Determining the total hardness in water using complexometric titration with EDTA tutorial suitable for chemistry students. Complexation Titration: Determination of Total Hardness of Water The use of EDTA as a complexometric titrant for metal ions has been investigated in the past . You will use EDTA complexometric titration to determine the hardness of a responsible for hardness, and total water hardness is defined as the sum of the.

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Determining Total Hardness in Water by Complexometric Titration

Please do not block ads on this website. Calcium stearate and magnesium stearate or soap scums makes it hard to lather but can be rinsed off easily Helmenstine, Slowly add the EDTA dropwise until the first permanent colour change that is, the solution goes blue and stays blue. The average total hardness of the sample is The use of EDTA as a complexometric titrant for metal ions has been investigated in the past few years Hamilton, et al, Calcium carbonate concentration expressed in parts per million are usually the criteria for the determination if a particular water sample is hard.

Take the test now! Seannekate, my lab partner was able to contribute effectively in proper handling of the instrument and other necessary calculations for the data. At the equivalence point of the titration: This may be due to the precipitation of the stearate ion, from the glycerol contained in the soap, when it reacts with either magnesium or calcium. The ionised form of EDTA is shown on the right. Add 2 drops of indicator such as Eriochromschwartz-T which will turn wine-red in the hardnesx water.


Accurately weigh out the required amount wster EDTA onto a watchglass. For example, to prepare mL of a 0.

Then, the total hardness of water was then determined to be To do so we can acidify the solution with hydrochloric acid, boil it, and then neutralize with ammonia. Total hardness refers to the combined hardness caused by bicarbonates, sulfates and chlorides of calcium and magnesium Hamilton, Help Center Find new research papers in: Slowly add the EDTA 1 mL at a time until you start to see indications of a colour change in the solution, that is, a spot of blue appears before disappearing.

Water Hardness and Alkalinity. EDTA dissolved in water forms a colourless solution. Fundamentals of Analytical Chemistry.

Introduction to Organic Chemistry; MacMillan: Use this volume of EDTA as a guide in repeating the titration. The precision is expressed in coefficient of variation that is in parts per thousand. Note the approximate endpoint of the titration. Perform calculations to determine the concentration of calcium and magnesium ions in the hard water. About us Feedback Determination of water total hardness by complexometric titration. Make sure the stopcock on the burette is closed!

Eriochromshwartz-T is wine-red in hard water, but turns sky blue in the presence of free EDTA ions in the solution. Experimenters are now able to learn the basics and techniques in this kind of titration. Use a clean, dry, spatula to transfer some of the EDTA from the watchglass to the funnel.

After that, the CaCl 2 solution was titrated with the EDTA solution until the color changed from wine red to pure blue. Complexometric titration is one of the best ways of measuring total water hardness. In general, there are many applications where ability to easily determine water hardness is very important. The abovementioned reactions and techniques can also be done for different applications in connection to the ability of EDTA and other complexing agents with metal ions.


Titrations that are based on complex formation are called complexometric titration. Click here to sign up. Water hardness is a measure of the amount of calcium and magnesium salts dissolved in water.

For the standardization, Use a small amount of water from a wash bottle filled with deionised water to wash the EDTA out of the funnel and into the flask. In addition with this, the water system in the laboratory should need treatment such as water softening.

Skip to main content. Use the rough titration above as a guide as to where the endpoint is. Calcium and magnesium ions are kept in solution with the aid of a weak complexing reagent such as the ammonia used in this example, or tartrate is also used.

Magnesium will be displaced by identical amount of calcium, and it will be titrated later, not changing final result. To maintain the pH at around 10, a buffer soluton is required for the titration.

Determining Total Hardness in Water Chemistry Tutorial

Keep swirling the conical flask during the titration to mix the contents. Lerona, Paul Gabriel E. This could have been the reason why lathering of the soap is wateg little hard but rinsing it off is easy.