Question

200 mL of water sample has hardness equivalent to 25 mL of 0.08 N MgSO4. What is the hardness of the sample?

Answer 1

200 ml of water and density of water is 1 gm/ml .

Mass of water is 200 gram .

number of gram equivalent of MgSO₄ = number of gram equivalent of CaCO₃ .

So , number of gram equivalent of CaCO₃ = 0.002 gm equivalent...

moles of CaCO₃ =( 0.002 / 2 ) moles .

mass of CaCO₃ = 0.1 gm...

where mass = moles * molar mass ( molar mass of CaCO₃ = 100 gm/mol ).

Degree of Hardness = (Mass of CaCO₃ ) * 10⁶ / Mass of water .

Degree of Hardness = 0.1 *10⁶ / 200 = 500 ppm . answer.