Explain why iron shows variable oxidation states.
Complete the shorthand electronic configurations of Fe and $\text{Fe}^{3+}$. Fe \quad $[\text{Ar}]\,\ldots$ $\text{Fe}^{3+}$ \quad $[\text{Ar}]\,\ldots$
Define the term complex.
State the coordination number of Fe in $[\text{Fe}(\text{H}_2\text{O})_6]^{3+}$.
The $\text{H}-\text{O}-\text{H}$ bond angle in water is $104.5^{\circ}$. Suggest the $\text{H}-\text{O}-\text{H}$ bond angle in $[\text{Fe}(\text{H}_2\text{O})_6]^{3+}$. Explain your answer.
Explain why iron complexes are coloured.
Aqueous solutions of complexes $[\text{Fe}(\text{H}_2\text{O})_6]^{3+}$ and $[\text{Fe}(\text{H}_2\text{O})_5\text{SCN}]^{2+}$ are different colours. Explain why these complexes are different colours.
Explain why iron complexes are coloured.
The aqueous solutions of $[\text{Fe}(\text{H}_2\text{O})_6]^{3+}$ and $[\text{Fe}(\text{H}_2\text{O})_5\text{SCN}]^{2+}$ do not have the same colour. Explain why.
$[\text{Fe}(\text{H}_2\text{O})_5(\text{H}_2\text{PO}_4)]^{2+}$ can be formed when $\text{H}_3\text{PO}_4$ reacts with $[\text{Fe}(\text{H}_2\text{O})_6]^{3+}$. Write an equation for this reaction.
Write an expression for $K_{\text{stab}}$ of $[\text{Fe}(\text{H}_2\text{O})_5\text{SCN}]^{2+}$ and state its units.
Use the stability constant data in Table 3.1 to calculate the value of the equilibrium constant, $K_c$, for the following equilibrium: $[\text{Fe}(\text{H}_2\text{O})_5(\text{H}_2\text{PO}_4)]^{2+} + \text{SCN}^- \rightleftharpoons [\text{Fe}(\text{H}_2\text{O})_5\text{SCN}]^{2+} + \text{H}_2\text{PO}_4^-$