top of page

Determining the Concentration of Copper (II) Sulfate Hydrate Solution

Yezi Cho




The concentration of an unknown solution of copper (II) sulfate hydrate was determined through interpolation of a graph showing the relationship between concentration of copper (II) sulfate hydrate solution and absorbance at 635 nm. Initially, certain concentrations of copper sulfate were created by diluting a stock solution. The color intensity of the solutions were measured using a colorimeter, each depending on the concentration of the solution. The copper complex solution is blue due to the presence of the ion [Cu(H2O)6]2+. Blue light is transmitted while orange light is absorbed, making the color appear blue.


The colorimeter determines the level of absorbance of light by measuring the amount of transmitted light and incident light. The colorimeter sends a certain wavelength of light through the sample solution in a cuvette (incident light) and measures how much of the light is able to pass through (transmitted light).


Figure 1. Colorimeter (“Beer Lambert Law | Transmittance & Absorbance | Edinburgh Instruments”)





Concentration (M)

Absorbance at 635 nm (μm)

Stock solution

0.5

1.118

Dilution 1

0.4

0.903

Dilution 2

0.3

0.706

Dilution 3

0.2

0.483

Dilution 4

0.1

0.242

Unknown 1

0.401

0.909

Unknown 2

0.255

0.593


Figure 2. Relationship between concentration of copper (II) sulfate hydrate solution and absorbance at 635 nm




Unknown 1: 0.405M

% Error = 0.988%


Unknown 2: 0.258M

% Error = 1.163%




The estimated concentrations of the unknown copper (II) sulfate hydrate solution each had a percent error (%) of 0.988 and 1.163. The error could be due to rinsing the cuvette using distilled water and not removing the water completely. This may have lowered the solution’s concentration and accordingly decreased the measured absorbance as the water made the solution more diluted.


Comments


bottom of page