Question

7. The Absorption Spectrum of Cobalt(II) Chloride Procedure Getting Started 1. Your laboratory instructor may ask that you work in groups rather than alone. 2. Obtain directions from your laboratory instructor for discarding the solutions that you will use in'! this experiment. 3. Obtain instructions for using your spectrophotometer. 4. Obtain your unknown. Making the Measurements 1. Mark each of 7 dry 18 x 150-mm test tubes with one of a series of identification numbers running from 1 to 7. 2. Use Mobr pipets to make the additions of 0.150 M CoCl, and distilled water shown in the table below. CAUTION: Never use your mouth to draw liquid into a pipet, even if the liquid is water. Use a rubber suction bulb or some other suction device. Test Tube No. 0.150 M CoCl2 Solution (mL) 5.0 Distilled Water (mL) 4.0 1.0 3.5 2.0 2.0 3.0 4.0 1.0 3. O 2 Thoroughly mix the contents of each test tube by gently shaking the test tube from side to side. Do not use one of your fingers as a stopper. . M1 - 4 = M2 J2 ) (0.5)(x) = x(5).. Test Tube Volume (mL) of 0.150M Volume (mL) Dilution Concentration Co(CI) de-ionized water 1 5.0 .15 4 .0 1.0 12 3 3.5 1.5 105 3.0 2.0 9 5 2.5 - 2.5 75 6 2.0 3.0 1.0 4.0 .3 *4 = x.

Answer 1

I have checked your work, which is excellent!

According to Beer's law: A = k.C.l

Where 'A' is the absorbance of the solution, which is dimensionless.

'k' is molar absorptivity of the Cobalt(II) chloride

'C' is the concentration of the solution (the dimension is mol/L or 'M')

'l' is the path length = 1 cm (in general)

Therefore, A = k.C cm

Here, 'C' is in mol/mL

Therefore, the dimension of 'k' = dimension of A/C.l = 1/(M * cm) = M^-1.cm^-1