Give the electronic configuration of an isolated, gaseous $\text{Cr}^{3+}$ ion. $1s^2$ .........................
Define what is meant by complex ion.
The aqueous complex $[\text{Cr}(\text{H}_2\text{O})_6]^{3+}(aq)$ has some chemical similarities to $[\text{Co}(\text{H}_2\text{O})_6]^{2+}(aq)$. Separate samples of $[\text{Cr}(\text{H}_2\text{O})_6]^{3+}$ are treated with $\text{NaOH}(aq)$, $\text{H}_2\text{O}_2(aq)$, and excess $\text{NH}_3(aq)$. Using this information and the Data Booklet, suggest the formula of the chromium species formed. State the type of reaction in each instance.
$[\text{Cr}(\text{H}_2\text{O})_6]^{2+}$ and $[\text{Cr}_2(\text{O}_2\text{CCH}_3)_4(\text{H}_2\text{O})_2]$ are both chromium(II) complexes, yet they show different colours. Explain why these complexes are not the same colour.
Water and ethanoate ions act as different kinds of ligand in this complex. Suggest an explanation for this statement.
Deduce the coordination number of Cr and the shape around each Cr atom in this structure.
State what type of bond links the two atoms in the Cr-Cr bond.
Construct an ionic equation for how $\text{Cr}^{2+}(aq)$ reacts with $\text{O}_2(aq)$ in acidic conditions.
Calculate $E^\circ_{\text{cell}}$ for the reaction given in (e)(i).