Final answer:
The concentration of the H₃PO‚„ solution is 0.261 M.
Step-by-step explanation:
This question involves a titration between a phosphoric acid (H₃PO‚„) solution and a calcium hydroxide (Ca(OH)₂) solution. The titration requires 40.2 ml of the Ca(OH)₂ solution to reach the third equivalence point. To find the concentration of the H₃PO‚„ solution, we can use the equation:
H₃PO‚„ (aq) + 3Ca(OH)₂ (aq) →→→→ Ca₃(PO₄)₂ (aq) + 6H₂O (1)
Since the balanced equation shows a 1:3 molar ratio between H₃PO‚„ and Ca(OH)₂, we can calculate the concentration of the H₃PO‚„ solution by multiplying the concentration of the Ca(OH)₂ solution (1.05 M) by the volume ratio:
Concentration of H₃PO‚„ solution = (1.05 M) × (30.0 ml / 40.2 ml) × (1 / 3) = 0.261 M