Question

50 ml of a water sample requires 12.7 of 0.02 M EDTA during titration. Calculate total hardness of the water.

Answer 1

EDTA can form four or six coordination bonds with a metal ion. Total hardness is due to the presence of bicarbonates, chlorides and sulphates of calcium and magnesium ions. The total hardness of water is estimated by titrating the water sample against EDTA using Eriochrome Black-T (EBT) indicator.

Answer 2

The total hardness of the water is calculated as $254 ppm$

Explanation:

• Given Volume of hard water sample used = 50 ml
• Volume of 0.02M EDTA solution consumed for titrating = 12.7 ml
• We have to find out the Total hardness of water
• Titration is done with the hard water sample using EDTA as the standard solution and the indicator will be Eriochrome black T.
• Let, Volume of water sample used = X
• Volume of 0.02M EDTA solution consumed = Y

Total Hardness =  $\frac{X}{Y}$ × 1000

= $\frac{12.7}{50}$×$1000$

$=254 ppm$

• The total hardness of the water is calculated as $254 ppm$