How is water hardness determined by titration EDTA?

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. EDTA can form four or six coordination bonds with a metal ion.

What is the role of EDTA solution in water hardness determination titration?

In the determination of water hardness, ethylene- diaminetetraacetic acid (EDTA) is used as the titrant that complexes Ca2+ and Mg2+ ions. This color change signals the end point, as it takes place when the EDTA, after complexing all of the unbound Ca2+ and Mg2+ ions, removes the Mg2+ ion bound to the indicator.

How do you standardize EDTA solution?

Preparation and Standardization of 0.1 M Disodium Edetate (EDTA)

  1. Take about 100 ml of water in a cleaned and dried 1000 ml volumetric flask.
  2. Add about 37.2 gm of Disodium Edetate with continues stirring.
  3. Add more about 700 ml of water mix.
  4. Make up the volume 1000 ml with water.

How do you calculate EDTA concentration?

Calculate the concentration of calcium ions in the hard water sample.

  1. 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.
  2. 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.

How do you calculate total water hardness?

The amount of hardness is expressed in milligrams per litre (mg/L) or grains per gallon (gpg) as calcium carbonate. Hardness is calculated from the equation Hardness = 2.497 (Ca) + 4.118 (Mg).

How do you determine the hardness of water?

Water hardness can be easily measured using a simple soap test kit that will measure in “grains of hardness” (a little bottle with a line marked on it which you fill to the line with water, add a drop of soap, and shake to look for suds. More drops of soap – more degrees of hardness).

How does EDTA help you determine metal ions in water?

The unusual property of EDTA is its ability to chelate or complex metal ions in 1:1 metal-to-EDTA complexes. The fully deprotonated form (all acidic hydrogens removed) of EDTA binds to the metal ion. Metal analysis can be done by titration with EDTA and the use of a metal ion indicator.

How does EDTA titration work?

EDTA is short for ethylenediaminetetraacetic acid. For the titration, the sample solution containing the calcium and magnesium ions is reacted with an excess of EDTA. The indicator is added and remains blue as all the Ca2+ and Mg2+ ions present are complexed with the EDTA.

What is EDTA in titration?

How is EDTA solution prepared for titration?

EDTA Solution Preparation Weigh out approximately 2 g of reagent grade disodium EDTA into a 250 mL beaker. Add 0.05 g magnesium chloride hexahydrate, three pellets of NaOH and add about 200 mL of distilled water to dissolve. The EDTA will dissolve slowly over a period of a half an hour.

What is the total hardness of water?

Total hardness is the sum of the calcium and magnesium concentrations, both expressed as calcium carbonate, in milligrams per liter (mg/L). You can determine your water’s hardness based on these concentrations of calcium carbonate: below 75 mg/L – is generally considered soft. 76 to 150 mg/L – moderately hard.

How is hardness of TDS calculated in water?

However, for estimation purposes, the water hardness can be roughly calculated by dividing the ppm (parts per million) measurement of the TDS by 10 giving a hardness value with an error of only 2-3 French degrees. TDS measurements can also be derived from relative conductivity measurement.

How is the hardness of water determined by EDTA?

EDTA Titration Calculations The hardness of water is due in part to the presence of Ca2+ions in water. Theconcentration of Ca2+ions is usually expressed as ppm CaCO3in the water sample. Thisis equivalent to 1 gram of CaCO3in 106grams of sample. In the lab 1 ppm CaCO3isexpressed as 1 mg CaCO3per 1 Liter of sample or ppm is mg CaCO3per L of sample.

What is the end point of EDTA titration?

In a titration to establish the concentration of a metal ion, the EDTA that is added combines quantitatively with the cation to form the complex. The end point occurs when essentially all of the cation has reacted. In this experiment you will standardize a solution of EDTA by titration against a standard solution made from calcium carbonate, CaCO3.

How is the hardness of water determined by titration?

Water hardness can be readily determined by titration with the chelating agent EDTA (ethylenediaminetetraacetic acid). This reagent is a weak acid that can lose four protons on complete neutralization; its structural formula is below.

Which is the best way to measure the hardness of water?

Complexometric titration is one of the best ways of measuring total water hardness. At pH around 10 EDTA easily reacts with both calcium and magnesium in the same molar ratio (1:1). Stability constant of calcium complex is a little bit higher, so calcium reacts first, magnesium later.