4. Suppose a solution was too concentrated for an accurate reading with the colo

Question

4. Suppose a solution was too concentrated for an accurate reading with the colorimeter. The concentrated solution was diluted by placing 1.00 mL of the concentrated solution in 4.00 mL of water. The solution was then placed in the spectrophotometer and an absorbance was obtained and after a few calculations the molar concentration was calculated to be 3.5 x 10 M. What was the concentration of the original solution before creating the stock solution by dilution? 5. The spectrophotometer really measures the percent of light that is transmitted through the solution. The instrument then converts %T (transmittance) into absorbance by using the equation you determined in the prelab section. If the absorbance of a sample is 0.85, what is the percent of light transmitted through the colored sample at this collected wavelength?

Explanation / Answer

4)

concentration solution volume V1 = 1.00 mL

final volume V2 = 5 mL

concentration C2 = 3.5 x 10^-6 M

concentration C1 = ??

C1 V1 = C2 V2

C1 x 1.00 = 3.5 x 10^-6 x 5

C1 = 1.75x 10^-5 M

concentration of original solution = 1.75 x 10^-5 M

5)

Absorbance = - log T

0.85 = - log T

T = 0.14

Transimittance = 14.1 %

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