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Introduction

Hardness of water Background: water hardness results from the presence of calcium and magnesium ions in solution. Te more Ca 2+ and Mg2+ ions present, the harder the water is. Aim: to investigate the hardness of different water by using titration Hypothesis: the harder the water, the more volume of EDTA it will take to change the indicator. For this experiment, Contrex will need the largest volume of EDTA as it is a strong mineral water. Tap water will need the least volume of EDTA to change the color as it is not strong as mineral water. ...read more.

Middle

add 25cm3 of EDTA into a burette. 2. check for air bubbles and leaks 3. add 25cm3 of vittel into a conical flask 4. Add 2cm3 of pH 10 buffer solution into the conical flask. 5. Add 2 drops of Murexide indicator into the conical flask. 6. Open the tap of the burette. 7. Close the tap if the color change is observed. 8. Measure the volume of EDTA solution need ed to change the color of Murexide indicator. ...read more.

Conclusion

This is because it has the hightest concentration of Ca2+ and Mg2+ ions. The indicator will change color when all of the Ca+2 and Mg+2 ions have reacted. The reactions of the metal ions are: Ca+2 + EDTA-2 -----> CaEDTA Mg+2 + EDTA-2 -----> MgEDTA For vittel, less volume of 0.02mol EDTA solution is needed as it is less mineralized. Tap water needs the least volume of 0.02mol of EDTA solution because it is not highly mineralized. This is because too much calcium in water can lead to build up that clogs pipes and causes health issues so tap water is softened. ...read more.

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