Chapter 22: Problem 52
A student has prepared a cobalt complex that has one of the following three structures: \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right] \mathrm{Cl}_{3}\), \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}\right] \mathrm{Cl}_{2},\) or \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}\right] \mathrm{Cl} .\) Explain how the student would distinguish between these possibilities by an electrical conductance experiment. At the student's disposal are three strong electrolytes \(-\mathrm{NaCl}, \mathrm{MgCl}_{2}\), and \(\mathrm{FeCl}_{3}-\) which may be used for comparison purposes.
Short Answer
Expert verified
Compare conductance: if it matches NaCl's, it's Structure 3; MgCl2's, it's Structure 2; FeCl3's, it's Structure 1.
Step by step solution
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Electrical Conductance
Electrical conductance is important in understanding how well a solution can carry an electric current. It relies on free-moving charged particles, mainly ions, in the solution. The higher the number of ions, the greater the conductance.
In this experiment, electrical conductance serves as a helpful tool to determine the structure of a cobalt complex. Each different structure will dissociate to release a different number of ions, affecting the conductance. More ions mean higher conductance, while fewer ions mean lower conductance. Thus, by measuring how well the solution conducts electricity, we can infer the number of ions and relate it to the structure of the cobalt complex.
In this experiment, electrical conductance serves as a helpful tool to determine the structure of a cobalt complex. Each different structure will dissociate to release a different number of ions, affecting the conductance. More ions mean higher conductance, while fewer ions mean lower conductance. Thus, by measuring how well the solution conducts electricity, we can infer the number of ions and relate it to the structure of the cobalt complex.
Electrolyte Dissociation
Electrolyte dissociation is the process by which a compound separates into its individual ions when dissolved in a solvent like water. Strong electrolytes disassociate completely, leading to a large number of free ions.
The dissociation process is crucial in determining the cobalt complex's structure through electrical conductance. Each of the possible cobalt complexes dissociates differently:
The dissociation process is crucial in determining the cobalt complex's structure through electrical conductance. Each of the possible cobalt complexes dissociates differently:
- The first complex, \([\mathrm{Co}(\mathrm{NH}_3)_6]\mathrm{Cl}_3\), breaks into four ions.
- The second, \([\mathrm{Co}(\mathrm{NH}_3)_5 \mathrm{Cl}]\mathrm{Cl}_2\), breaks into three ions.
- The third, \([\mathrm{Co}(\mathrm{NH}_3)_4 \mathrm{Cl}_2]\mathrm{Cl}\), breaks into two ions.
Coordination Compounds
Coordination compounds involve a central metal atom or ion surrounded by molecules or ions called ligands. These complexes are often characterized by their geometries and the number of ions that dissociate in solution.
In our exercise, cobalt serves as the central metal ion. The ammonia molecules (NH3) and chloride ions (Cl-) are the ligands that complete the coordination sphere. Understanding how these components fit together gives insight into their chemical behavior, especially regarding ionic dissociation and resulting electrical conductance. The different ligands impact stability and dissociation patterns, which in turn affect the number of ions in solution.
In our exercise, cobalt serves as the central metal ion. The ammonia molecules (NH3) and chloride ions (Cl-) are the ligands that complete the coordination sphere. Understanding how these components fit together gives insight into their chemical behavior, especially regarding ionic dissociation and resulting electrical conductance. The different ligands impact stability and dissociation patterns, which in turn affect the number of ions in solution.
Ion Comparison
The experiment consists of comparing the dissociated ions from the cobalt complexes to known strong electrolytes: NaCl, MgCl2, and FeCl3. Each of these standard compounds dissociates into a specific number of ions:
By comparing the electrical conductance of the unknown cobalt complex with these known standards, the student can determine how many ions are released, thus indicating which cobalt structure is present. Comparing conductance directly ties the number of ions released by a compound to its structural identity.
- NaCl dissociates into 2 ions;
- MgCl2 dissociates into 3 ions;
- FeCl3 dissociates into 4 ions.
By comparing the electrical conductance of the unknown cobalt complex with these known standards, the student can determine how many ions are released, thus indicating which cobalt structure is present. Comparing conductance directly ties the number of ions released by a compound to its structural identity.
Complex Ion Formations
Complex ion formations involve how a central ion, such as cobalt, bonds with ligands to form a stable structure. The arrangement and charge of ligands like NH3 and Cl- influence how the complex dissociates within a solution.
For the cobalt complexes at hand, knowing the formation aids in predicting dissociation patterns and electrical conductance. Each structure's specific formation and ionic charge distribution result in unique dissociation paths. These paths ultimately dictate the number of ions released and aid in deducing the correct structure through conductance experiments.
For the cobalt complexes at hand, knowing the formation aids in predicting dissociation patterns and electrical conductance. Each structure's specific formation and ionic charge distribution result in unique dissociation paths. These paths ultimately dictate the number of ions released and aid in deducing the correct structure through conductance experiments.
