Exp 4
Chapter
UALR
Dr. Robert Belford




Question 1
A substance has a molar extinction coefficient of 2.4x104cm-1M-1 and an absorbance of 0.10 What is the concentration of this substance in a cuvette with a 1.0 cm path length?
(A)  4.2x10-5
(B)  4.2x10-6
(C)  4.2x106
(D)  none of the above
 
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Question 2
A substance has a molar extinction coefficient of 2.4x104cm-1M-1 and an absorbance of 0.10 What is the concentration of this substance in a cuvette with a 1.0 mm path length?
(A)  4.2x10-5
(B)  4.2x105
(C)  4.2x10-6
(D)  none of the above
 
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Question 3
What is the absorbance of a 3.5x10-4 M solution in a 1.0 cm cell if the extinction coefficent is 3.82x103cm-1M-1?
(A)  13
(B)  1.3
(C)  .13
(D)  none of the above
 
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Question 4
What is the extinction coefficient if a 2.4x10-5M solution at 489 nm has an absorbance of 0.86 in a 1.0 mm cuvette.
(A)  3.6x10-5cm-1M-1
(B)  3.6x104cm-1M-1
(C)  3.6x10-4cm-1M-1
(D)  none of the above
 
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Question 5
A solution of an unknown chromophore with an extinction coefficient of 2.4x104cm-1M-1 at 489 nm has an absorbance of 2.1 in a 1.0 cm cuvette when measured in a spectrometer with a valid absorbance range of 0.05 to 1.00. The absorbance drops to 1.3 when you take 10.0 ml of the solution and dilute to 100.0 ml. This is still too high and so you take 10.0 mL of the diluted solution and dilute it to 100.0 mL. The absorbance is now 0.80. What is the concentration of this diluted solution.
(A)  3.3x10-4M
(B)  3.3x104M
(C)  3.3x10-5M
(D)  none of the above
 
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Question 6
What was the absorbance of the original solution in problem 5 which had an absorbance of 2.1
(A)  3.3x10-4M
(B)  3.3x10-3M
(C)  3.3x10-7M
(D)  none of the above
 
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