The hardness of water is estimated by
(a)conductivity method
(b)EDTA method
(c)titrimetric method
(d)distillation method

Options

A. conductivity method
B. EDTA method
C. titrimetric method
D. distillation method

Explanation

To determine the hardness of water, we can analyze the methods provided in the question. Let's go through the options step by step:

1. **Understanding Water Hardness**: Water hardness is primarily due to the presence of dissolved minerals, mainly calcium (Ca²⁺) and magnesium (Mg²⁺) ions.

2. **Evaluating the Methods**:
- **(a) Conductivity Method**: This method measures the electrical conductivity of water, which can indicate the presence of ions but does not specifically quantify hardness.
- **(b) EDTA Method**: The EDTA (ethylene diamine tetra acetic acid) method is a complexometric titration technique specifically designed to measure the concentration of calcium and magnesium ions in water. EDTA forms stable complexes with these ions, allowing for accurate determination of hardness.
- **(c) Titrimetric Method**: This is a broad category that includes various titration methods, including the EDTA method. However, it does not specify the use of EDTA for hardness determination.
- **(d) Distillation Method**: This method is used for purifying water and does not measure hardness directly.

3. **Conclusion**: The most accurate and specific method for estimating the hardness of water is the EDTA method, as it directly targets the ions responsible for hardness.

**Final Answer**: (b) EDTA method