The flocculation value of HCl for As S sol is 30 mmolL . If H SO is used for the flocculation of ars — Surface Chemistry Chemistry Question

💡 Solution & Explanation

**Step 1: Understand flocculation value concept** Flocculation value is the minimum concentration of electrolyte needed to cause precipitation of a colloid. It's inversely proportional to the charge on the ion causing flocculation. **Step 2: Identify the relevant ions** - HCl flocculation value = 30 mmol/L (H⁺ is monovalent, charge = +1) - H₂SO₄ flocculation value = ? (H⁺ is monovalent, but SO₄²⁻ is divalent, charge = +2) **Step 3: Apply the flocculation relationship** For colloids with the same sign, the relationship is: $$\frac{C_1}{C_2} = \left(\frac{Z_2}{Z_1}\right)^3$$ Where C is concentration and Z is the charge of the coagulating ion. For H⁺ ions: Z₁ = 1 (from HCl) and Z₂ = 1 (from H₂SO₄) However, SO₄²⁻ is the actual coagulating anion with Z = 2: $$C_{\text{HCl}} \times 1^3 = C_{\text{H}_2\text{SO}_4} \times 2^3$$ $$30 = C_{\text{H}_2\text{SO}_4} \times 8$$ $$C_{\text{H}_2\text{SO}_4} = \frac{30}{8} = 3.75 \text{ mmol/L}$$ **Step 4: Calculate mass in 250 mL** Molar mass of H₂SO₄ = 98 g/mol Moles needed = 3.75 mmol/L × 0.250 L = 0.9375 mmol = 0.0009375 mol Mass = 0.0009375 mol × 98 g/mol = 0.091875 g ≈ **0.09 g** *Note: If using alternative