The mechanism for a ligand substitution reaction between [Co H2O 6]2+ and Cl- in aqueous solution can be described as follows:1. Initial complex: The starting complex is hexaaquacobalt II ion, [Co H2O 6]2+, which is an octahedral complex with six water molecules coordinated to the central cobalt II ion.2. Formation of an intermediate: A chloride ion Cl- from the aqueous solution approaches the [Co H2O 6]2+ complex and forms a bond with the cobalt II ion. This results in a seven-coordinate intermediate, where the cobalt II ion is bonded to six water molecules and one chloride ion.3. Dissociation of a water molecule: One of the water molecules in the seven-coordinate intermediate dissociates, leaving the complex. This results in the formation of a new octahedral complex, [Co H2O 5Cl]+, with five water molecules and one chloride ion coordinated to the cobalt II ion. The overall reaction can be represented as:[Co H2O 6]2+ + Cl- [Co H2O 5Cl]+ + H2OThis mechanism is known as an associative ligand substitution reaction, where the incoming ligand Cl- forms a bond with the metal ion before the dissociation of the original ligand H2O . The rate-determining step in this reaction is the formation of the seven-coordinate intermediate.