CHEM 2040U Study Guide - Volumetric Flask, Graduated Cylinder, Pipette

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31 Jul 2012

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All glassware used in this experiment was rinsed with 1 m hcl (aq) followed by type 2 water prior to use. Transfer pipettes and volumetric flasks were all grade a. aqueous solutions were prepared with type 2 water. %transmittance was measured using a spectronic 20d+ spectrophotometer and a single 10 mm borosilicate glass cuvette. 50 ml of creek water collected from location a was pipetted into a 250 ml beaker using a 25 ml transfer pipette. 2 ml of concentrated hcl was then added via a transfer pipette and the sample was brought to a gentle boil using a hot plate. After boiling for 20 minutes, the sample volume had been reduced to approximately 20 ml. The acidified sample was removed from the hot plate and allowed to cool to room temperature. After confirming that no solid particles were visible, the sample was quantitatively transferred to a 50 ml volumetric flask.

Related Questions

Obtain a sample of steel. Rinse it with acetone to remove any oil and dry briefly. Weigh three samples of 0.5g of steel into 150 mL beakers.
Add about 50 mL of 6 M HNO3 to each sample and boil gently for 5-10 minutes. Then carefully add 1 gram of ammonium peroxydisulfate and boil gently for another
10-15 minutes. Add additional 6 M HNO3 if necessary to keep the solution volume at 30 - 50 mL.
Cool the solutions to room temperature, and transfer each to 250 mL volumetric flasks. Dilute to the mark with deionized water and mix well. Accurately transfer three 20.00 mL aliquots of each sample into individual beakers.
Treat them as follows:
Aliquot mL 85% H3PO4 mL std. Mn soln. grams KIO4

1 5ml 0.4g

2 5ml 0.4g 5ml

3 5ml 0.0g

Boil each of the treated aliquot solutions gently for 5 minutes.

Cool each solution to room temperature and quantitatively transfer each to 50 mL volumetric flasks. Dilute to the mark with deionized water and mix well.

When all three aliquots are ready, set the spectrophotometer at a wavelength of 525 nm, and measure the percent transmittance (to the nearest 0.1%) the aliquots.

Aliquot 1. 50.1%
Aliquot 2. 9.2%
Aliquot 3. 100.3%

Convert all transmittance data to absorbance, then calculate and report the percent manganese in each portion of the unknown analyzed,

A 0.500g sample is analyzed spectrophotometrically for manganese by dissolving it in acid and transferring to a 250 mL flask and diluting to volume. Three aliquots ae analyzed by transferring 50 mL portions with a pipet to 500 mL Erlenmeyer flask and reacting with an oxidizing agent, potassium peroxydisulfate, to convert the manganese to permanganate. After reaction, these are quantitatively transferred to 250 mL volumetric flasks, diluted to volume and measured spectrophotometrically.

By comparison with standards, the average concentration of the final solution is determined to be 1.25 x 10^-5M. What is the percent manganese in the sample?

A 25 mg brass sample was placed in a 25.0 mL volumetric flask. The sample was prepared according the procedure outlined in this lab and its transmittance was measured to be 35%. Use your experimental graph to determine the mass percent of copper in the sample. Show all calculations.

CHEM 2040U Study Guide - Volumetric Flask, Graduated Cylinder, Pipette

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