Question

Find degree of hardness of water sample in terms of ppm of caco3 if sample contains 10^-3 M CaCl2 and 0.05M NaCl

Answer 1

Explanation:

Numerical Problems based on hardness of water:- 1. . Calculate the temporary and permanent hardness of water sample containing Mg(HCO3)2= 7.3mg/L, Ca(HCO3)2= 16.2mg/L, MgCl2= 9.5mg/L, CaSO4=13.6mg/L).

Answer 2

The degree of hardness of water sample is 100 ppm

Explanation:

The hardness of water is the concentration of multivalent cations

Therefore, in the given sample of water, the hardness will be only due to CaCl₂

Molarity of CaCl₂ = 0.001 M

i.e. in 1 litre, the moles of CaCl₂ = 0.001

Molecular weight of CaCl₂ = 111

Thus, the weight of CaCl₂ = 0.001 × 111 = 0.111 gram

Now,

Gram equivalents of CaCl₂ = Gram equivalents of CaCO₃

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

or, 0.111/(111/2) = Weight of CaCO₃/(100/2)

or, 2 x 10?³ = Weight of CaCO₃/50

or, Weight of CaCO₃ = 50 x 2 x 10?³

                                   = 0.1 gram

                                   = 100 mg

Thus, the hardness as of CaCO₃ = 100 mg/lt = 100 ppm

Therefore, the degree of hardness of water sample = 100

Hope this answer is helpful.

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