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CH204 Experiment 7b - concentration 3 Part 4 –...

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3/29/2010 1 Part 3 of Experiment 5 1 Part 1- Sample Preparation 1. Weigh out 0.15 g of green crystals and dissolve in deionized water. a) Measure the crystals in a weigh boat, not in the volumetric flask. b) Transfer the dissolved sample to a 25 mL volumetric flask. 2. Add 8 mL of 6 M H 2 SO 4 , and fill to the line with deionized water using a disposable pipette. 3. Your sample is now dissolved in 25 mL of solution. 2 4. Pipette 5 mL into a 30 mL beaker, add about 10 mL deionized water, heat and stir. Start the reaction right away! 5. Add KMnO 4 dropwise until the solution turns pink. (Around 30-50 drops.) Yellow colorless pink. 6-7. Transfer the pink solution to a 25 mL volumetric flask and let it cool on the dark part of the lab bench. 8. Cool to room temperature. 9. Fill the volumetric flask to the mark using deionized water. The sample has now been diluted 1 to 5 from the original concentration.
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Unformatted text preview: concentration. 3 Part 4 – determination of the iron content in coordination compound sample. 1. Add 10% hydroxylami ne s ADD 2mL of hydroxylamine instead of 1 mL in step 1. 2. Add sodium acetate 3. Add 8 mL 0.3% 1,10 phenanthroline and mix 4. Add 0.3% 1,10 phenanthroline to mark on flask and mix well! 5. Measure and record the absorbance 6. You want an absorbance reading that is between your lowest and highest standard. (Absorbance between 0.1 and 1.0) 4 7. If it’s too high, do another dilution and test it again. s RECORD ALL DILUTIONS ! s RECORD ALL MEASURED ABSORBANCE VALUES ! 8. Make all of your dilutions 5 ml to 25 ml. 9. Do your reading in triplicate – that is, use three different samples. a) They can be the same concentration that you use to measure three times b) Or you may use three different concentrations. 5...
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