Colourimetry

Question 1

What is the procedure for using a colourimeter?

Answer 1

• choose a suitable filter (complementary colour of the sample)
• zero the colourimeter with a pure solution (H2O)
• make up a series of solutions of the substance, of different known concentrations and measure the absorbance of each in the colourimeter.
• plot a graph with absorbance (Y) against concentration (X)
• measure the absorbance of the unknown solution and use the calibration curve to determine the concentration of the solution that the absorbance corresponds to.

Question 2

What type of ligand is most useful to use?

Answer 2

A ligand which provides a particularly strong colour.

Question 3

Why should you use a filter with the complementary colour to the colour of the solution?

Answer 3

This will give the biggest readings as these wavelengths are being absorbed most strongly.