We use cookies to give you the best experience possible. By continuing we’ll assume you’re on board with our cookie policy

Colorimetric Analysis: Manganese in Steel Essay Sample

essay
The whole doc is available only for registered users OPEN DOC

Get Full Essay

Get access to this section to get all help you need with your essay and educational issues.

Get Access

Colorimetric Analysis: Manganese in Steel Essay Sample

The goal of the experiment is to determine the percentage of Mn in an unknown metal sample by means of colorimetric analysis.
First stock solution of KMnO4 with known concentration was diluted and then carried to spectrometer for analysis. The peak with highest absorbance was taken as λmax. Then the molar extinction coefficient is calculated by plugging the value into the Beer-Lambert equation. Then the concentration of Mn2+ in unknown sample can be determined by scanning it in the spectrometer.1

UV/VIS Spectrophotometry is used to determine the absorption or transmission of UV/VIS light (180 to 820 nm) by a sample. A spectrometer is used in the process. Inside a spectrometer light from a source is separated into narrow bands by wavelength, pass through the sample and then measured by the detector.2 In this experiment UV/VIS Spectrophotometry is used to determine the absorbance of MnO4- ion in the solution.

Beer-Lambert law states that absorbance is proportional to the concentration of the absorbing species. The equation is A=ԐbC, where A is the absorbance, b is the path length, Ԑ is the molar extinction coefficient and C stands for concentration.2 In the experiment with the absorbance of MnO4- ion in stock solution determined by UV Vis spectrophotometry in part A and the absorbance in unknown sample was determined in part B, the concentration of Mn2+ can be calculated.

Experimental
There was no change in the experiment. 1
Results and Discussion (Sample # 2061)

Part A
Dilution of KMnO4
10mL transferred to 100mL volumetric flask: 9.9958mL x 0.003998M/100mL

10mL transferred to 100mL volumetric flask: 9.9958mL x 0.003998M/100mL

20mL transferred to 100mL volumetric flask: 9.9958mL x 2x 0.02M/100mL 20mL transferred to 100mL volumetric flask: 9.9958mL x 2x 0.02M/100mL

The wavelength used was 526nm.
A=ԐbC
Ԑ=A/bC= 0.935455/1×0.00039963=2340.8027 L mol−1 cm−1

Part B
Half-cell equations:
8H2O + 2Mn2+ —-> 2MnO4- +16 H+ +10e-
10e- +10H++ 5IO4—–>2MnO4- +5IO3-+6H+
Net balanced redox equation:
3H2O+ 2Mn2++5IO4—–> 2MnO4-+5IO3-+6H+
Calculation for KIO4:
1g x2%=0.02g

Molar mass of Mn2+=54.938g/mol
nMn2+=0.02/54.938=3.64046E-4mol
nKIO4=nMn2+ x2/5=9.10115E-4mol
mKIO4=9.10115E-4 x230.00037=0.2093g
Calculation for Unknown:
C=A/b Ԑ=0.462799/1×2340.8027=1.977E-4M
n=CV=1.977E-4 x 0.25L=4.9425E-5 mol
m=4.9425E-5 x54.938=2.7153E-3g
Mass of unknown:0.9629g
%Mn=2.7153E-3/0.9629 x100%=0.282%

Overall summary questions:
1. According to Beer’s law, the absorbance is dependent on the path length of the cuvette. Thus the value of observed absorbance will be lower if 1mm cell is used. The molar extinction coefficient is an intrinsic property, which means it would not change when the path length changes. 2. No the result would be less accurate. The change in absorbance around the highest peak is minimized thus the value derived from the highest peak is the most accurate and closest to the true value. Conclusion

In part A, by scanning the stock KMnO4 solution, the highest peak of absorption was found to be 526nm with absorbance of 0.935455. The molar extinction coefficient for Mn2+ was then calculated 2340.8027 L mol−1 cm−1. Then by scanning the sample solution at the wavelength 526nm, the absorbance was found to be 0.462799 and the concentration of Mn2+ in the sample was calculated to be 1.977E-4M. Thus the percentage of Mn2+ in the sample was calculated 0.282%. There are several possible sources of error in the experiment including error in readings of pipette, contamination of solution and sample may not completely dissolve. Reference

1. Ding, Z. Maslen, R; Stillman, M; Yeung, K. Chemistry 2272 Laboratory Manual; 2012 Ed; Dept. of Chemistry, London, ON, 2012-2013; p 6.1-6.5. 2. Harris, C.H, Quantitative Chemical Analysis, 8th ed.; W.H. Freeman and Company: New York, 2010

We can write a custom essay

According to Your Specific Requirements

Order an essay

You May Also Find These Documents Helpful

Osmosis Experiment

Materials: Potato cylinders, 20 percent sodium chloride solution, three test-tubes, test-tube rack, scalpel blade, Gel ink pen, syringe-10cm^3, Plastic ruler with mm, tile, forceps filter paper, Masking tape. Method: 1) Three test-tubes, A, B and C were labeled and initials of experimenters were applied with the date: January 29, 2013. 2) A syringe was used to put 10cm^3 of water in tube A and 5cm^3...

Laboratory Techniques and Measurements

A. Water boils at 100°C at sea level. If the water in this experiment did not boil at 100°C, what could be the reason? The reason why water did not boil at 100°C could be because we are not at sea level; the pressure could be lower. B. While heating two different samples of water at sea level, one boils at 102°C and one boils...

Absorption Spectroscopy: Beer-Lambert Law

Absorption spectroscopy is a practical way to find what the light absorption of a substance is, and whit this data combining the Beer’s law equation you can determine the concentration of different things in a solution, in this case using a orange Gatorade looking the concentration of its dye which is yellow dye #6 and what amount of this Gatorade sample is needed to kill...

Bio Potato Core Osmosis

Table 1: Weights of potato pieces Solutions for the potato pieces to be dipped in(M) | Mass of potato pieces in Grams (+/-0.01)(initial mass)| Time when the potato pieces were dipped in the solution in seconds (+/- 0.01)| Time when the potato pieces were taken out of the solution in seconds(+/- 0.01)| Mass of potato after a hour in Grams (+/- 0.01) (final mass)| Water...

Ocean County College

The purpose of this experiment was to construct a Beer’s Law Plot, determine the concentration of a sample using the Beer’s law plot, and to determine the concentration of Blue Dye #1 in a commercial product using visual Colorimetry. Procedure This lab consisted of calculating %T of given data and constructing a Beer’s Law plow. Secondly, The Beer’s Law data was used to extrapolate the...

Get Access To The Full Essay
icon
300+
Materials Daily
icon
100,000+ Subjects
2000+ Topics
icon
Free Plagiarism
Checker
icon
All Materials
are Cataloged Well

Sorry, but copying text is forbidden on this website. If you need this or any other sample, we can send it to you via email.

By clicking "SEND", you agree to our terms of service and privacy policy. We'll occasionally send you account related and promo emails.
Sorry, but only registered users have full access

How about getting this access
immediately?

Become a member

Your Answer Is Very Helpful For Us
Thank You A Lot!

logo

Emma Taylor

online

Hi there!
Would you like to get such a paper?
How about getting a customized one?

Couldn't Find What You Looking For?

Get access to our huge knowledge base which is continuously updated

Next Update Will Be About:
14 : 59 : 59
Become a Member