Chemistry 9701 · AS & A Level · Group 2

Group 2 — practice question

(a(i))[3]

Describe the pattern in the thermal stabilities of the carbonates of the Group 2 elements. Explain your answer.

(a(ii))[1]

Copper(II) carbonate breaks down on heating in a similar manner to the carbonates of Group 2. Write an equation for the decomposition of copper(II) carbonate.

(b(i))[1]

Complete the electrons in boxes diagram in Fig. 1.1 to display the electronic configuration of a copper(II) ion.

(b(ii))[1]

There are five distinct $3d$ orbitals. Sketch the form of a $3d_{z^2}$ orbital in Fig. 1.2.

(b(iii))[1]

Copper can form stable complexes in the $+1$ and $+2$ oxidation states. Explain why transition elements show variable oxidation states.

(c(i))[2]

1,2-diaminoethane, $\text{H}_2\text{NCH}_2\text{CH}_2\text{NH}_2$, $en$, can function as a bidentate ligand. Explain what is meant by a bidentate ligand.

(c(ii))[3]

The complex $[\text{Cu(H}_2\text{O)}_2(en)_2]^{2+}$ exists as stereoisomers. Finish the three-dimensional diagrams in Fig. 1.3 to show the three stereoisomers of $[\text{Cu(H}_2\text{O)}_2(en)_2]^{2+}$. The $en$ ligand may be shown as N-N.

(c(iii))[1]

State the different types of stereoisomerism shown by $[\text{Cu(H}_2\text{O)}_2(en)_2]^{2+}$.

(c(iv))[1]

Identify one isomer from part (c)(ii) that is polar. Explain your answer.

(d(i))[1]

The mineral ore cryolite, $\text{Na}_3\text{AlF}_6$, contains one anion that is a complex ion. Complete Table 1.1 to suggest the formula of the complex ion and to identify the ligand present in $\text{Na}_3\text{AlF}_6$.

(d(ii))[4]

When a solution of $\text{Al}_2\text{O}_3$ in molten cryolite is electrolysed, aluminium metal forms at the cathode. The equation is shown: $\text{Al}^{3+} + 3\text{e}^- \rightarrow \text{Al}$. Calculate the maximum mass of aluminium produced when a current of $1.5\,\text{A}$ is passed through this solution for $30$ minutes. Give your answer to two significant figures.

Worked solution & mark scheme

This 19-mark question has a full step-by-step worked solution and mark scheme. One marking point: Thermal stability rises down the group from Mg to Ba OR the carbonates become more stable down the group from Mg to Ba

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