Hardness of Water

INTRODUCTION:

WHAT IS HARDNESS OF WATER:

It is when water passes through or over deposit such as limestone; the level of Ca²⁻and Mg²⁺and HCO₃ ions present in the water can greatly increase and cause the water to be classified as hard water. This term results from the fact that cation and magnesium ions in water combine with soap molecules, making it hard to get suds. High level of water ion such as Ca²⁻ and Mg²⁺ can cause scaly deposits in plumbing appliances & boilers.

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These two ions also combine chemically with soap molecules resulting in decreased cleansing. The American water works Association indicates that the ideal quality water should not contain more than 80mg/l of total hardness as CaCO₃. High levels of total hardness are not considered a health concern. There are two types of Hardness:

Temporary hardness: this is due to the presence of bicorbonates of calcium and magnesium. It can be easily removed by boiling. Permanent hardness: this is due to the presence of chlorides & sulphate of calcium & magnesium. This type of hardness cannot be removed by boiling.

MOTIVATION

I was bothered that the water in Ilara community doesn’t combine easily with soap leading to excessive consumption of WATER.

ENVIRONMENTAL SIGNIFICANCE:

Scales are formed as inner coating of the pipelines prevents corrosion Absolute soft waters are corrosive and dissolve metals

More causes of cardio vascular diseases are reported in soft water areas Hard water is useful to growth of children due to the presence of calcium Hard water cause excessive consumption of soap used for cleaning purpose, sodium soaps react with multivalent metallic cations to form a precipitate, thereby lose their surfactant properties. Lathering doesn’t take place until all hardness ions precipitate out.

APPARATUS

• Conical Flask {250ml}
• Burette with retort stand
• Beaker
• Wash bottles
• Standard flask
• Pipettes

REAGENTS

• Ammonium chloride
• Ammonium hydroxide
• Ilara-Mokin water {H₂O}
• Magnesium sulphate
• Erichrome black T
• EDTA (Disodium salt).

PREPARATION OF REAGENTS

Standard solution of EDTA

The usual reagent is the disodium salt, which is a dehydrate, Mr=372.24; it is available in sufficiently pure form to be used as a primary standard for most purposes. If necessary, it may be dried at 80° for four days to remove a small percentage of water that may have been absorbed. The solution should be stored in plastic containers rather than glass bottles. The solution is stable but if stored in glass bottles (particularly if the glass is new), the concentration of a dilute solution will decrease appreciably with time as metal ions are extracted out of the glass. To prepare 2 1 of the reagent, dissolve 7.44g of the salt in enough deionized water to make exactly 2 1 of solution. 2. Buffer solution(pH 10)

Add 17.5g of ammonium chloride to 142cm³ of ammonium chloride to 142cm³ of 0.88 ammonia solution and make up to 250cm³ with deionized water. 3. Eriochrome Black T indicator

This indicator can be purchased as a powder. The solid is hygroscopic, and so must be stored in a tightly stoppered container.

EXPERIMENTAL PROCEDURE (testing of the Ilara-mokin water)
We Pipetted 200ml of the water sample and transfer it to a clean 250ml conical flask. We Added 2ml of Ammonia buffer solution to the water sample so that the pH will be maintained between 9 & 10. We added few drops of EBT indicator to the conical flask and the sample turns to wine red in color. Before we started the titration; we rinsed the burette with few ml of EDTA then Filled the burette with 0.02m EDTA solution & adjusted to zero then fixed it in retort stand. We titrated the sample against the EDTA solution in the burette till all calcium and magnesium ions present in the sample reacted with the EDTA.

The appearance of blue color indicated that all Ca and Mg ions were complex with EDTA and forms a metal EDTA complex. i.e. the end point of the titration We Noted down the burette reading and repeated titration two more times.

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