Water Hardness Essay

1280 Words6 Pages
Compleximetric Determination of Water Hardness Water Hardness is a term used to describe the concentration of CaCO3 and MgCO3 in a body of water. The sum of the concentrations are called hardness index and is calculated as mg/L or ppm CaCO3. The amount of CaCO3 is determined by titrating the Ca2+ present in the sample. It is generally determined by titration of a water sample with EDTA. In the first part, preparation of 5 x 10-3 m EDTA titrant was done by dissolving approximately 0.47 grams of EDTA in 250 ml distilled water. A pinch of MgCl2 • 6H2O was added. The solution served as the stock titrant. In the second part, preparation of diluted EDTA titrant was done. We took 10.00 ml aliquot of the prepared titrant and placed it in a 100.0 ml volumetric flask to dilute. We shook it and this served as the diluted titrant. In the third part, an assigned group prepared the standard CaCO3 by adding drops of concentrated HCl in the weighed CaCO3 in a 250 ml beaker. It was left for evaporation and the residue was placed in a 500.0 ml volumetric flask to dilute. In the fourth part, we determined the exact concentration of EDTA by standardization. Lastly, we determined the hardness of the water. The diluted EDTA titrant was used for the titration of the sample. 10.00 ml of the sample was used instead of the 10.00 ml standard CaCO3. Water hardness is an expression for the sum of the calcium and magnesium cation concentration in a water sample. These cations form insoluble salts with soap, decreasing soap’s cleaning effectiveness. They also form hard water deposits in hot water heaters. The standard way to express water hardness is in ppm CaCO3 that has the formula weight of 100.1 g/mole. An excellent way to determine water hardness is to perform a compleximetric titration using a standard ethylenediaminetetraacetic acid (EDTA) solution. Due to steric

More about Water Hardness Essay

Open Document