Tuesday, August 31, 2010

ANSWERS to Review Questions- Spectrophotometry

1. State Beer's law

The concentration of the solution is directly proportional to the absorbance and inversely proportional to the transmitted light.

2. What is the relationship between the intensity of color of a solution to its concentration?

The intensity of color of a solution is directly proportional to its concentration.

3. What is the formula in solving the Cu?

Cu = Au X Cs/ As

Where: Cu -Concentration of the unknown
Au -Absorbance of the unknown
Cs -Concentration of the standard
As -Absorbance of standard

4. What are the other methods in computing for your unknown concentration?

a. Ratio of standard to known, using the formula in No. 3
b. Absorptivity value
c. Standard curve

5. Give the types of wavelength and the ranges by which they occur.

Ultraviolet (UV) - Below 350 nm
Visible - 350 to 800 nm
Infrared (IR) - above 800 nm

6. List the specific colors for each wavelength.

Blue - 475 nm
Green - 510 nm
Yellow - 570 nm

7. List and describe briefly the basic components of the spectrophotometer.

Light source- provides a continuous source of light.

Entrance slit - prevents entry of extraneous light.

Monochromator - selects the wavelength of choice in reading the unknown.

Exit slit - purifies and intensifies the light entering the cuvette.

Cuvette - contains the unknown solution.

Detector - detects the light absorbed or transmitted and converts it to a reading.

Readout device or digital display window - reflects the readings or concentration of the unknown solution.

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