Serial Dilution Activity

1
Serial Dilution Activity

• Using a pipet
• Simulated Acid
• Red nitric acid
• Yellow sulfuric acid
• Blue hydrochloric acid

2
Spec-20 Instrument
Wavelength control knob
Light control knob
Amplifier control knob
Sample holder cover
3
Spec-20 Absorbance
Insert Photograph Spec-20
100 Absorbance 0 Transmittance
Absorbance
0 Absorbance 100 Transmittance
l (wavelength)
4
Schematic representation of a spectrophotometer
I
Io
Detector
Monochromator
Meter
Light Source (1)
Sample cell (3)
(2)
(4)
(5)
A spectrophotometer is an instrument that
measures the fraction (I/Io) of an incident beam
of light (Io) which is transmitted (I) by a
sample at a particular wavelength.
For a given substance, the amount of light
absorbed depends on a) the concentration
b) the cell or path length c) the
wavelength of light and d) the solvent.
5
Absorbance of Chlorophyll
1.5
1.2
0.9
Absorbance
0.6
0.3
0.0
300
400
500
600
700
800
Wavelength (nm)
6
Amount absorbed
663 nm
400
500
600
700
Wavelength (nm)
Kelter, Carr, Scott, , Chemistry A World of
Choices 1999, page 480
7
Calibration Curve
(fixed wavelength)
100 Absorbance 0 Transmittance
out of linear range (too concentrated)
?
Absorbance
0 Absorbance 100 Transmittance
x 2
Concentration
Dilute sample with water 5050. Run sample, read
concentration.
8
Dilution of Solutions
Dilution of Solutions  Dilution of Solutions
Dilution of Solutions  Dilution of Solutions
Keys
http//www.unit5.org/chemistry/Solutions.html