See image — AITS & Test Series Chemistry Question

💡 Solution & Explanation

4 H 10       4 2 10 Ca M 2         Weight of 2 4 Ca 20 10 g in 1 L     4 6 2 6 2 3 20 10 10 Weight of Ca ion in 10 mL H O 10       = 2  Hardness = 2 ppm.