A2-Level Transition Elements

  • Coloured solutions absorb specific wavelengths of visible light. The more concentrated a solution, the greater the intensity of light absorbed.

  • Colorimetry is used to find the concentration of a solution based upon the intensity of light (of a specific wavelength) it absorbs.

    • The amount of light that passes through the sample is detected and this gives an indication as to the amount of light absorbed by the sample.

    • A calibration curve is made using the absorbance’s of solutions of known concentrations.

    • The absorbance of the unknown solution is compared to the calibration curve and the concentration found. ​

QUICK NOTES

Colorimetry

 

The intensity of light absorbed by a solution is dependent on the concentration of the solution. The greater the concentration of a solution, the greater the intensity of wavelengths absorbed.  Colorimetry is a useful technique that is used to find the concentration of a solution. The intensity of light absorbed by a solution is measured, which can be used to find the concentration using a calibration curve.

 

Colorimeters measure the wavelengths of light absorbed or scattered by a substance, enabling graphs (spectra) to be formed that are unique to every substance. A colour filter is used to remove the wavelengths of light not absorbed by the solution.

 

 

 

The greater the concentration of solution, the greater the intensity of wavelengths absorbed by the solution (in this case orange light).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The intensity of absorption for the solution is measured for known concentrations.

 

 

 

 

 

The results are plotted on a graph and a line of best fit is drawn. This is called a calibration curve.

 

 

 

The results for the original solution with an unknown concentration are obtained and compared with the calibration curve and the concentration found.