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28 Nov 2019

Preparation of Required Solutions

(NOTE: the methanol is used in the NP solution simply to make the solvent conditions analogous to the NPA solution)

measure out 13.9 mg of NP (139.11 g/mol) - record the mass; place into a 100 ml volumetric flask

add 30.0 ml methanol; mix to dissolve

dilute to 100.0 ml total volume with deionized water; mix well

take 5.0 ml of this solution and place in separate container; add 45.0 ml deionized water; mix well

QUESTION: what is the [NP] in the NP stock solution?

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Elin HesselLv2

9 Feb 2019

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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,

Can someone please help me complete this worksheet

B. 0.036

C. 0.36

I need help answering d and e

Determinatrion of Iron in Vitamin

A. Prep of Iron Soln. from Vitamin

Weigh three vitamin tablets and place each tablet in separate 125-mL Erlenmeyer Flask. Add 25 mL of 2M HCL to each flask in the hood and boil the samples for 15 mins.

Set up Vacumm filter system and filter each sample serparetely and collect the filtrate(liquid). Transfer filtrate after each run to a 50 mL Volumetric flask. Rinse filter flask with DI water and transfer rinse to the vol. flask as well. Repeat for each solution.

After solutions cool, dilute it to the mark with DI water and Mix well. Transfer contents to a labeled beaker.

For each solution made, transfer 1.00 mL of the solution with a volumetric pipette and place it in a fresh 50 mL vol. flask. Then dilute it ot he mark with DI water.

B. Prep of sample Solutions

From each diluted vitamin solution a test solution sample will be made. Using a vol. pipette transfer 5.00 mL of the diluted vitamin solution(unknown molarity) to a large test tube. Then add 4.00 mL hydroquinone and 6 mL of o-phenanthroline to the test tube with a vol.pipettes. Note the volume of the test solutions. This dilution step is needed when calculate the mass of iron in the tablets.

C. Prep of Sample Solutions

One iron standard solution will be made for the class.

D. Prep of Calibration Solutions

Each student pair will make at least one calibration solution. Have the instructor assign you a solution 0-7. The entire lab section will make one calibration set by the following steps:

Label a 50.00 mL vol. flask with your assigned number (0-7)

Collect ~ 5 mL of hydroquinone and transfer it to a clean beaker. Then collect ~ 5 mL of phenathroline and transfer this solution to another clean beaker. Transfer 2.00mL of hydroquinone and 3.00mL of phenathroline using vol. pipettes to the labeled vol. flask

Collect ~5-10 mL of the standard solution and transfer it to a clean beaker. The amount of iron solution to transfer via vol. flask is equal to the assigned number (i.e. if your group was assigned #1, transfer 1.00 mL of the iron solution to the flask. Flask 0 will not contain any iron solution.

Once all three reagents have been added to a flask. Add ~ 20mL of DI water. Mix the solution by capping the flask and inverting it several times. Continue adding DI water to the mark on the flask and mix solution again by inversion.

What is the molarity of the iron in each calibration solution?

Given Info/Data


Mass of Iron in Tablet from bottle (mg)	18
Mass of Iron for Stock Soln. (g)	0.1435
Molar Mass of Fe(NH₄)₂(SO₄)2â¢ 6H₂O (g/mol)	392.14
Molar Mass of Fe (g/mol)	55.845
Moles of Iron Stock Solution (mol)	0.000365941

Mass of Iron tablets: 1.2900g 1.2991g 1.2979

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