A sample of water has hardness expressed as 185 ppm Ca²⁺(aq).The sample is passed through an ion exchange column and the Ca²⁺(aq)ions are replaced by Na⁺(aq)ions.What is the [Na⁺] in ppm of the water after it has been treated? (1 ppm = 1 g solute/10⁶ g solution)

Question

Quizplus · Accepted Answer

The molar mass of Ca is 40 g/mol and Na is 23 g/mol. Since each Ca²⁺ ion is replaced by two Na⁺ ions, the concentration of Na⁺ will be (185 ppm * 2 * 23/40) = 212 ppm.

A Sample of Water Has Hardness Expressed as 185 Ppm