Estimation of Hardness of Water
Water hardness primarily arises from the presence of divalent metal ions, particularly calcium (Ca²⁺) and magnesium (Mg²⁺). To estimate the hardness of water, titration methods using specific chelating agents are employed.
Choice of Chelating Agent
Among the options provided, a. Mg(EDTA) and b. Na2(EDTA) are the most relevant for estimating water hardness.
Why Na2(EDTA)?
- Stability: Sodium disodium ethylenediaminetetraacetic acid (Na2(EDTA)) forms stable complexes with metal ions, especially Ca²⁺ and Mg²⁺, making it a preferred choice for titration.
- Versatility: It can effectively chelate various metal ions, allowing for a comprehensive assessment of water hardness.
- pH Control: The titration with Na2(EDTA) can be performed in a buffered solution, ensuring the pH remains conducive for complex formation.
Comparison with Other Options
- Mg(EDTA): While it can also be used, it is less common as a primary titrant for hardness estimation because it primarily targets magnesium ions.
- Co(EDTA) and Fe(EDTA): These forms are not typically used for hardness determination. They are more suited for specific metal ion analysis rather than general hardness.
Conclusion
In summary, Na2(EDTA) is the most suitable agent for the titration method used to estimate water hardness due to its stability, effectiveness, and versatility in binding divalent cations.