Question

You isolate a compound with the formula \(\mathrm{PtCl}_{4} \cdot 2 \mathrm{KCl}\). From electrical conductance tests of an aqueous solution of the compound, you find that three ions per formula unit are present, and you also notice that addition of \(\mathrm{AgNO}_{3}\) does not cause a precipitate. Give the formula for this compound that shows the complex ion present. Explain your findings. Name this compound.

Short answer

The compound's formula showing the complex ion present is K₂[PtCl₄K₂], and its name is Potassium hexachloroplatinate(IV). This formula shows that all the chloride ions are included in the complex ion, satisfying the given criteria of three ions per formula unit and no precipitate with AgNO₃.

Step-by-step solution

List Possible Dissociation Reactions

We are given the compound's formula as PtCl₄·2KCl. In water, the possible dissociation reactions for this compound can be: 1. PtCl₄²⁻ + 2K⁺ 2. [PtCl₄K₂]³⁻ + 2K⁺ 3. [PtCl₂K₂]²⁻ + 2K⁺

Verify the Number of Ions per Formula Unit

Given that the compound dissociates into three ions per formula unit, we can compare the possible reactions from Step 1 and eliminate the reactions that do not meet this requirement. 1. PtCl₄²⁻ + 2K⁺ → 3 ions ➔ Correct 2. [PtCl₄K₂]³⁻ + 2K⁺ → 3 ions ➔ Correct 3. [PtCl₂K₂]²⁻ + 2K⁺ → 4 ions ➔ Incorrect Since the compound shouldn't cause a reaction with AgNO₃, this suggests silver chloride (AgCl) is not precipitated. To identify which dissociation reaction satisfies this condition, the complex ion must contain all the chloride ions.

Check the AgNO₃ Reaction

Comparing candidate reactions from Step 2, we need the one where all chloride ions are included in the complex ion and not free chloride ions are present. 1. PtCl₄²⁻ + 2K⁺ → Free chloride ions available, AgCl can precipitate ➔ Incorrect 2. [PtCl₄K₂]³⁻ + 2K⁺ → No free chloride ions available, AgCl won't precipitate ➔ Correct

Identify the Compound's Formula and Name

From the analysis above, we found that the dissociation reaction which agrees with the given criteria (three ions/formula unit and no precipitate with AgNO₃) is: [PtCl₄K₂]³⁻ + 2K⁺ Hence the compound's formula showing the complex ion present is K₂[PtCl₄K₂]. This compound can be named as Potassium hexachloroplatinate(IV).