4 Spectrophotometry and Beer\'s Law Time MTWR 1. Write the mathematical expressi

Question

4 Spectrophotometry and Beer's Law Time MTWR 1. Write the mathematical expression for Beer's law and explain each symbol in the expression. Use Figure 4.2 to estimate the approximate wavelength of maximum absorption for an aque- ous solution of each of the following: 2. a. Blood nm b. Carotene (the pigment that gives carrots their color) 3, Fill in the following for the correspondence between % transmittance and absorbance: 100.0 % T = absorbance 1.00 absorbance = % T 63.0 % T> ___ absorbance 0.34 absorbance = %T

Explanation / Answer

1 .mathematical expression for Beer's Law is :

A = lc

where A is absorbance.
is the molar absorbtivity ( units of L /(mol*cm) ).
l is the path length of the sample. ( generally in cm).
c is the concentration of the compound in solution, (expressed in mol /L).

2. figure not given

3. i) 0 absorbance

ii) .37 absorbance

iii) 0% T

iv) 66% T

4. according to question,

%T = 41.7%

=> A = (100 - 41.7)/100 = 0.583

l = 1cm

= 73.8 L/mole-cm

by beer's law

A =lc

=> c=A/l

c = 0.583/(73.8 * 1)

c = 7.899 * 10-3 mol / L

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