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