1.5 Post-Lab Questions 1. Explain why the wavelength of 530 nm was used to measu

Question

1.5 Post-Lab Questions 1. Explain why the wavelength of 530 nm was used to measure the absorbance of the complex? 2. if a solution obeys the Beer-Lambert Law, why is it better to plot the absorbance vs. concentration data for several concentrations, rahter than using only a single solution plus the origin to determine the straight line? 3. How did the concentration of aspirin in your tablet match the claims of the manufac- turer? 4. A solution of K2CrO, hs an absorbance of 0.395 in a 1.00-cm cell at a wavelength of 370 nm. The value of (molar absorptivity coefficient) is 4.84 Lm01-1-cm-1 for K2CrOs at that wavelength. What is the concentration of the solution? 1.6 Pre-Lab Questions nf glunse ancentration in blood serum is can be based on the

Explanation / Answer

Ans: 1 Most of the simple organic molecules (e.g, Benzene) absorbs the wavelength near to 200~400 nm. However, As molecular size increases, it also involves the overlaps of many electronic levels (orbital overlapping or bands overlapping). Which results in decrease in energy of excitation/emission/absorption. And hence as energy is inversly proportional to the wavelength. The wavelength increases. In case of complexes, presence of d electrons or conjugated/pi systems can observe in the same region. However, they do absorb near the 530 nm not at 530 nm.

Ans 2: As Beer-Lambert law suggest, the absorbance depends upon the wavelength, length of cell and analyte concentration. When we are deal with only one solution. It may face the limitations of Beer-Lambert law. On increasing the length of tube, concentration of analyte etc

a. Length can effect the passing of light (dielectric effects) which is directly related to increased concentration of analyte.

b. Increased concentration can cause the precipitation or coagulations etc. which might interfere the precision

c. Shift in thermodynamic equilibria of solution (again related to concentration)

Ans 3: The answer can be generalized to any other also.

However it involves many processes like

a. A set of clinical studies performed before on the substances (Here aspirin) which suggest the required dosage for type of diseases

b. For many years, studies has been done on the same drugs by experts like scientist and doctors regarding the usage.

c. The amount given produces or affects the other enzymes, blood vessels inside the body. Because every substances produced some biproducts which can cause interference with natural biological processes.

All these points are considered while preparing the exact concentrations and many experts are involved which certify the claim of manufacturer.

Ans 4: From Beer-Lambert Law

Absorbance = Molar absorptivity X cell length X concentration

0.395 = 4.84 L mol-1cm-1 X 1 cm X conc (c)

conc = 0.395 / (4.84) = 0.0816 mol L-1

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.