Final answer:
When solid Na₃PO₄ is added to the solution containing 0.0450 M Ca²⁺ and 0.0930 M Ag⁺, Ca₃(PO₄)₂ will precipitate out of the solution first. The remaining percentage of Ca²⁺ in solution when the second cation starts to precipitate is 67%.
Step-by-step explanation:
A solution contains 0.0450 M Ca²⁺ and 0.0930 M Ag⁺. When solid Na₃PO₄ is added, the phosphate species that will precipitate out of the solution first is Ca₃(PO₄)₂. This is because Ca²⁺ has a higher concentration than Ag⁺, so Ca₃(PO₄)₂ will form first due to the common ion effect.
When the second cation just starts to precipitate, the percentage of the first cation remaining in solution can be calculated using the mole ratios from the balanced equation. In this case, since Ca₃(PO₄)₂ precipitates first, the remaining percentage of Ca²⁺ in solution is 67%.