Problem 137 - A Complete Resource Book in Chemistry for JEE Main

Question

For the coordination compound \(\mathrm{PtCl}_{4} \cdot 5 \mathrm{NH}_{3}\), the charge on cation is found to be \(+3\). How many ions are furnished on ionization of the complex?

Step-by-Step Solution

Answer

The complex furnishes four ions upon ionization.

Step 1: Understand the Complex Composition

The given coordination compound is written as \(\mathrm{PtCl}_{4} \cdot 5 \mathrm{NH}_{3}\). This indicates a complex compound potentially best represented as \([\mathrm{Pt(NH}_3)_5\mathrm{Cl}] \mathrm{Cl}_3\). This arrangement suggests that one \([\mathrm{Pt(NH}_3)_5\mathrm{Cl}]^{3+}\) complex cation and three chloride ions \(\mathrm{Cl}^-\) are present outside the coordination sphere.

Step 2: Identify the Cation and Anion

From the formula \([\mathrm{Pt(NH}_3)_5\mathrm{Cl}] \mathrm{Cl}_3\), we identify that the cation is \([\mathrm{Pt(NH}_3)_5\mathrm{Cl}]^{3+}\) and the anions are three \(\mathrm{Cl}^-\) ions. Thus, the \([\mathrm{Pt(NH}_3)_5\mathrm{Cl}]\) forms a cation with a charge of \(+3\), which is balanced by three \(\mathrm{Cl}^-\) ions.

Step 3: Determine Ionization

Upon ionization, the cation \([\mathrm{Pt(NH}_3)_5\mathrm{Cl}]^{3+}\) and the three \(\mathrm{Cl}^-\) anions separate. This means the compound ionizes to form a total of four ions: one \([\mathrm{Pt(NH}_3)_5\mathrm{Cl}]^{3+}\) cation and three \(\mathrm{Cl}^-\) anions.

Key Concepts

Ionization

Ionization in coordination compounds refers to the process where a complex compound dissolves in a solution, separating into ions.
This concept is crucial as it helps to understand the behavior and properties of compounds in aqueous solutions.
For the compound \(\mathrm{PtCl}_{4} \cdot 5 \mathrm{NH}_{3}\), representing it as \([\mathrm{Pt(NH}_3)_5\mathrm{Cl}] \mathrm{Cl}_3\), means that on ionization:

• The cation \([\mathrm{Pt(NH}_3)_5\mathrm{Cl}]^{3+}\) is one of the ions produced.
• The anions, which are three \(\mathrm{Cl}^-\), separate from the cation, leading to four distinct ions.

Understanding ionization allows us to predict the number of ions a compound will produce in solution, impacting the compound's conductivity and how it reacts with other substances.
Knowing how many ions form is important for calculating properties like osmotic pressure and electrical conductivity in solution.

Complex Ions

Complex ions are formed when a central metal atom or ion is surrounded by molecules or anions, known as ligands, forming a coordination complex.
In the case of \([\mathrm{Pt(NH}_3)_5\mathrm{Cl}]^{3+}\), platinum (Pt) acts as the central metal atom.
Its surroundings consist of 5 ammonia \((\mathrm{NH}_3)\) molecules and one chloride ion \((\mathrm{Cl}^-)\), creating a charged complex - the \([\mathrm{Pt(NH}_3)_5\mathrm{Cl}]^{3+}\) ion.

• This particular ion has a +3 charge, indicating an overall loss of three electrons compared to the neutral state.
• The ligands \((\mathrm{NH}_3)\) are neutral, while chloride contributes to the net charge.

Complex ions are essential in coordination chemistry due to their unique structures, varied shapes, and compositions.
They play significant roles, not just in chemistry but also in biological systems and industrial processes.

Coordination Chemistry

Coordination chemistry focuses on the study of compounds composed of a central atom or ion, usually metallic, bonded to surrounding ligands.
These compounds are called coordination compounds and can vary in complexity and function.
With \([\mathrm{Pt(NH}_3)_5\mathrm{Cl}] \mathrm{Cl}_3\), we see a beautiful example of how intricate coordination chemistry can get.

• The central concept involves the coordination sphere, where the metal ion and its attached ligands reside.
• Outside this coordination sphere are ions or molecules (counter-ions) that balance the compound's net charge.

The intricacies of this chemistry explain how compounds like \(\mathrm{PtCl}_{4} \cdot 5 \mathrm{NH}_{3}\) dissociate into ions and maintain charge balance.
Applications of coordination chemistry are vast, including fields like catalysis, materials science, and medicine, illustrating its profound impact on many scientific areas.