Chemistry of transition elements — Chemistry 9701 AS & A Level Question & Worked Solution

(a)[2]

On the diagram below, produce a neat labelled sketch that shows the shape and symmetry of a typical $d$-orbital.

(b(i))

Draw an orbital energy diagram to represent this, showing how many orbitals are in each set.

(b(ii))[7]

Use your diagram to help explain why: • Transition element complexes often have colour. • The colour of a complex of the same transition element frequently changes when the surrounding ligands are altered.

(c(i))

Calculate the oxidation number of carbon in the ethanedioate ion.

(c(ii))

Calculate the oxidation number of iron in $[\text{Fe(C}_2\text{O}_4)_3]^{3-}$.

(c(iii))

In the $[\text{Fe(C}_2\text{O}_4)_3]^{3-}$ ion, the iron atom is octahedrally enclosed by six oxygen atoms. Finish the displayed formula of this ion below.

(c(iv))[5]

In sunlight, the complex breaks down to potassium ethanedioate, iron(II) ethanedioate and carbon dioxide. Use oxidation numbers to support the balancing of the following decomposition equation. $\text{K}_3\text{Fe(C}_2\text{O}_4)_3 \rightarrow \ldots\text{K}_2\text{C}_2\text{O}_4 + \ldots\text{FeC}_2\text{O}_4 + \ldots\text{CO}_2$

Chemistry of transition elements — practice question

Worked solution & mark scheme