Problem 12 - Chemistry An Atoms First Approach

Question

When \(\mathrm{Na}_{3} \mathrm{PO}_{4}(a q)\) is added to a solution containing a metal ion and a precipitate forms, the precipitate generally could be one of two possibilities. What are the two possibilities?

Step-by-Step Solution

Answer

When Na3PO4 is added to a solution containing a metal ion, the precipitate formed could generally be one of two possibilities: silver phosphate (Ag3PO4) or calcium phosphate (Ca3(PO4)2). These are the most common insoluble phosphate compounds that form precipitates with metal ions.

Step 1: List the Metal Ions Commonly Forming Precipitates with Phosphates

Some metal ions are known to form insoluble phosphate compounds which precipitate when Na3PO4 is added to a solution containing them. The most common possibilities are silver (Ag+), calcium (Ca²⁺), and magnesium (Mg²⁺). We will evaluate these possibilities.

Step 2: Write Out the Possible Chemical Reactions

The possible reactions between the phosphate ion (PO₄³⁻) and the metal ions are: 1. Ag⁺ + PO₄³⁻ → Ag₃PO₄ (s) 2. Ca²⁺ + PO₄³⁻ → Ca₃(PO₄)₂ (s) 3. Mg²⁺ + PO₄³⁻ → Mg₃(PO₄)₂ (s)

Step 3: Determine the Most Likely Precipitates

Based on the balanced chemical reactions in step 2 and the metal ions commonly known to form insoluble phosphate compounds, the two most likely possibilities of the precipitates formed when Na3PO4 is added to a solution containing a metal ion are: 1. Silver Phosphate (Ag3PO4) 2. Calcium Phosphate (Ca3(PO4)2) These are the two typical precipitates formed when sodium phosphate is added to a solution containing metal ions.