The estimation of hardness is based on complexometric titration. Hardness of water is determined by titrating with a standard solution of ethylene diamine tetra acetic acid (EDTA) which is a complexing agent. Since EDTA is insoluble in water, the disodium salt of EDTA is taken for this experiment.
How do you do EDTA titration?
Titration Procedure Titrate with EDTA from violet through wine-red to blue. It is recommended to experiment with a 5 mL aliquot to get an idea of the color and titre. The indicator color changes slowly, thus, the titrant must be added slowly near the endpoint with thorough stirring. Calculate the molarity of the EDTA.
Which indicator is used in EDTA method?
erichrome black T
In EDTA method is ethylene diamine tetra acetate is the compound used to remove the hardness. Explanation: The indicator used in the EDTA method is erichrome black T. The hardness causing ions like Ca++ and Mg++ forms the unstable complexes with reacting the erichrome black T.
How is EDTA concentration calculated?
Calculate the concentration of calcium ions in the hard water sample.
- Calculate the average titre of EDTA: average titre = (8.76 + 8.80 + 8.78) รท 3 = 8.78 mL = 8.78 x 10-3 L.
- Calculate the moles of EDTA in the average titre: moles(EDTA) = concentration (mol L-1) x volume (L) = 0.010 x 8.78 x 10-3 = 8.78 x 10-5 mol.
What methods are available for determination of hardness?
The methods that can be used to determine water hardness are titration with EDTA, atomic absorption spectroscopy and gravimetric analysis.
What is EDTA method?
The hardness of water can be determined by using EDTA method. EDTA is Ethylene diamine tetra acetic acid. It dissolves in water with great difficulty, but its disodium salt dissolve in water quickly & completely It is hexa dentate ligend. It binds the metal ions in water to give stable chelate complex.
Which buffer is used in EDTA titration?
pH 10 buffer is used in EDTA titration because in EDTA Y4- is predominant, and we want Y4- to react with the metal ions that are present in the titration solution. This can be achieved by using a pH 10 buffer.
How many chelating sites does EDTA offer?
This is EDTA acting as a hexadentate ligand or all six sites on the ETDA bind to the metal ion.
Which is the best method for hardness determination and why?
Hardness is most commonly measured by titration with an EDTA solution. A titration involves adding small amounts of a solution to a water sample until the sample changes color. You can titrate a sample for total hardness using a buret or test kit.
