Define what is meant by a complex ion.
Separate samples of $[\text{Co(H}_2\text{O)}_6]^{2+}$ are reacted with aqueous sodium hydroxide and with excess aqueous ammonia. State the following for each reaction. • Reaction of $[\text{Co(H}_2\text{O)}_6]^{2+}$ with aqueous sodium hydroxide: colour and state of the cobalt-containing species; ionic equation; reaction type. • Reaction of $[\text{Co(H}_2\text{O)}_6]^{2+}$ with excess aqueous ammonia: colour and state of the cobalt-containing species; ionic equation; reaction type.
On adding concentrated hydrochloric acid to a solution containing $[\text{Co(H}_2\text{O)}_6]^{2+}$, a blue solution of $[\text{CoCl}_4]^{2-}$ is produced and this equilibrium is set up. $[\text{Co(H}_2\text{O)}_6]^{2+} + 4\text{Cl}^- \rightleftharpoons [\text{CoCl}_4]^{2-} + 6\text{H}_2\text{O}$ Using Le Chatelier’s principle, predict the observations when silver nitrate solution is added dropwise to the blue solution of $[\text{CoCl}_4]^{2-}$. Explain your answer.
The $[\text{Co(NH}_3\text{Cl}_3]$ complex displays stereoisomerism. Complete the three-dimensional diagrams to show the two isomers of $[\text{Co(NH}_3\text{Cl}_3]$. Suggest the type of stereoisomerism.
$X$, $\text{C}_6\text{H}_{18}\text{N}_4$, is a tetradentate ligand. Suggest why a single molecule of $X$ can make four dative bonds.
$\text{C}_6\text{H}_{18}\text{N}_4$ reacts with aqueous cobalt(II) ions, $[\text{Co(H}_2\text{O)}_6]^{2+}$, in a $1:1$ ratio to make a new complex ion. Write an equation for this reaction.