home. The solids will be chosen from the following list: Compounds used as unknowns Source sodium chloride table salt (uniodized)) sodium bicarbonate baking soda sodium hydroxide drain opener (lye) calcium carbonate chalk calcium sulfate plaster of paris starch cornstarch fructose fruit sugar sucrose table sugar magnesium sulfate Epsom salts

Test reagents phenolphthalein extracted from laxative tablets iodine (tincture) vinegar distilled or deionized water CuSO4-NaOH-Na2CO3 (Clinitest urine sugar test tablets) Na2CO3 (washing soda)

Quantity provided about 3 mL about 3 mL about 10 mL about 200 mL 1 tablet, broken about 2 grams

Equipment provided spot plate or well plate wash bottle w/distilled water conductivity tester (9v LED)

glass rod or toothpicks for stirring scoopula or spatula dropper

General rules for this event: 1. Students will work as individuals. 2. Students must wear safety glasses and follow all standard safety practices. Taste-testing is specifically prohibited. 3. Each student will receive about 3 grams of each unknown and the listed quantities of the test reagents. These will not be refilled. 4. Each student may bring in one 4x6" note card with prepared notes/procedures. No other notes or references are allowed. Calculators are neither needed nor permitted.

Score will be the number of unknowns correctly identified. Time will be used as a tie-breaker. Background information An article in the Journal of Chemical Education (Qualititative Analysis of Eleven Household Compounds, Solomon, JChEd 68:328, April 1991) provides the basis for this experiment (but a number of alterations have been made). Analytical tests include solubility in water, iodine test for starch, acid test for carbonate, precipitation reactions, copper(II) reduction of monosaccharides, phenolphthalein for base. Significant changes from the cited procedure are: 1. Students will not have to prepare any reagents. All will be in ready-to-use form. 2. Students will use spot plates or well plates for testing. 3. Conductivity testers are used for the final test to distinguish salt from sugar. 4. The test for MgSO4 is changed from that in the above Journal article. Addition of Na2CO3 produces insoluble MgCO3. This replaces formation of Mg(OH)2 by addition of NaOH. 5. Students may modify the procedure if desired, but must follow usual safety practices and use only the materials provided. General procedure: 1. Test solid for solubility. Use several drops of water and a very small sample of solid. 2. Iodine test for starch: Add 1 drop of tincture of iodine to any insoluble sample in water. Dark blue/black color indicates presence of starch. 4. Phenolphthalein test for NaOH: Add 1 drop phenolphalein to the sample solution. Bright pink/red color is positive for NaOH. [Lighter pink color may be observed with NaHCO 3.] 5. Sodium carbonate test for MgSO4: Add a few grains of Na2CO3 to the sample solution. White precipitate is positive for magnesium sulfate. (This is a change from the JchEd article--solutions of NaOH will not be provided.) 6. Vinegar test for NaHCO3 and CaCO3: Combine a few drops of vinegar with a small amount of unknown. The evolution of CO2 indicates the presence of the carbonate or bicarbonate. 7. CuSO4 test for reducing sugar: Add about ¼ of a test tablet to the sample solution. A red/yellow color indicates the reduction of Cu 2+ by fructose. 8. Conductivity test for NaCl: Put a small amount of sample solution in a well and test. (NaCl is an electrolyte.)

Analytical Scheme
NaCl, NaHCO3, CaSO4, NaOH, MgSO4, CaCO3, Cornstarch, Sucrose, Fructose Water

Insoluble CaSO4, Cornstarch, CaCO3 Iodine

Soluble NaCl, NaHCO3, NaOH, MgSO4, Sucrose, Fructose Phenolphthalein

Brown CaSO4, CaCO3

Blue Cornstarch

Colorless NaCl, MgSO4, Sucrose, Fructose Na2CO3

Pink NaOH (dark) NaHCO3 (light)

Vinegar Vinegar Bubbles CaCO3 No change CaSO4

Bubbles NaHCO3

None NaOH

No reaction NaCl, Sucrose, Fructose CuSO4 tabs

White ppt. MgSO4

Red/yellow ppt. Fructose

No reaction NaCl, Sucrose Conductivity

Electrolyte NaCl

Nonelectrolyte Sucrose

Qualitative Analysis
Name_____________________________________ School____________________________________ Session__________ Time_____________

***SET NUMBER_________ ***OMISSION OF SET NUMBER RESULTS IN DISQUALIFICATION*** Match the numbered unknowns with the lettered compounds listed at right. letter for each sample: 1. __________ 2. __________ 3. __________ 4. __________ 5. __________ 6. __________ 7. __________ A. calcium carbonate B. calcium sulfate C. fructose D. magnesium sulfate E. sodium bicarbonate F. sodium chloride G. sodium hydroxide H. starch I. sucrose Write the correct

Number correct____________ Place__________