Lec_04 - Today 1. Report for Experiment 2 is due (40 pts)...

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Unformatted text preview: Today 1. Report for Experiment 2 is due (40 pts) 2. Post-lab for Experiment 2 is due (10 pts) 3. Unknown Summary Sheet for Experiment 2 is due (20 pts) 4. Pre-lab for Experiment 3 is due (5 pts) 5. Experiment 3. Qualitative Chemical Analysis have a write-up in your notebook Next week 1. Report for Experiment 3 is due (40 pts) 2. Post-lab for Experiment 3 is due (10 pts) 3. Unknown Summary Sheet for Experiment 3 is due (20 pts) 4. Pre-lab for Experiment 4 is due (5 pts) 5. Experiment 4. Acid-Base Titration have a write-up in your notebook Spring 2007 Experiment 3. Qualitative Chemical Analysis PURPOSE AND LEARNING OBJECTIVES To become familiar with the concept of qualitative analysis To learn to make and record scientific observations To introduce microscale techniques Qualitative Analysis deals with the detection and identification of the material (substance) of interest in a sample based on its physical and/or chemical properties. Gives a simple "yes" or "no" answer but doesn't determine actual amounts. In several cases, you use your eye as a detector! Example: Color change signifies the detection of species of interest Spring 2007 Microscale Techniques Chemistry is done on microscale! Used for small size samples: to reduce cost to reduce the amount of generated waste due to limited sample size and availability to increase throughput (more rapid analysis), easier automation Applications: drug discovery, HTS (high throughput screening) molecular diagnostics medical diagnostics Spring 2007 Microwell Plates 6-well plate 384-well plate Well working volume: > 2 ml Well total volume: ~ 10 ml Well working volume: 10 125 l Well total volume: 100 130 l 96-well plate 1536-well plate Well working volume: 0.1 0.3 ml Well total volume: 0.3 0.4 ml Well working volume: 2 10 l Well total volume: 12 l 1 l = 103 ml = 106 L Spring 2007 Experimental Procedure Mix aqueous solutions in pairwise fashion Make observations as to changes that happen!!! Take note of changes, such as formation of precipitates and color of precipitates Spring 2007 Known Solutions Acids: 0.1 M HCl hydrochloric acid 0.1 M H2SO4 sulfuric acid 0.1 M HNO3 nitric acid Inorganic Salts: 0.2 M Ba(NO3)2 barium nitrate 0.2 M AgNO3 silver nitrate 0.1 M K2CrO4 potassium chromate 0.1 M Na2S sodium sulfide Base: 0.1 M NaOH sodium hydroxide 0.1 M Fe(NO3)3 iron (III) nitrate 0.2 M Ni(NO3)2 nickel nitrate Spring 2007 Data Collection. Known Solutions ppt precipitate, w white, y yellow Spring 2007 Unknown Solutions Subset of 10 known solutions A B C D E Spring 2007 Review: Nomenclature of chemical species chromate ion, CrO42 chromic acid, H2CrO4 Spring 2007 Review: what cations and anions are stable in aqueous solution? Stable Cations Stable Anions 1L Based on having a stable octet of valence electrons like their nearest noble gas element Spring 2007 Review: solubility trends of different salts Know how to use Appendix 2 (Solubility table) Spring 2007 Chemistry behind it Balanced molecular equation: Fe(NO3)3 (aq) + 3 NaOH (aq) Fe(OH)3 (s) + 3 NaNO3 (aq) Full ionic equation: Fe3+ (aq) + 3 NO3 (aq) + 3 Na+ (aq) + 3 OH (aq) Fe(OH)3 (s) + 3 Na+ (aq) + 3 NO3 (aq) Net ionic equation: Fe3+ (aq) + 3 OH (aq) Fe(OH)3 (s) Fe3+ + 3 OH Fe(OH)3 (s) OR Discussion: include the reactions for all of your known solutions not just the unknowns! Spring 2007 Miscellaneous Tips One set of known solutions available per 3 students. Be a good neighbor! Be careful not to cross-contaminate the solutions in the bottles If you accidentally dipped the tip of the dropper bottle into your solution, wipe it off immediately with the Kimwipe FINISH your unknown identification in class Discussion: 11 balanced molecular plus 11 balanced net ionic equations, 22 equations total! Spring 2007 ...
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