Question

In: Chemistry

A solution of a specific vitamin has λmax = 287 nm and a concentration of 8.76...

A solution of a specific vitamin has λmax = 287 nm and a concentration of 8.76 × 10-7 M. The absorbance of the solution at 287 nm is A = 0.190. What is the molar absorptivity of the vitamin at 287 nm? (sample pathlength = 1.00 cm)

Solutions

Expert Solution

Solution :

Beer-Lambert Law

The absorbance of an electronic transition depends on two external factors.

1. The absorbance is directly proportional to the concentration (c) of the solution of the the sample used in the experiment.

                                                                                           A ∝ c

2. The absorbance is directly proportional to the length of the light path (l), which is equal to the width of the cuvette.

A ∝ l

Combining the two relationships,

                                                                    A ∝ cl

This proportionality can be converted into an equation by including a constant.

                                                                    A = εcl

This formula is known as the Beer-Lambert Law, and the constant ε is called molar absorptivity or molar extinction coefficient and is a measure of the probability of the electronic transition. The larger the molar absorptivity, the more probable the electronic transition. In uv spectroscopy, the concentration of the sample solution is measured in molL-1 and the length of the light path in cm. Thus, given that absorbance is unitless, the units of molar absorptivity are Lmol-1cm-1.

A = ε * c* ℓ

where

ε is the molar attenuation coefficient of that material

c is the amount concentration of those species;

ℓ is the pathlength.

λmax = 287 ,    C = 8.76 × 10-7 M ,               A = 0.190

ε = A/C*l =    0.190/ 8.76 × 10-7 *1        =    2.168 *10-2 *107

                                                                                             = 2.168 *105 Lmol-1cm-1


Related Solutions

Solution Concentration λmax Absorbance Color Region Blue # 2 Dilute 612.0 nm 0.314 Orange Blue #...
Solution Concentration λmax Absorbance Color Region Blue # 2 Dilute 612.0 nm 0.314 Orange Blue # 2 Concentrated 6.10.0 nm 0.667 Orange Red # 4 Solution Concentration λmax Absorbance Color Region A 1.00 x 10-5 0.506 0.208 Green B 2.00 x 10-5 0.506 0.442 Green C 3.00 x 10-5 0.506 0.607 Green D 4.00 x 10-5 0.506 0.874 Green Q3: Calculate the following for light with the same wavelength as the λmax found for an aqueous solution of concentered FD&C...
A 12.0M HCl solution has a density of 1.18g/ml. what is the concentration of this solution...
A 12.0M HCl solution has a density of 1.18g/ml. what is the concentration of this solution in the following units? a) weight percent b) molality thank you
In this experiment the concentration of Vitamin C/ascorbic acid is used to find the amount of...
In this experiment the concentration of Vitamin C/ascorbic acid is used to find the amount of iodine present through titration and the stoichiometric ratio. Furthermore, by finding the amount of iodine present before and after the equivalence point, the experiment presents us with the amount of iodine that reacts with the Vitamin C in “unknown B”.There were two titrations performed in this experiment, three times each. The first began with 50mL of Sodium Thiosulphate put in a burette. Approximately 2g...
Ascorbic acid (vitamin C, C6H8O6) is a water-soluble vitamin. A solution containing 81.0 g of ascorbic...
Ascorbic acid (vitamin C, C6H8O6) is a water-soluble vitamin. A solution containing 81.0 g of ascorbic acid dissolved in 220 g of water has a density of 1.22 g/mL at 55 ∘C. Calculate the mass percentage. Calculate the mole fraction. Calculate the molality. Calculate the molarity of ascorbic acid in this solution.
A solution of sulfuric acid has a concentration of 0.0980 g/L. If the density of the...
A solution of sulfuric acid has a concentration of 0.0980 g/L. If the density of the acid is 1.84 g/mL, what is the concentration in ppm
A biochemist has 100 mL of a buffered solution at pH 7.3. The concentration of the...
A biochemist has 100 mL of a buffered solution at pH 7.3. The concentration of the buffer is 0.1 M, and the pKa of the buffer is 7.8. If the biochemist adds 80 mL of a 0.1 N KOH solution to the above buffered solution, what will be the final pH to the nearest tenth of a unit?
Describe the procedure you would follow to determine the concentration of Vitamin C in a sample...
Describe the procedure you would follow to determine the concentration of Vitamin C in a sample if the volume of DCPIP required to reach the endpoint was more than the 25-mL flask could hold. Note the titration must still be carried out in the flask. Be sure to include any calculations you would need to perform.
Question: Using the information and equations below determine the concentration of Vitamin C in an unknown...
Question: Using the information and equations below determine the concentration of Vitamin C in an unknown soft drink. Hints: In this experiment, the amount of potassium iodate determines the amount of iodine that is produced. In addition, the first part of the experiment requires the determination of the concentration of the thiosulphate solution. This is done by generating a known amount of iodine via the reaction between potassium iodide and a known amount of potassium iodate in an acidic medium....
Describe the procedure you would follow to determine the concentration of Vitamin C in a sample...
Describe the procedure you would follow to determine the concentration of Vitamin C in a sample if the volume of DCPIP required to reach the endpoint was more than the 25-mL flask could hold. Note the titration must still be carried out in the flask. Be sure to include any calculations you would need to perform.
Calculate the concentration of the standardized thiosulfate solution. The following are the steps and the concentration...
Calculate the concentration of the standardized thiosulfate solution. The following are the steps and the concentration of my KIO3 was 0.0114 and the weighed mass of Na2S2O3 was 1.719 g Weigh about 1.7 g Na2S2O3  5H2O, and transfer it to a 4 oz glass storage bottle. Add 100 mL (graduated cylinder) of room-temperature DI water, which has beenbubbled extensively with nitrogen, and which contains 100 mg /liter Na2CO3. Mix thoroughly and add 1 drop of chloroform to prevent bacterial...
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT