Question

(1) 100 g of hard water contains 0.00475 g MgCly. What is the hardness of water in ppm?
50 ppm
5 ppin
500 ppm
475 ppini​

Answer 1

Answer:

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Explanation:

Total hardness= Ca hardness + Mg hardness

The calcium and Mg hardness is the concentration of Ca & Mg ions expressed as equivalents of CaCO

3

For Mg=

M

Mg

M

CaCO

3

=

24.3

100.1

=4.1

So total hardness= 4.1[Mg

2+

]ppm of CaCO

3

Given 100kg of water contains 5g MgSO

4

i.e, 100L water contains 500mg of MgSO

4

=

M

MgSO

4

(500mg)24.3

=

120.7

(500mg)(24.3)

=100mg of Mg ims

∴[Mg

2+

]=100mg/100L=1mg/L

So hardness of water= 4.1[1mg/L]

=4.1ppm of CaCO

3