Problem 100 When concentrated \(\mathrm{HCl}... [FREE SOLUTION] (2024)

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Coordination compounds are a unique class of substances in which metal atoms or ions are surrounded by various molecules or ions, called ligands. These ligands can donate electrons to the metal center, creating a wide array of complex structures with distinctive properties. For instance, the compound \( \left[\mathrm{Co}\left(\mathrm{H}_2 \mathrm{O}\right)_{6}\right]^{2+} \) is a coordination complex where cobalt (Co) is at the center, coordinated by six water molecules.

In the exercise, when concentrated hydrochloric acid (HCl) is added, the chlorine (Cl-) ions from the acid act as ligands and can replace the water molecules. This change in the ligands around the cobalt ion can lead to the different colors seen in coordination compounds. The color change is a visual representation of the ligand exchange process and reflects the unique properties of coordination compounds. These properties are essential in various applications, including colorimetry in analytical chemistry.

Le Chatelier's Principle is a critical concept in chemistry that predicts the behavior of a system at equilibrium when it experiences a change in concentration, pressure, volume, or temperature. The principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium will move to counteract the change.

In terms of our exercise example, when the Cl- ions are added to the system, Le Chatelier's Principle implies that the equilibrium will shift to decrease the concentration of the Cl- ions by forming a new complex. This principle helps understand the reactivity of the cobalt complex in the presence of additional chloride ions, ultimately leading to the formation of a new complex with an intense blue color.

Chemical equilibrium refers to the state in which the rates of the forward and reverse reactions are equal, leading to no net change in the concentrations of the reactants and products. It is a balance that is reached in a closed system and can be influenced by altering the conditions such as concentration, temperature, and pressure.

When concentrated HCl is added to the \( \left[\mathrm{Co}\left(\mathrm{H}_2 \mathrm{O}\right)_{6}\right]^{2+} \) solution, we see a shift in the equilibrium due to the increased concentration of Cl- ions. This disruption of equilibrium is essential for understanding the resultant color change and formation of a new coordination complex. This illustrates how equilibrium concepts are applied in coordination chemistry to predict the outcomes of reactions and the stability of new compounds formed.

Transition metal complexes form when transition metals act as the central metal ions surrounded by ligands. The transition metals, like cobalt in this exercise, have unique electronic configurations allowing them to form a variety of stable coordination complexes with different ligands.

These complexes often have distinctive colors depending on the metal ion and the ligands attached to them, due to the d-d electron transitions that are allowed in the presence of a ligand field. The intense blue color development mentioned in our exercise is indicative of such electronic transitions within the cobalt complex. Transition metal complexes are central to many biological systems, materials science, and catalysis, making their study fundamental in the field of coordination chemistry.