Lab Experiment

1
Lab Experiment 3

• Quantitative Analysis
• Spectrophotometry

2
Types of Analysis

• Qualitative analysis tells what is in the
  sample
• Presence or absence of chemical
• Presence or absence of organisms
• Quantitative analysis tells how much is in the
  sample
• Concentration of chemical
• Number of organisms per unit area or volume

3
Concentration

• (Amount of substance) / (Volume of solution)
• Examples
• grams / liter ( mg / ml)
• Other examples mg/l g/ml moles/l

4
Electromagnetic Spectrum

• Color based on light reflected (bounced back)
  or transmitted (passed through) other
  wavelengths are absorbed
• Wavelength
• measured in nm (10-9 m)
• has energy associated with it shorter
  wavelengths have more energy
• short to long gamma rays, x-rays, ultraviolet,
  visible light (400-700 nm), infrared, microwave,
  radio waves

5
Spectrophotometry

• Method of determining concentration of substance
  in a solution
• Absorbance how much light is absorbed by the
  substance in solution
• Wavelength each substance absorbs light of a
  particular wavelength best
• Concentration the more material in solution,
  the greater the absorbance
• Transmittance the amount of light that gets
  through
• Blank contains everything except the substance
  whose absorbance (and, thus, concentration) you
  want to determine
• transmittance is 100 when the blank is in place
• e.g., testing protein in dye and water blank has
  dye and water

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Standard Curve

• Determined based on absorbance of solutions with
  known concentration of substance
• Method
• Prepare solutions with known concentrations
• Measure absorbance of solutions
• Graph data
• Draw line of best fit

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Terms

• Accuracy how close the measurements are to
  reality
• Precision how close the measurements of a
  single concentration are to each other

8
Activities

• Determine the color of specific wavelengths
• Determine the wavelength of maximum absorbance
  for bromophenol blue
• Graph Connect the dots
• Prepare solutions of known concentration
• Determine the absorbance for solutions of known
  concentration
• Graph standard curve line of best fit
• Use the standard curve to determine the
  concentration of dye in an unknown solution

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Short Lab Report

• Pg. 47 relating lambda (?) to color
• Pg. 47 maximum absorbance for dye
• Graph
• Pg. 48 data for standard curve
• Graph
• BONUS calculate the slope of the line
• Pg. 49 conclusions

10
Metric Conversion

• The respiration chamber used in the experiment
  was 50.0 cm long by 30.0 cm wide by 30.0 cm high.
  (2 points)
•  Convert the chamber measurements (currently in
  cm) to meters
• ___ m long by ___ m wide by ___ m high

11
Dosage Bonus

• A certain drug is available in a liquid
  suspension of 25 g of drug per deciliter (25
  g/dl).
• A patient is supposed to receive 2.5 g of the
  drug.
• How many ml of the drug should she be given?