Question

A sample of water has a hardness of 120 ppm CaCo3. What is the concenttration of Ca2+ in moles/liters? Show Wrok!

Answer 1

CaCO₃           Ca²⁺ + CO₃^2-

Molar mass of CaCO₃ = 100.08 g/mol

Here, concentration of CaCO₃       = 120 ppm                 [Note: 1 ppm = 1 mg/L]

                                                       = 120 mg/L

                                                       = 0.12 g/L

                                                       = (0.12/100.08) mol/L

                                                       = 1.2 x 10^-3 mol/L

Concenttration of Ca²⁺       = 1.2 x 10^-3 mol/L