Question

If a sample of water contains 50mg of MgCl2 per litre, calculate the hardness in
terms of CaCO3 equivalents.​

Answer 1

The hardness of water in terms of CaCO₃ equivalents is 52.63 mg/l

Explanation:

Given:

A sample of water contains 50 mg of MgCl₂ per litre

To calculate:

The hardness of water in terms of CaCO₃ equivalents

Solution:

We know that the hardness is due to multivalent ions of Mg and Ca primarily

The balanced equation is:

$MgCl_2+Na_2CO_3\rightarrow MgCO_3+2NaCl$

According to the above

1 mole of MgCl₂ gives 1 moles of CaCO₃

or, 95 gram of MgCl₂ gives 100 grams of CaCO₃

or, 1 gram of MgCl₂ gives 100/95 grams of CaCO₃

or, 50 mg of MgCl₂ gives (100/95) × 50 mg of CaCO₃ = 52.63 mg of CaCO₃

Therefore, the hardness of water = 52.63 mg/l as CaCO₃

Hope this answer is helpful.

Know More:

Q: A water sample contains 200 mg of caSO4 per litre calculate the hardness in terms of caco3 equivalent in milligram per litre PPM .

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