Question

Upon addition of compound ( X ) to an aqueous AgNO(_3) solution, a white precipitate appears instantly. Also, ( X ) does not exhibit geometrical isomerism. The CORRECT option(s) for ( X ) is/are:

• A. ([Cr(OH_2)_4Cl_2]Cl)
• B. ([Cr(OH_2)_5Cl]Cl_2)
• C. ([Cr(OH_2)_6]Cl_3)
• D. ([Cr(OH_2)_3Cl_3])

Hint:

For identifying free ions in coordination compounds, focus on the ligands inside and outside the coordination sphere. Also, compounds with symmetrical ligands generally do not exhibit geometrical isomerism.

Answer 1

The Correct Option is B

Step 1: Understanding the reaction with AgNO\(_3\).

When a coordination compound reacts with AgNO\(_3\) to give a white precipitate of AgCl, it indicates the presence of free chloride ions (\(\text{Cl}^-\)) in the solution. The number of such free chloride ions depends on the charge of the coordination complex.

Step 2: Analyzing the options.

• Option (A): \([\text{Cr}(\text{OH}_2)_4\text{Cl}_2]\text{Cl}\)

This compound has 1 free \(\text{Cl}^-\) ion in solution. However, it exhibits geometrical isomerism due to the cis/trans arrangement of the two chlorides within the coordination sphere, so it is incorrect.

• Option (B): \([\text{Cr}(\text{OH}_2)_5\text{Cl}]\text{Cl}_2\)

This compound has 2 free \(\text{Cl}^-\) ions in solution. Since all ligands within the coordination sphere are monodentate and symmetrical, it does not exhibit geometrical isomerism, making this option correct.

• Option (C): \([\text{Cr}(\text{OH}_2)_6]\text{Cl}_3\)

This compound has 3 free \(\text{Cl}^-\) ions in solution. It has no geometrical isomers as all ligands are identical, making this option correct.

• Option (D): \([\text{Cr}(\text{OH}_2)_3\text{Cl}_3]\)

This compound does not have any free \(\text{Cl}^-\) ions in solution, as all chlorides are within the coordination sphere. Moreover, it exhibits geometrical isomerism, making this option incorrect.

Step 3: Conclusion.

The compounds \([\text{Cr}(\text{OH}_2)_5\text{Cl}]\text{Cl}_2\) and \([\text{Cr}(\text{OH}_2)_6]\text{Cl}_3\) satisfy the conditions given in the question, making options (B) and (C) correct.