Define what is meant by complex ion.
Separate samples of $[\text{Co(H}_2\text{O)}_6]^{2+}$ are each treated with aqueous sodium hydroxide and with excess aqueous ammonia. Give the following details about these reactions. • for the reaction of $[\text{Co(H}_2\text{O)}_6]^{2+}$ with aqueous sodium hydroxide: colour and state of the cobalt-containing species; ionic equation; type of reaction. • for the reaction of $[\text{Co(H}_2\text{O)}_6]^{2+}$ with excess aqueous ammonia: colour and state of the cobalt-containing species; ionic equation; type of reaction.
If concentrated hydrochloric acid is added to a solution containing $[\text{Co(H}_2\text{O)}_6]^{2+}$, a blue solution of $[\text{CoCl}_4]^{2-}$ is formed and the following equilibrium is set up. $[\text{Co(H}_2\text{O)}_6]^{2+} + 4\text{Cl}^- \rightleftharpoons [\text{CoCl}_4]^{2-} + 6\text{H}_2\text{O}$ Use Le Chatelier’s principle to suggest the expected observations when silver nitrate solution is added dropwise to the blue solution of $[\text{CoCl}_4]^{2-}$. Explain your answer.
The $[\text{Co(NH}_3)_3\text{Cl}_3]$ complex shows stereoisomerism. Complete the 3D diagrams to display the two isomers of $[\text{Co(NH}_3)_3\text{Cl}_3]$. Suggest the type of stereoisomerism.
Compound $X$, $\text{C}_6\text{H}_{18}\text{N}_4$, is a tetradentate ligand. Suggest why a single molecule of $X$ can form four dative bonds.
React $\text{C}_6\text{H}_{18}\text{N}_4$ with aqueous cobalt(II) ions, $[\text{Co(H}_2\text{O)}_6]^{2+}$, in a $1:1$ ratio to produce a new complex ion. Write an equation for this reaction.