Direction: A water sample contains the following dissolved ions.
[Na+] = 56 mg/l; [Ca2+]
[Ca2+] = 40 mg/l; [Mg2+]
[Mg2+] = 30 mg/l; [Al3+]
[Al3+] = 3 mg/l; [HCO3]
[HCO3] = 190 mg/l; [Cl-]
[Cl-] = 165 mg/l; Water pH is 7.
Atomic weights: Ca: 40, Mg: 24, Al: 27, H: 1, C: 12, O: 16, Na: 23, Cl: 35.5.
-
The total hardness of the sample in mg/l as CaCO3 is
-
- 484
- 450
- 242
- 225
Correct Option: D
| Total solids as CaCO3 (mg/l) = Concentration of Mg2+ × | + Concentration of Ca2+ × | ||
| Eq. wt of Mg2+ | Eq. wt of Mg2+ |
| = 30 × | + 40 × | = 225 mg/l of CaCO3 | ||
| 12 | 20 |
