Analysis of Ni. by Spectrophotometry This exam involves using best practices to

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Analysis of Ni. by Spectrophotometry This exam involves using best practices to analyze a N unknown solution. Multiple working standard solutions will be prepared by diluting a stock solution of NiSO4. The 0.200M stock solution will be the highest concentration standard: it has been analyzed to give the table (below) of absorbances as a function of wavelength. This analysis will be done by spectrophotometry. Measurements are done in 1.20 cm cuvettes. The stock solution, glassware, and the spectrophotometer are provided. Everything else is your responsibility. Waveleng Absorbance Plot an absorption spectrum. Attach the graph to this exam after this sheet of paper. Locate the wavelength value of maximum absorbance. Indicate this wavelength on the graph and record the value below. th (nm 380 390 400 410 420 430 440 450 460 470 480 490 500 0.746 1,026 0.853 0.619 0.417 0.229 0.142 0.094 0.066 0.054 0.036 0.022molar absorption coefficient change? Why? From the absorption spectrum, calculate the value of the molar absorption coefficient at E 1.02 4.275 M'cm (1.20) (0.200M) If you change the concentration of the solution, will the NO, Moior absoi Ption cotff icitnt is used to clescrmune 0.028 520 530 0.066We lngth, itis independent of Concentianon 540 0.046 50, on Changing Conctnnianon, it clots not Change 550 560 570 580 0.057 0.078 0.093 0.106 0.143 0.349 From the 50.0 mL of 0.200M NiSO4 stock solution provided, prepare five dilutions. Use the 0.200 M NisOs stock solution as your highest concentration standard solution You will need standard solutions with five different curve. All your standards must have absorbances above 0.1 Attach a sheet of paper with all the dilution calculations for your series of standards, after your absorption spectrum. (12) Mc VC Md x Vc s peumconcentrations plus the blank to draw your calibration ho sol btron OF NIS

Explanation / Answer

The solution which is provide to you is 50mL 0.2M NiSO4. Your asked to make it as your highest concentration standerd.

Let us make 5 different solution with this stock solution

1. You have one 0.2M NiSO4 solution

2. Let us make a 0.1M NiSO4 solution: 10mL 0.2M NiSO4 solution + 10mL solvent

Total volume 20 mL and the concentration is 0.1M

You can calculate it by M1V1=M2V2 equation as well. To elaborate, here M1=0.2, V1=10mL V2=20mL. Therefore M2=0.1.

3. Let us make 0.05M NiSO4 solution:

This can be done by two ways:

Case1. 10mL 0.1M NiSO4 and 10mL solvent. You can easily have 20mL 0.05M NiSO4.

Case 2. 5mL 0.2M NiSO4 and 15mL solvent. Here M1=0.2, V1=5mL, V2=20mL; therefore M2=0.05

4. Let us try 20mL 0.025M Solution:

This can be done by three procedure

Case 1: 10mL 0.05M NiSO4 and 10mL Solvent

Case 2: 5mL 0.1M NiSO4 and 15 mL solvent

Case 3: 2.5mL 0.2M NiSO4 and 17.5mL solvent

5. Since you can not dilute 0.0125mL as your absorption became less than 0.1. You have to make another standerd.

Let us make 20mL 0.08M solution.

M1=0.2 V1=2mL M2=0.08M, V2= 2*0.2/0.08 = 5mL. So you have to add 3mL solvent to a 2mL 0.2M NiSO4 solution.

Now you have 5 standerd and a blank(only solvent). You can easily make a calibration curve.

Hope this will help. Cheers!!

Feel free to ask if you have any doubt.

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