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Identification of Household Chemicals

Identification of Household Chemicals - OBJECTIVES YOU...

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10/10/2011 1 IDENTIFICATION OF HOUSEHOLD CHEMICALS FINAL EXERCISE – 105 Points Last Update: 10/10/2011 10:10 AM YOU determin determine and describe 7 properties of a substance sufficiently accurately to permit: OBJECTIVES other investigators to tell if they have the same substance from their determination of the same properties YOU, with those other investigators, Infer the Infer the identity identity of the substance by comparison of its 7 properties with those of a list of possible substances. Confirm the identity of the substance through an additional confirmatory test 2 Concepts: Acid Ammonia Base Confirmatory Test Flame Test High Temperature Behavior Isopropanol Known Substance Results Known Substances Melting Point Other’s Unknowns Others Results Other s Unknowns Partners pH of Aqueous Solution Posted Reaction with Iodine Solubility Tests Vinegar Water Your Results Your Unknown Oxidation / Reduction 3 Techniques: Solubility determination Reporting Observations Branched Procedures Apparatus: Test Tubes pH Paper Bunsen Burner Melting Point Apparatus 4 4 Solubility / Reactivity tests 1. Solubility in/Reactivity with Water 2. " Ammonia 3. " Vinegar 4. " Rubbing alcohol WHAT ARE THE SEVEN TESTS? 3 other tests 5. pH of aqueous solution of unknown 6. Reactivity with tincture of iodine 7. Behavior at high temperature 5 Why these four solvents? 1.Water - The most common terrestrial solvent (Extensive data on solubility in water exist, but hydrogen bonding makes it a complex ) 2.Aqueous ammonia - A basic aqueous solvent Likely to dissolve and react with acidic substances SOLUBILITY / REACTIVITY TESTS 3. Vinegar (aqueous acetic acid) - An acidic aqueous solvent Likely to dissolve and react with basic substances 4. Rubbing alcohol (isopropanol) - A non-aqueous solvent Likely to dissolve non-polar materials 6
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10/10/2011 2 t t t b HOW TO DO SOLUBILITY TESTS U ll Operational definition of solubility : Solid is soluble in solvent if ~20 mg 20 mg (1/4 spatulaful) or more dissolves in 2 mL mL of solvent ( 0.02g/1.00g = 1% solution ) @ ~20 o C test tubes Solubility can be accelerated by tapping test tube, or stirring rod) Use small using a thin glass rod 7 1. Behavior with tincture of Iodine: ( I 2 in alcohol ) Looking for evidence of REACTION , - i.e., c o l o r change, - Reaction has occurred if mixing with an aqueous solution bleaches the I 2 color Such substances are reducing reducing agents agents OTHER TESTS bleaches I 2 (alcohol) + 2e - 2I - Reducing agents give up electrons: R R + + e - e.g., vitamin C (ascorbic acid) , hypo 8 2. pH of aqueous solution Looking for [acidic / neutral / basic] property of aqueous solution of unknown.
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