Question

What is the degree of hardness of a sample of water containing 10.2 mg of mgso4?

Answer 1

Solution :

1 mol MgSO4=1molCaco3

2 mol MgSO4=2molCaco3

i.e 2×100gCaCO3

∴

Hardness of water = 220 ppm

Answer 2

The degree of hardness of water sample is 8.5 ppm

Explanation:

The hardness of water is the concentration of multivalent cations

1 kg of water = 10⁻³ m³ of water = 1 lt of water

Wt of MgSO₄ = 10.2 mg

Molecular weight of MgSO₄= 120

Now,

Gram equivalents of MgSO₄ = Gram equivalents of CaCO₃

Weight of MgSO₄/Equivalent Weight of MgSO₄= Weight of CaCO₃/Equivalent weight of CaCO₃

or, (10.2 × 10⁻³)/(120/2) = Weight of CaCO₃/(100/2)

or, 1.7 × 10⁻⁴ = Weight of CaCO₃/50

or, Weight of CaCO₃ = 50 x 1.7 × 10⁻⁴

                                   = 8.5 × 10⁻³ gram

                                   = 8.5 mg

Thus, the hardness as of CaCO3 = 8.5 mg/lt = 8.5 ppm

Therefore, the degree of hardness of water sample = 8.5

Hope this answer is helpful.

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