Question

 1.0 gm of CaCO3 was dissolved in HCl and the solution made up to 1000 ml with distilled water. 50 ml of the solution required 45 ml of EDTA solution for titration. 50 ml of hard water sample required 28 ml of EDTA and after boiling and filtering required 15 ml of EDTA solution. Calculate the hardness of water.​

Answer 1

The total hardness of the water sample is 622.16 ppm.

Given that;

The concentration of solution of HCl in water  = 1.0g of caco3/1000ml distilled water   = 1mg/ml

50 ml of solution requires 45 ml of EDTA, 1 ml of EDTA = 50/45 mg equivalent  hardness.

50 ml of hard water sample requires 28 ml of EDTA.

50 ml of the sample after boiling requires 15 ml EDTA.

To find;

The hardness of the water.​

Solution;

The hardness of sample is given by,

The hardness of the sample = 28 x 50/45 mgCaCo3 equivalent to 50ml a sample.

Hardness/litre of the sample = (28 x 50/45) x $\frac{1000}{50}$ = 622.16 ppm

After boiling the sample,

Permanent hardness of sample = (15 x 50/45) x $\frac{1000}{50}$ = 333.3 ppm

We know that,

Temporary Hardness = Total Hardness - Permanent hardness = 622.16 - 333.3 = 288.86 ppm

The total hardness of the water sample is 622.16 ppm.

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Answer 2

Answer:

Temporary Hardness = Total Hardness - Permanent hardness

Temporary Hardness = 312.5-208.3 = 104.2 ppm.

Explanation:

From the above question,

They have given :

Hardness of sample is given by,

Hardness of sample =  equivalent of 50ml sample.

Hardness/litre of the sample =   = 312.5 ppm.

After boiling the sample,

Permanent hardness of sample =  equivalent for 50 ml.

Permanent hardness/litre of sample =  = 208.3 ppm.

Temporary Hardness = Total Hardness - Permanent hardness

Temporary Hardness = 312.5-208.3 = 104.2 ppm.

The total hardness of the sample is 312.5 ppm.

The concentration of solution of HCl in water  =   = 500mgs in 500 ml of water = 1mg/ml

50 ml of solution requires 48 ml of EDTA, 1 ml of EDTA = 50/48mgs equivalent  hardness.

50 ml of hard water sample requires 15 ml of EDTA.

50 ml of the sample after boiling requires 10 ml EDTA.

Temporary Hardness = Total Hardness - Permanent hardness

Temporary Hardness = 312.5-208.3 = 104.2 ppm.

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