**Passage 9:** What is the **total hardness** of the above water sample in ppm? — Mole Concept and Some Basic Concepts of Chemistry Chemistry Question

💡 Solution & Explanation

$\text{moles } CaCl_2 = 0.0111 / 111 = 10^{-4} \text{ mol}$. <br>$\text{Total moles } CaCO_3 \text{ eq} = 10^{-4} + 10^{-4} = 2 \times 10^{-4} \text{ mol}$. <br>$\text{Total mass } CaCO_3 \text{ eq} = 2 \times 10^{-4} \times 100 = 0.02 \text{ g} = 20 \text{ mg}$. <br>$\text{ppm} = (\text{mg solute} / \text{Volume in L}) = 20 / 0.1 = 200 \text{ ppm}$.