Hardness of water is estimated simple titration with-Na[EDTA]Na2[EDTA]Na3[EDTA]Na4[EDTA]

The hardness of water is typically determined using a titration with Na2[EDTA]. Here are the steps:

1. Take a known volume of water sample in a conical flask.

2. Add buffer solution to the water sample to maintain the pH. The pH is usually adjusted to about 10.

3. Add a few drops of Eriochrome Black T indicator to the water sample. This will turn the solution wine red if hardness is present.

4. Titrate this solution with the Na2[EDTA] solution. During the titration, the EDTA molecules sequester the calcium and magnesium ions.

5. Continue the titration until the color changes from wine red to blue. This indicates that all the hardness causing ions have reacted with the EDTA.

6. Note down the volume of EDTA solution used. This can be used to calculate the hardness of the water.

The formula to calculate hardness is:

Hardness (as CaCO3) in mg/L = (Volume of EDTA solution in mL) x (EDTA concentration in mg/L) x (1000) / (Volume of water sample in mL)

Remember to always run a blank determination alongside your sample to correct for any errors.