Question

A 100 ml sample of water require 20 ml of 0.02 M EDTA for titration using EBT as indicator. 100 ml of same water sample boiled and precipitate removed by filtration, the filtrate requires 9 ml of 0.02 M EDTA for titration. Calculate the total hardness, permanent hardness and temporary hardness of water sample.

Answer 1

Explanation:

100 mL sample of hard water is titrated with 500 " mL of " 0.001 M EDTA solution at `pH=10`, using eriochrome black-T indicator to reach equivalence point. An equal another amount of hard water sample is boiled for 30 min. After filtration and cooling, the same sample is titrated with 200 " mL of " 0.011 M EDTA solution at `pH=10` using Mg-EDTA complex solution and erichrome black-T indicator to reach equivalence point. <br> (i). Calculate the total hardness of water sample (temporary`+`permanent) in ppm of `CaCO_3`. <br> (ii). Calculate the permanent hardness of water sample in ppm of `CaCO_3`. <br> (iii). Calculate the temporary hardness of water sample in ppm of `CaCO_3`