Describe and explain how cobalt’s density and melting point compare with those of calcium.
Transition metals can form complexes. What is meant by the term transition metal complex?
Cobalt can form the compounds $[\text{Co(NH}_3\text{)}_5\text{Br}]\text{SO}_4$ and $[\text{Co(NH}_3\text{)}_5\text{SO}_4]\text{Br}$. These two compounds are structural isomers. Define the term structural isomer.
Draw a three-dimensional diagram to show the structure of the ion $[\text{Co(NH}_3\text{)}_5\text{Br}]^{2+}$. Name its shape.
State the type of bonding between the cobalt ion and NH$_3$ groups in the $[\text{Co(NH}_3\text{)}_5\text{Br}]^{2+}$ ion.
State the oxidation number of cobalt in: • $[\text{Co(NH}_3\text{)}_5\text{Br}]^{2+}$ • $[\text{Co(NH}_3\text{)}_5\text{SO}_4]^+$
The compounds $[\text{Co(NH}_3\text{)}_5\text{Br}]\text{SO}_4$ and $[\text{Co(NH}_3\text{)}_5\text{SO}_4]\text{Br}$ can be told apart by simple chemical tests. Assume that anything bonded to the cobalt ion does not take part in these tests. Fill in the table with two different tests that could be used to identify each compound positively. State the expected observation with each compound.
The two compounds $[\text{Co(NH}_3\text{)}_5\text{Br}]\text{SO}_4$ and $[\text{Co(NH}_3\text{)}_5\text{SO}_4]\text{Br}$ are different colours. Explain why the colours of the two compounds are different.
Some transition metals and their compounds work as catalysts. Catalysis may be classed as heterogeneous or homogeneous. Complete the table by putting one tick in each row to show the type of catalysis in each reaction: • Fe in the Haber process • Fe$^{2+}$ in the $\text{I}^-$/S$_2$O$_8^{2-}$ reaction • NO$_2$ in the oxidation of SO$_2$ • V$_2$O$_5$ in the Contact process