SPECTROPHOTOMETER ANALYSISDamian Ulrich and Sierra Werley

WHAT IS A SPECTROPHOTOMETER?

• An instrument that, when combined with a colorimeter in the lab, measures the amount of absorbance and transmittance a solution allows.

• The colorimeter is the device that allows the measurements to occur.

Colorimeter

Spectrophotometer

WHAT IS ABSORBANCE?• A measure of the capacity of a substance to absorb light of a specified

wavelength.• Different colors of light rays have different wavelengths.

WHAT IS TRANSMITTANCE?• The ratio of the light energy falling on a body to that transmitted through

it.

WHAT TO DO• You will be given concentration• Use the spectrophotometer to find absorbance or transmittance• Use a formula to find transmittance or absorbance (respectively)• The formula is:

• A=2-Log(%T)• A= absorbance• %T= percent transmittance (T*100)

WRITE THIS

DOWN

EXAMPLE• Given: Concentration of CuSO4 is .12M• Spectrophotometer shows the %T is 23.2• Find the absorbance of the CuSO4 in this situation.

• A= 2-log(%T)• A= 2-log(23.2)• A= 0.635 Au

QUIZ: QUESTION 1• Using a spectrophotometer, you find that the transmittance of a solution

is 9.9% at a concentration of 0.20M. Find the absorbance of the solution.

A. 0.98 Au

B. 1.01 Au

C. 0.50 Au

D. 0.28 Au

QUIZ: QUESTION 2• Using a spectrophotometer, you find the absorbance to be 1.38Au of a

solution with a concentration of 0.28M. Calculate the percent transmittance of the solution.

A. 4.8

B. 3.6

C. 4.1

D. 10.3

QUIZ: QUESTION 3• Using a spectrophotometer, you find the absorbance to be 1.73Au of a

solution with a concentration of 0.36M. Calculate the percent transmittance of the solution.

A. 1.9

B. 0.23

C. 5.7

D. 3.2

QUIZ: QUESTION 4• Using a spectrophotometer, you find that the transmittance of a solution

is 1.2% at a concentration of 0.40M. Find the absorbance of the solution.

A. 1.00 Au

B. 1.93 Au

C. 2.57 Au

D. 16.23 Au

QUIZ: QUESTION 5• You find the percent transition of an unknown solution to be 55.5%. Use

the equation to find the absorbance of the same solution.

A. 5.67 Au

B. 1.34 Au

C. 0.016 Au

D. 0.259 Au

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WORKS CITED• Thanks to Mr. Wolfe’s notes, the “Beer’s Law Lab” that came from

Investigating Chemistry through Inquiry, and Google for definitions, this tutorial was able to be created.