What does EDTA test for water hardness?
EDTA can form four or six coordination bonds with a metal ion. Total hardness is due to the presence of bicarbonates, chlorides and sulphates of calcium and magnesium ions. The total hardness of water is estimated by titrating the water sample against EDTA using Eriochrome Black-T (EBT) indicator.
What happens when EDTA is added to hard water?
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.
Does EDTA add hardness to a water sample?
It can also be used to determine the total hardness of fresh water provided the solutions used are diluted. The combined concentration of calcium and magnesium ions is considered to be the measure of water hardness. The method uses a very large molecule called EDTA which forms a complex with calcium and magnesium ions.
Why is EDTA used to determine the hardness of water?
Hardness in water is due to the presence of dissolved salts of calcium and magnesium. 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.
Is EDTA acidic or basic?
EDTA is a Weak Acid. EDTA, ethylenediaminetetraacetic acid, has four groups of carboxyls and two groups of amines that can serve as donors of electron pairs, or Lewis bases.
Why do we add buffer solution during titration of hard water against EDTA solution?
A buffer solution is used in EDTA titration because it resists the change in pH. This is because all the reactions between the metal ions and EDTA are pH-dependent.
What is the ideal level of water hardness for sea water?
Total hardness as 100 mg/L provides good control over corrosion and is the usually acceptable limit. TH is usually classified (EPA, 1986) as soft (0–60 mg/L), moderately hard (60–120 mg/L), hard (120–180 mg/L) and very hard (>180 mg/L).
What is principle of 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. Hence it is called as complexometric titration method.
What is EDTA and its formula?
C10H16N2O8
Ethylenediaminetetraacetic acid/Formula
Why EDTA is a weak acid?
EDTA is a Weak Acid. EDTA, ethylenediaminetetraacetic acid, has four groups of carboxyls and two groups of amines that can serve as donors of electron pairs, or Lewis bases. Since EDTA is insoluble in water, this experiment uses the disodium salt of EDTA.
Does EDTA act as a buffer?
EDTA forms complexes with the calcium and magnesium ions that are red. Since both EDTA and the indicator are themselves weak acids, a buffer solution , which is able to maintain a fairly constant pH even when acids and bases are added, is used.
How is EDTA used to determine the hardness of water?
Complexometric titrations are titrations that can be used to discover the hardness of water or to discover metal ions in a solution. Ethylenediaminetetraacetic acid, also known as EDTA, is commonly used in complexometric titrations.
How is the hardness of a water sample determined?
Determination of Water Hardness. In this experiment, the hardness of an unknown water sample will be determined. The calcium in the water will be measured by performing a titration with EDTA. Eriochrome Black T will be used as an indicator. Standardization of EDTA will be performed first and then the determination of calcium concentration.
How to prepare disodium salt of EDTA ( dico3 )?
Disodium salt of EDTA or disodium EDTA dihydrate Calcium carbonate primary standard (CaCO3) Sodium hydroxide solution, 3 M. Prepare from a 50% wt/wt NaOH solution. Sodium sulfide solution (5% wt /vol) in water (freshly prepared by Lab Services).
How does EDTA work in a titration reaction?
In a titration, EDTA, a stronger complexing agent than the indicator, displaces the indicator form the metal ion allowing the indicator to return (through shades of violet) to a pure blue color, indicating the end of the reaction.