Group 2 nitrates break down when heated. Describe how their thermal stability varies as proton number increases. Explain your answer.
Copper(II) nitrate breaks down in a similar way to Group 2 nitrates. Write an equation for the decomposition of $\text{Cu(NO}_3)_2$.
$\text{Cu(NO}_3)_2(s)$ is placed in water to make solution $A$. Fig. 1.1 illustrates several reactions of solution $A$. Complete Table 1.1 by giving the formula of each copper-containing species present in $A$, $B$, $C$ and $D$, together with the colour of every copper-containing species formed.
$\text{EDTA}^{4-}$ is a polydentate ligand. Explain what is meant by a polydentate ligand.
Group 2 metal ions can form complexes similar to those of transition elements. An aqueous solution of $\text{EDTA}^{4-}$ is added to water containing $[\text{Ca(H}_2\text{O)}_6]^{2+}$ to produce a new complex, $[\text{CaEDTA}]^{2-}$, as shown. equilibrium 1: $[\text{Ca(H}_2\text{O)}_6]^{2+} + \text{EDTA}^{4-} \rightleftharpoons [\text{CaEDTA}]^{2-} + 6\text{H}_2\text{O}$ On the structure of $\text{EDTA}^{4-}$ in Fig. 1.2, circle the six atoms that bond with the metal ion.
The calcium ions in $[\text{Ca(H}_2\text{O)}_6]^{2+}$ and $[\text{CaEDTA}]^{2-}$ each have a coordination number of 6. Explain what is meant by coordination number.
The complex $[\text{CaEDTA}]^{2-}$ may be used to remove poisonous metals from the body. An aqueous solution of $[\text{CaEDTA}]^{2-}$ is added to a solution containing equal concentrations of $\text{Cr}^{3+}(aq)$, $\text{Fe}^{3+}(aq)$ and $\text{Pb}^{2+}(aq)$. The mixture is then allowed to reach equilibrium. State the type of reaction when $[\text{CaEDTA}]^{2-}$ reacts with $\text{Cr}^{3+}(aq)$, $\text{Fe}^{3+}(aq)$ and $\text{Pb}^{2+}(aq)$.
Deduce the relative concentrations of $[\text{CrEDTA}]^{-}$, $[\text{FeEDTA}]^{-}$ and $[\text{PbEDTA}]^{2-}$ present in the resulting mixture. Explain your answer. Use the form: $\text{highest concentration} > \dots > \text{lowest concentration}$
State the type of reaction when $[\text{CaEDTA}]^{2-}$ reacts with $\text{Cr}^{3+}(\text{aq})$, $\text{Fe}^{3+}(\text{aq})$ and $\text{Pb}^{2+}(\text{aq})$.
Deduce the relative concentrations of $[\text{CrEDTA}]^{-}$, $[\text{FeEDTA}]^{-}$ and $[\text{PbEDTA}]^{2-}$ present in the resulting mixture. Explain your answer.
The number of moles of water of crystallisation in a hydrated ionic salt can be found by titration using aqueous $\text{EDTA}^{4-}$ ions together with a suitable indicator. A $0.255\,\text{g}$ sample of hydrated chromium(III) sulfate, $\text{Cr}_2(\text{SO}_4)_3\cdot n\text{H}_2\text{O}$, is dissolved in water and diluted to $100\,\text{cm}^3$ in a volumetric flask. $25.0\,\text{cm}^3$ of this solution needs $26.2\,\text{cm}^3$ of $0.00800\,\text{mol dm}^{-3}$ aqueous $\text{EDTA}^{4-}$ ions to reach the end-point. The reaction takes place as shown: $[\text{Cr}(\text{H}_2\text{O})_6]^{3+} + \text{EDTA}^{4-} \rightarrow [\text{CrEDTA}]^{-} + 6\text{H}_2\text{O}$. Use the information given to calculate the value of $n$ in the formula of $\text{Cr}_2(\text{SO}_4)_3\cdot n\text{H}_2\text{O}$. Show your working.
A solution of $\text{Cr}^{3+}(aq)$ and a solution of $\text{Fe}^{3+}(aq)$ are different in colour. Explain why the two complexes have different colours.