LAB Report Experiment 2 CHM260 - UV-VISIBLE DETERMINATION OF AN UNKNOWN CONCENTRATION OF KMnO4 SOLUTION PDF

Preview

Summary

CAWANGAN TERENGGANU KAMPUS BUKIT BESIDIPLOMA IN INDUSTRIAL HYGIENE AND SAFETY TECHNOLOGY(AS1213B)CHM260 LAB REPORT EXPERIMENT 2 :UV-VISIBLE DETERMINATION OF AN UNKNOWN CONCENTRATIONOF KMnO 4 SOLUTIONPREPARED BY:NAME STUDENT ID GLORIA CASSANDRA SALUTAN 2020883318 FARINA ATHIRAH BINTI ROHAIZAT 2020625...

Description

CAWANGAN TERENGGANU KAMPUS BUKIT BESI DIPLOMA IN INDUSTRIAL HYGIENE AND SAFETY TECHNOLOGY (AS1213B) CHM260 LAB REPORT EXPERIMENT 2 : UV-VISIBLE DETERMINATION OF AN UNKNOWN CONCENTRATION OF KMnO4 SOLUTION

PREPARED BY: NAME

STUDENT ID

GLORIA CASSANDRA SALUTAN

2020883318

FARINA ATHIRAH BINTI ROHAIZAT

2020625768

ATHIRAH FILDZAH BINTI MULIADI

2020839522

PREPARED FOR: DR. AHMAD ROZAIMEE MUSTAFFA

DATE OF SUBMISSION: 10 DECEMBER 2021

THEORY UV-Vis spectroscopy is an analytical technique that measures the amount of discrete wavelengths of UV or visible light that are absorbed by or transmitted through a sample in comparison to a reference or blank sample. It is influenced by a factor which includes the sample composition where it could provide information on what is on the sample and the concentration. This spectroscopy technique relies on the use of light. The spectrophotometer consists of light source, a sample compartment and a detector. Spectrophotometers that measure in the UV and visible region consists two general types which are scanning and diode-array as opposed to UV-Vis spectrophotometer which it contains a monochromator that usually consists of holographic gratings that allow lights of individual wavelength to be sequentially imparted to the sample. Moreover , the method of spectrophotometer is to use absorbance of light by an analyte which is potassium manganate (KMnO4) at a certain wavelength to determine the unknown concentration. The instrument UV-Vis Spectrophotometer uses UV light and a visible port of electromagnetic spectrum.

OBJECTIVES 1. To determine potassium permanganate maximum wavelength. 2. To plot the potassium permanganate calibration curve. 3. To determine the unknown solution concentration of potassium permanganate

APPARATUS 1. Beaker 2. Burette 3. Glass rod 4. Volumetric flask 100mL 5. Dropper

CHEMICALS 1. Potassium permanganate KMnO4 2. Distilled water

PROCEDURE A. Preparation of the KMnO4 standard solutions. 1. The solid of KMnO4 was weighted about 0.01g or 10mg using the weighing boat. Then, the KMnO4 was transferred into the 100mL of volumetric flask using the filter funnels. 2. A little bit of distilled water was poured into the volumetric flask to dissolve the solid. Then, place the stopper on a volumetric flask and shake vigorously. The distilled water once again pours until the calibration mark and shakes the solution. 3. Then, the stock solution was poured into the beaker and was labeled as 100ppm stock solution.

4. 5mL of stock solution was transferred into the 100mL of volumetric flask by using a burette. The distilled water was poured into the flask until the calibration mark. 5. The flask was labeled as a 5 ppm solution. 6. Step 4 and step 5 were repeated by using 10mL, 15mL and 20mL stock solutions and transferred into a small beaker. 7. The beaker was labelled as 10ppm, 15ppm and 20ppm.

B. Preparation of the unknown 1. The stock solution was pipet between 5 to 20mL by using burette and transfer into the flask. The distilled water was added until the calibration mark. 2. The stopper was placed on the flask and was shaken until the solution was homogenous. 3. The solution was transferred into the beaker and labeled as unknown.

C. Determination of absorption maximum λmax 1. The cuvette was obtained and clean and rinsed with distilled water and then was filled with distilled water about ¾ of the cuvette. 2. Wipe the cuvette with kimwipe. 3. The cuvette was labeled as blank. 4. Step 1 and step 2 were repeated by using the 5ppm, 10ppm, 15ppm and 20ppm with different cuvette. 5. Label the cuvette as 5ppm, 10ppm, 15ppm and 20ppm solution.

D. Operation of the UV-Vis Spectrophotometer Instruments: Varian/Cary 50 UV-Vis Spectrophotometer Operation instruction 1. The carry win UV icon was selected and click scan. 2. Click the setup, and start was set to 800, stop was 400 scan controls was fast, y mode and y-min were set to absorbance and zero respectively. 3. The baseline was click and set to correction. Then, click the report and filled in our experiment title. 4. In the auto store icon, it was set to prompt at start. Then click ok. 5. The blank was placed into the instrument and the baseline was clicked then clicked ok. After the baseline show it was zero click finish, print and then place the cuvette with different concentration. 6. Then print the results. 7. The start icon was clicked and the wavelength was set the same as step 2. There were three replicates. 8. In the standard icon, filled the standard and concentration. The fit type was linear direct and filled in the number of samples. 9. Step 5 and 6 were repeated.

E. Determination of the unknown concentration 1. The concentration icon was clicked. 2. Setup is chosen, cary icon is clicked, the maximum wavelength λmax is keyed in. 3. Replicate = 3 was selected.

4. ‘Standard’ icon was clicked, the ‘calibrate during run’ function was checked. 5. The calibration standard until (mg/L) and the number of the standard samples was set. 6. The fit type (linear direct) was selected. 7. Sample icon is chosen, the number of the samples are selected and the unknown was keyed in. 8. Report icon was clicked, operator name and the comments were keyed in. 9. In the Auto Store icon, ‘storage on (prompt at start)’ was set. 10. To save the method, ‘file → save method as → ok was clicked. 11. The ‘BLANK’ cuvette was put and ‘zero’ was clicked. 12. The ‘BLANK’ cuvette was removed and the ‘SAMPLE’ cuvette was put. 13. Icon ‘start’ was clicked to start the concentration measurements.

REPORT PRE-LABORATORY QUESTIONS 1. Show how you will prepare a 5 ppm solution from a 100 ppm KMnO4 stock solution using a 100mL volumetric flask. Briefly describe the procedure. 5mL of the ‘stock’ solution was pipetted and was diluted with distilled water in a 100mL volumetric flask. The solution was transferred into a beaker and labeled as ‘5 ppm’. 2. What is the expected wavelength at maximum absorption, λmax for the KMnO4 solution? What is the ε value at this wavelength? (include the name, title, page number, etc of the reference you used to get the answer). The expected wavelength at maximum absorption λmax for the KMnO4 solution is 525.0nm. Value of A= εbc 0.562 =

ε

is equal to 5.63 x 10-9 Lmol-1cm-1.

ε (1cm) (5x 106 mg ) L

c = mol L mol = 5x 106 mg ฀฀ 1 x 103 ฀฀ L L 1mg mol = 3.1639 ฀฀ 107 mol L L

A= εbc 0.562 = ε (1cm) (3.1639 ฀฀ 107 mol )

L

0.562=

ε (3.169 ฀฀ 107 cm L-1 ) 0.562

1 mol 158.032 L

3.1639 X 107 L mol-1cm-1 ε = 1.77 x 10-8 L mol-1cm-1

QUESTIONS 1. Why is glass not a suitable cell material for use in UV spectroscopy? Glass will absorb some of the ultraviolet light and will cause an inaccurate result for the experiment as the reading will be higher than the exact one. 2. State one advantage of using the UV-Vis Spectrophotometer compared to a Spectronic 20 for this analysis. The advantage is to record absorbance at each wavelength and rapidly scan a range of wavelengths.

DISCUSSION The wavelength maximum absorption can be determined based on the graph of absorbance against wavelength by using uv-visible spectrophotometer. On a UVvisible spectrophotometer, the wavelength of maximum absorbance (max) of KMnO4 that we obtained is 525.60 nm. The colour that was absorbed was somewhere between green and yellow. This is true because the KMnO4 we obtained is purple in colour, thus the colour that absorbs will be the colour that KMnO4 does not exhibit, which is green. Next, the volume of KMnO4 which is 5 mL, 10 mL, 15 mL, and 20 mL are calculated into concentration in ppm which is 5 ppm, 10 ppm, 15 ppm and 20 ppm. The calibration curve was done by fitting the absorbance against concentration at the wavelength of maximum absorption. The absorbance concentration will be

represented by the x value. Beer-Law Lambert's states that the absorbance of a solution is directly proportional to its concentration. The Beer-Lambert Law equation, ฀ ฀ = ฀฀฀฀฀฀ , can also be used to compute the concentration of an unknown solution. We determined that the concentration of the unknown solution is 8.78 ppm, which is the same in both estimates. As a result, we may conclude that both methods can be used to determine a solution's unknown concentration. There are a few measures to take during this experiment to reduce the possibility of error. To avoid the parallax error, we must first align our eyes with the pipette scale. To remove any contaminants, we must rinse the pipette with KMnO4 before using it.

CONCLUSION According to these experiments, the absorbance of potassium permanganate was 0.0157 ppm^1cm^-1 and the maximum wavelength was 525nm. The Beer’s Law equation used to determine the concentration of unknown solution was 8.78 ppm with the correlation efficiency of graph and spectrogram was 1 and 0.9995 respectively.

DATASHEET EXPERIMENT 2 NAME AND INSTRUMENT: varian/ cary 50 UV-VIS Spectrophotometer Table 2.1: table of concentration and absorbance Solution

Concentration (ppm)

Absorbance

Standard 1

5

0.135

Standard 2

10

0.278

Standard 3

15

0.418

Standard 4

20

0.562

unknown

8.78

0.251

Mass of KMnO4 =

0.01

g

Graph without unknown sample concentration.

Graph with unknown sample concentration.

Show the sample calculation for the preparation of standard 3: ฀฀ × 100 ฀฀฀฀฀฀ = 15 ฀฀฀฀฀฀ 100 ฀฀฀฀

15฀฀฀฀฀฀ × 100฀฀฀฀ ฀฀= 100฀฀฀฀฀฀

฀ ฀ = 15฀฀฀฀

฀ ฀ = 15฀฀฀฀ of KmnO4 ‘stock’ solution is used to prepare standard 3 solution.

Concentration of unknown: The slope of the graph can be obtained by using the formula , ฀ ฀ =

฀฀2−฀฀1 ฀฀2−฀฀1

equation in which by

picking two points from the line in the graph and determining the difference in x-coordinates and y-coordinates of these two points and dividing them. ฀฀=

฀฀2−฀฀1 ฀฀2−฀฀1

(0.27) − (0.13) ฀฀= 10 − 5 ฀ ฀ = 0.0285

฀ ฀ = ฀฀฀฀฀฀ ฀฀ ฀฀= ฀฀฀฀ 0.251 ฀฀= (0.0285 ฀฀฀฀฀฀ − 1฀฀฀฀ − 2)(1฀฀฀฀) ฀ ฀ = 8.78฀฀฀฀฀฀

By using the Beer Law’s formula , ฀ ฀ = ฀฀฀฀฀฀ and the slope of the graph, m , the concentration of the unknown sample can be determined.

REFERENCES ● Mohd Noor, N. A. (2014). Experiment 2 CHM260. dokumen.tips. Retrieved December 10, 2021, from https://dokumen.tips/documents/experiment-2-chm260.html.

● CHM260 EXP 2 answer.docx - CHM 260 laboratory report experiment number 1 title the visible spectra of soft drink name Muhammad Yusri bin Hj Muhammad: Course hero. chm260 exp 2 answer.docx - CHM 260 LABORATORY REPORT Experiment Number 1 Title The Visible Spectra of Soft Drink Name MUHAMMAD YUSRI BIN HJ MUHAMMAD | Course Hero. (n.d.). Retrieved December 10, 2021, from https://www.coursehero.com/file/76704767/chm260-exp-2-answerdocx/...