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

Question

For the coordination compound \(\mathrm{PtCl}_{4} .5 \mathrm{NH}_{3}\), 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 5 ions upon ionization.

Step 1: Analyze the Coordination Compound

The given coordination compound is \(\mathrm{PtCl}_{4} .5 \mathrm{NH}_{3}\). This indicates that a platinum ion (Pt) is at the center, surrounded by 5 ammonia molecules (\(\mathrm{NH}_3\)) and 4 chloride ions (\(\mathrm{Cl^-}\)). Ammonia acts as a neutral ligand and does not affect the charge.

Step 2: Determine the Charge of Platinum

We know from the problem that the charge on the cation of the complex is \(+3\). Therefore, the platinum ion (Pt) must have a charge of \(+3\), as ammonia is neutral and does not contribute to the complex's charge.

Step 3: Calculate Charge Contribution from Chlorides

Each chloride ion (\(\mathrm{Cl^-}\)) carries a charge of \(-1\). With 4 chloride ions present, their total contribution to the charge is \(-4\). Since the overall charge of the complex is the sum of the charges, the charge calculation becomes important.

Step 4: Set Up the Equation for Charge Balance

Set up the charge balancing equation: \[ \mathrm{Charge\,on\,Pt} + 4 \times (-1) = +3 \] \[ +3 + 4(-1) = 0 \] This implies that in the ionic form outside of the complex, Cl ions balance to zero charge resulting in a discrete Pt entity with \(+3\) remaining.

Step 5: Determine Number of Ions from Ionization

Upon ionization, the compound separates into a \(\mathrm{Pt(NH}_3)_5^{3+}\) cation and 4 \(\mathrm{Cl}^-\) anions. Therefore, the number of ions furnished upon ionization is \(1 + 4 = 5\).

Key Concepts

Charge Balancing

In coordination compounds, charge balancing is crucial to maintaining stability. The overall charge of a compound is determined by the charges of its constituent elements and ions.
In the case of \(\mathrm{PtCl}_{4} .5 \mathrm{NH}_{3}\), the charge on the cation, provided by the problem, is \(+3\). Chloride ions each carry a charge of \(-1\), which contributes to a total of \(-4\) for the four chloride ions.
When determining the charge of the metal center, in this case, platinum (Pt), it must balance the negative charges from the chlorides while considering the neutral nature of the ammonia ligands. Thus, the charge balance equation makes sure all components add up to the total charge of the coordination complex.

Ligands

Ligands play a vital role in the formation of coordination compounds. They are atoms, ions, or molecules that donate electron pairs to a central metal atom or ion, forming coordination bonds.
In \(\mathrm{PtCl}_{4} .5 \mathrm{NH}_{3}\), ammonia (\(\mathrm{NH}_3\)) acts as a ligand. It's a neutral molecule, meaning it doesn't add to or subtract from the total charge of the compound. Each ammonia donates an electron pair to the platinum, influencing the geometry and stability of the coordination compound.
The presence of ligands like ammonia is central to the compound's chemistry by defining its structure, reactivity, and overall charge distribution.

Ionization

Ionization refers to the process where a compound dissociates to form ions. In coordination complexes, this process involves separation into cations and anions.
For \(...\), when it ionizes in solution, it breaks down into a **\(\mathrm{Pt(NH}_3)_5^{3+}\)** cation and four **\(\mathrm{Cl}^-\)** anions.

• This separation is essential in determining the number of ions produced.
• Understanding ionization helps in understanding how various properties such as solubility and electrical conductivity, are influenced.

The coordination complex, upon ionization, results in a total of five ions.

Chloride Ions

Chloride ions are an essential part of many coordination compounds. They not only determine the compound's charge but also influence its reactivity and solubility.
In the coordination compound **\(\mathrm{PtCl}_{4} .5 \mathrm{NH}_{3}\)**, four chloride ions each carry a charge of **\(-1\)**. This contributes significantly to the overall charge balance equation: \(+3 + 4(-1) = 0\).

• The loss of these chloride ions during ionization affects the charge distribution and number of ions released.
• They also play a critical role in buffering the positive charge of the central platinum in solution.

Understanding the role of chloride ions is crucial for grasping the broader concepts of chemistry involved in coordination complexes.