Complete the sentence so that it describes the colour change observed in this reaction. The colour changes from ................. to ................. .
Write a formula for the stability constant, $K_{\text{stab}}$, of $[\text{Co(NH}_3)_6]^{2+}$.
The value of $K_{\text{stab}}$ for $[\text{Co(NH}_3)_6]^{2+}$ is $7.7 \times 10^4$. What conclusion can be drawn about the properties of $[\text{Co(NH}_3)_6]^{2+}$ and $[\text{Co(H}_2\text{O})_6]^{2+}$ from this $K_{\text{stab}}$ value?
Using the fact that $[\text{Co(NH}_3)_6]^{3+} + e^- \rightleftharpoons [\text{Co(NH}_3)_6]^{2+}$ has $E^{\circ} = +0.10\,\text{V}$, and the Data Booklet, calculate the $E^{\circ}_{\text{cell}}$ value for the oxidation of $[\text{Co(NH}_3)_6]^{2+}$.
Write an ionic equation for the oxidation of $[\text{Co(NH}_3)_6]^{2+}$.
Predict, by selecting suitable data from the Data Booklet, whether oxygen can oxidise $\text{Co}^{2+}(aq)$ in acidic solution when ammonia is absent. Explain your answer.