Question

A water sample contains 200 mg of caso4 per litre calculate the hardness in terms of caco3 equivalent in milligram per litre PPM

Answer 1

Answer: 147 mg/L

Explanation:

Hardness of water is measured in terms of $CaCO_3$ equivalents.

Given:

Hardness of water = 200 mg/l  of $CaSO_4$

$CaCO_3$ equivalents= $\frac{\text {given mass of hardness causing impurity}}{\text {Molecular mass of hardness causing impurity}}\times {\text {Molecular mass of } CaCO_3}$

given mass of hardness causing impurity i.e $CaSO_4$ = 200 mg/L

Molecular mass of hardness causing impurity i.e $CaSO_4$ = 136 g/mol

Molecular mass of $CaCO_3$ = 100 g/mol

Putting the values we get:

$CaCO_3 equivalents=\frac{200mg/L}{136g/mol}\times 100g/mol=147mg/L$

Thus the hardness in terms of  $CaCO_3$ equivalent in milligram per litre is 147.

Answer 2

The degree of hardness of water sample is 147 ppm

Explanation:

The hardness of water is the concentration of multivalent cations

In 1 lit of water

Wt of CaSO₄ = 200 mg = 0.2 gram

Molecular weight of CaSO₄= 136

Valency = 2

We know that

Equivalent Weight = Molecular Weight/Valency

Now,

Gram equivalents of CaSO₄ = Gram equivalents of CaCO₃

Weight of CaSO₄/Equivalent Weight of CaSO₄= Weight of CaCO₃/Equivalent weight of CaCO₃

or, 0.2/(136/2) = Weight of CaCO₃/(100/2)

or, 0.2/68 = Weight of CaCO₃/50

or, Weight of CaCO₃ = (0.2/68) × 50

                                   = 0.147 gram

                                   = 147 mg

Thus, the hardness as of CaCO₃ = 147 mg/lt = 147 ppm

Therefore, the degree of hardness of water sample = 147

Hope this answer is helpful.

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