What volume of 0.200 M KOH must be added to 17.5 mL of 0.135 M H₃PO₄to reach the third equivalence point? A)3.94 mL B)11.8 mL C)17.5 mL D)23.6 mL E)35.4 mL

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To reach the third equivalence point, all three protons of H3PO4 must be neutralized. The moles of H3PO4 are 0.135 M * 0.0175 L = 0.0023625 mol. Since each H3PO4 has 3 protons, 0.0023625 mol * 3 = 0.0070875 mol of KOH are needed. The volume of 0.200 M KOH required is 0.0070875 mol / 0.200 M = 0.0354375 L, or 35.4 mL.

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