# Determine Total Hardness of Water

## EXPERIMENT NO. 04 (a)

OBJECT: Hardness of standard hard water is 1000 ppm. To determine the total hardness of given water sample using EDTA as an intermediate solution and Eriochrome Black-T as an indicator.

#### OBSERVATION TABLE:

[A] Titration between standard hard water (SHW) sample and EDTA solution

 S. No. Volume of standard hard water (SHW) (mL) Burette Reading (mL) Concordant Reading (X) (mL) Initial Final 1 20 0.0 9.2ml 9.2ml 2 20 0.0 3 20 0.0

[B] Titration between unknown hard water (UHW) and EDTA solution

 S. No. Volume of unknown hard water (UHW) (mL) Burette Reading (mL) Concordant Reading (Y) (mL) Initial         Final 1 20 0.0 19ml 19ml 2 20 0.0 3 20 0.0

CALCULATION:

[A]  Standardization of EDTA

Hardness of standard hard water (SHW) = 1000 ppm

So, 1000 mL of SHW contains = 1000 mg CaCO3

Thus,1 mL of SHW contains = 1000/1000 mg CaCO3 = 1mg CaCO3

9.2 mL EDTA consume = 20 mL SHW = 20 mg CaCO3

Hence, 1 mL EDTA is equivalent to = 20/9.2 mg CaCO3

#### [B]  Hardness of unknown hard water (UHW) sample

20 mL UHW consumes = 19 mL EDTA = 19×(20/9.2) mg CaCO3

Thus, 1 mL UHW = 19/20 x 20/9.2 mg CaCO3 = 19/9.2 mg CaCO3

Hence, 1000 mL of UHW = 19/9.2×1000 mg/L CaCO3

Total hardness = 2065.21 ppm

RESULT: Total hardness of given unknown hard water is 2065.21 ppm.

### EXPERIMENT NO. 04 (b)

#### OBSERVATION TABLE:

[A] Titration between standard hard water (SHW) and EDTA

 S. No. Volume of standard hard water (SHW) (mL) Burette Reading (mL) Concordant Reading (X) (mL) Initial Final 1 20 0.0 9.2ml 9.2ml 2 20 0.0 3 20 0.0

[B] Titration between unknown hard water (UHW) and standardized EDTA solution

 S. No. Volume of unknown hard water (UHW) (mL) Burette Reading (mL) Concordant Reading (Y) (mL) Initial         Final 1 20 0.0 19ml 19ml 2 20 0.0 3 20 0.0

[C] Titration between boiled hard water (BHW) and standardized EDTA solution

 S. No. Volume of boiled water (BHW) (mL) Burette Reading (mL) Concordant Reading (Z) (mL) Initial Final 1 20 0.0 14.1ml 14.1ml 2 20 0.0 3 20 0.0

CALCULATION:

[A] Standardization of EDTA

Hardness of standard hard water (SHW) = 1000 ppm

So, 1000 mL of SHW contains = 1000 mg CaCO3

Thus, 1 mL of SHW contains = 1000/1000 mg CaCO3 = 1mg CaCO3

9.2 mL EDTA consume = 20 mL SHW = 20 mg CaCO3

Hence, 1 mL EDTA is equivalent to = 20/9.2 mg CaCO3

#### [B] Hardness of unknown hard water (UHW) sample

20 mL UHW consumes = 19 mL EDTA = 190x 20/9.2 mg CaCO3

Thus, 1 mL UHW = Y/20 x 20/X mg CaCO3 = 19/9.2 mg CaCO3

Hence, 1000 mL of UHW = Y/X x 1000 mg/L CaCO3

Total hardness = 2065.21 ppm

[C] Hardness of boiled hard water (BHW) sample

20 mL BHW consumes = Z mL EDTA = 14.1 x 20/9.2 mg CaCO3

Thus, 1 mL BHW = Z/20 x 20/X mg CaCO3 = 14.1/9.2 mg CaCO3

Hence, 1000 mL of BHW = 14.1/9.2 x 1000 mg/L CaCO3

Permanent hardness = 1532.60 ppm

Temporary Hardness = Total Hardness-Permanent Hardness = 2065.21-1532.60

= 532.61 ppm

RESULT:

Hardness of given water sample is-

Total hardness = 2065.21ppm Permanent hardness =1532.60ppm Temporary hardness = 532.61ppm