4.6a colorimetry Flashcards
When carrying out colorimetry, how would you choose an appropriate colour or wavelength filter?
choosing one that is complementary to the colour of the species being tested
- the colour being transmitted is the same as the filter colour
How does colorimetry work?
it uses the relationship between colour intensity of a solution and the concentration of the coloured species present
What is a colorimeter or a spectrophotometer used for?
to measure the absorbance of light of a series of standard solutions, and this data is used to plot a calibration graph
the absorbance of the species can then be tested and plotted against the calibration graph to find the concentration
How can the concentration of the solution being tested be determined?
from its absorbance and by referring to the calibration curve
What must the concentrations of the coloured species being tested do?
must lie in the straight line section of the calibration graph
What must the concentrations of the coloured species being tested do?
must lie in the straight line section of the calibration graph
How do you decide on appropriate concentrations for preparing a series of standard solutions?
choose a range of concentrations are likely to include the concentrations in your experiment
How would you use a blank in colorimetry?
fill a cuvette with water and press and hold the CAL button until the screen says CAL and then changes to a reading of 0.00 then release the CAL button
How would you prepare a calibration graph?
- prep standard solution
- make standards by serial dilution
- put the standards in cuvettes
- run standards in colorimeter
- plot graph of absorbance (y-axis) against concentration (x-axis)
What is a calibration graph used for?
used to determine the concentration of a sample of unknown concentration
