Question

Hardness of any water sample due to Ca(HCO₃)₂ is 120 mg in a litre. Calculate hardness in terms of CaCO₃ in ppm? (Equivalent weight of Ca(HCO₃)₂ is 50 g/equiv.)

a. 240 ppm
b. 120 ppm
c. 60 ppm
d. 480 ppm

Answer 1

The hardness of the water sample is 120 ppm in terms of CaCO3 when originally given as 120 mg/L of Ca(HCO3)2, considering the equivalent weight of both Ca(HCO3)2 and CaCO3 to be 50 g/equiv.

Step-by-step explanation:

The question asks to calculate the hardness of a water sample in terms of CaCO3 in ppm when the hardness due to Ca(HCO3)2 is given as 120 mg/L. To convert this value, we can use the equivalent weight of Ca(HCO3)2 which is 50 g/equiv.

First, let's determine the number of equivalents of Ca(HCO3)2 in 120 mg:

0.120 g / 50 g/equiv = 0.0024 equiv of Ca(HCO3)2

0.0024 equiv × 50 g/equiv = 0.12 g of CaCO3

0.12 g × 1000 mg/g = 120 mg/L of CaCO3

Therefore, the hardness in terms of CaCO3 is 120 ppm.