Experiment 1 SDSU - Lab report PDF

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Abdulazeez ALSadoon Lab Partner: Roxie

2/5/2020

Chem 201, Experiment 1 Introduction to the Spectrophotometer and Beers Law Procedure See the Pre-lab report on Page 26 of my laboratory notebook for an outline of the overall general procedure. The stock blue solution used in this experiment was called Erioglaucine Disodium which had a concentration of 7.7 x 10^-6 M as presented on the solution.

Experimental Data Part: Measurement of the Visible spectrum of the Dye Solution

The wavelength of Light λ

Visible Absorption values(A)

(nm) 375

0.052

395

0.092

415

0.104

435

0.025

455

0.017

475

0.02

495

0.028

515

0.043

535

0.068

555

0.124

575

0.252

595

0.392

615

0.751

635

0.9150

655

0.306

675

0.056

690

0.014



The Peak of my graph occurs at 635 nanometers with an absorption of 0.9150



This data peak of 635 nanometers is used for the measurement of absorbance vs concentration for part two data.

Part 2: Beer’s Law Graph

Solution

1 2 3 4 5

Amount of

Amount of DI

Stock Solution

water (mL)

(mL) 0 1 2 3 4

DI water 4 3 2 1

Absorbance

Concentration (M)

0 0.184 0.363 0.563 0.750

0 1.54*10^-6 3.08*10^-6 4.62*10^-6 6.16*10^-6

Calculated Results: 

The Value for εl is 134,090 M^-1

Sample Calculations Solution 2: Sample Calculations C1V1=C2V2 (7.7 x 10^-6 M) (1 mL) = (‘x” M) (5 mL) (7.7 x 10^-6 M*mL) = (“x” M) (5mL) (7.7 x 10^-6 M*mL)/5 mL = “x” M 1.54 X 10^-6 M = “x” M Part 2: how to Calculate εl 

A = εlc o Y=mx+b 

B=0 in this experiment because when the absorption value is equaling to zero, so the concentration value is

o Y=mx 

y/x=m 



C = Concentration



Absorbance = 1



εl= A/c

which is equivalent to εl=A/c

o εl = 1/M o εl = 134,090 M^-1 (0.826) Absorption / (6.16 * 10^-6) = 134,090 M^-1

Discussion: For the Experiment in Part 1, I have observed that the peak of the graph with the blue colored stock solution at 635 nanometers with absorption value of 0.9150. The graph represented a steady incline before peaking as the wavelength went up as well, similarly to the absorption. After the peak, there was a significant decline of absorption values even with high wavelengths. As the absorption value represents 0.9150, this indication shows that the blue stock solution’s visible absorption spectrums could be found between the wavelengths of 375 and 635 nanometers. Anything beyond the 635 nanometers is out of range to measure the amount of light that the stock solution could absorb. The color of the liquid dye only became lighter as we started diluting it with water. As for my Beers law graph, my graph was very linear, however my line does not go through 0, and as the concentration has increased, the absorption value has increased as well. Some of the errors that could have occurred during the experiment is during the individual work of each student where we might have added more or less mL using the pipet that we were supposed to, high amount of dye solution compared to water which could cause error in the results. Another possibility for error is clicking the wrong button on the spectrophotometer machine which could result in wrong measurements and mess up our data’s and craft a wrong graph....