**Passage 7 (continued):** <br> **Q2:** The hardness due to in ppm is: — Redox Reactions and Volumetric Analysis Chemistry Question

💡 Solution & Explanation

**Step 1:** $EDTA$ for $Mg^{2+} = \text{Total } - Ca^{2+} = 10 - 6 = 4$ mL. <br>**Step 2:** Moles $Mg^{2+} = 4 \times 0.01 / 1000 = 4 \times 10^{-5}$ in $100$ mL. <br>**Step 3:** Moles in $1$ L = $4 \times 10^{-4}$. <br>**Step 4:** Mass $CaCO_3 \text{ equiv} = 4 \times 10^{-4} \times 100 = 0.04$ g = $40$ mg/L = $40$ ppm.