Question

2 moles of cacl2 is present in 18 kg of water calculate its degree of hardness

Answer 1

SAMPLE OF HARD WATER CONTAINS 1Mg CaCl2 AND 1 Mg MgCl2 PER LITRE . CALCULATE THE HARDNESS OF WATER IN TERMS OF CaCO3 PRESENT IN PER 106PARTS OF WATER.

PLEASE TELL EACH STEP HOW TO CALCULATE HARDNESS

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Answer 2

The degree of Hardness is 1111.11 ppm

Explanation:

Moles of CaCl₂ = 2

Molecular weight of CaCl₂ = 111

Therefore, weight of CaCl₂ = 111 × 2 = 222 gm

Mass of water = 18 kg

We know that density of water = 1000 kg/m³

Therefore, volume of water = Mass /Density

                                              = 18/1000 m³

                                              = 18 × 10⁻³ m³

                                              = 18 litre

Now,

Gram equivalent of CaCl₂ = Gram equivalent of CaCO₃

Weight of CaCl₂/Equivalent weight of CaCl₂ = Weight of CaCO₃/Equivalent weight of CaCO₃

222/(111/2) = Weight of CaCO₃/(100/2)     (∵ Equivalent weight = Molecular weight/Valency)

or, 4 = Weight of CaCO₃/50

or, Weight of CaCO₃ = 200 g

Therefore, in 18 litre, hardness as CaCO₃ = 200g

In 1 litre hardness as CaCO₃ = 200/18 g/L = 11.11 g/L

                                                                      = 11111.11 mg/L

                                                                       = 11111.11 ppm

Thus, the degree of hardness = 1111.11 ppm

Hope this answer is helpful.

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