Give the meaning of transition element.
Identify two characteristic properties of transition elements.
The $\text{TiO}^{2+}$ ion is produced when $\text{TiO}_2$ reacts with excess sulfuric acid. In acidic conditions, zinc metal can reduce $\text{TiO}^{2+}$ to give a purple solution containing $\text{Ti}^{3+}(aq)$. $\text{TiO}^{2+}(aq)$ is a colourless ion. Suggest why.
State the electronic configuration of an isolated $\text{Ti}^{3+}$ ion.
Write an ionic equation for the reduction of $\text{TiO}^{2+}$ by zinc metal in acidic conditions.
Acidified $\text{Ti}^{3+}(aq)$ reacts with oxygen dissolved in water as shown. $4\text{Ti}^{3+} + \text{O}_2 + 2\text{H}_2\text{O} \rightarrow 4\text{TiO}^{2+} + 4\text{H}^+$, $\Delta G^{\circ} = -436.1\,\text{kJ mol}^{-1}$ The standard reduction potential, $E^{\circ}$, of $\text{O}_2 + 4\text{H}^+ + 4e^- \rightleftharpoons 2\text{H}_2\text{O}$ is $+1.23\,\text{V}$. Calculate the standard reduction potential, $E^{\circ}$, in V, of the $\text{TiO}^{2+}(aq)/\text{Ti}^{3+}(aq)$ half-cell. Show your working.
When aqueous citrate ions, $\text{C}_6\text{H}_5\text{O}_7^{3-}$, are added to $\text{Ti}^{3+}(aq)$, the $[\text{Ti}(\text{C}_6\text{H}_5\text{O}_7)_2]^{3-}(aq)$ complex forms. Explain, in terms of d-orbitals, why $\text{Ti}^{3+}$ can form complex ions.
Acidified $[\text{Ti}(\text{C}_6\text{H}_5\text{O}_7)_2]^{3-}(aq)$ does not react with oxygen dissolved in water, unlike acidified $\text{Ti}^{3+}(aq)$. Suggest what this tells you about the value of the standard reduction potential, $E^{\circ}$, of the following half-cell. $[\text{Ti}(\text{C}_6\text{H}_5\text{O}_7)_2]^{2-}(aq) + e^- \rightleftharpoons [\text{Ti}(\text{C}_6\text{H}_5\text{O}_7)_2]^{3-}(aq)$ Explain your answer.
Some reactions of $\text{TiO}_2$ are shown in Fig. 3.1. The titanium ions in $\text{TiF}_6^{2-}$ and $\text{Ti(acac)}_2\text{Cl}_2$ have a coordination number of 6. State what is meant by coordination number.
Write an equation for the formation of $\text{TiF}_6^{2-}$ from $\text{TiO}_2$.
State the meaning of bidentate ligand.
$\text{Ti(acac)}_2\text{Cl}_2$ displays both optical and geometrical (cis/trans) isomerism. $\text{Ti(acac)}_2\text{Cl}_2$ has three stereoisomers. The structure of one stereoisomer of $\text{Ti(acac)}_2\text{Cl}_2$ is shown in Fig. 3.2. Complete the structures of the other two stereoisomers of $\text{Ti(acac)}_2\text{Cl}_2$.
The $\text{acac}^-$ anion is symmetrical. Deduce which, if any, of stereoisomers 1, 2 and 3 in (d)(iv) are polar. Explain your answer.