AS & A Level Chemistry - 9701 Paper 2 2024 Winter Zone 1

Cobalt, rhodium and iridium are metals in the same group of the Periodic Table.
(a) The shorthand electronic configuration of cobalt is [Ar]3d\(^7\)4s\(^2\).
(i) Identify what is meant by [Ar] by giving its full electronic configuration.
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[1]
(ii) The lowest-energy electrons in cobalt are in the 1s orbital.
Draw the shape of a 1s orbital.

[1]
(iii) Deduce the number of unpaired electrons in a cobalt atom.
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[1]
(b) Table 1.1 gives some details of the stable naturally occurring isotopes of rhodium and iridium.
[Table_1]
Complete Table 1.1.
[3]
(c) Table 1.2 shows the relative abundances of isotopes in a sample of an alloy containing rhodium and iridium only.
[Table_2]
(i) Define relative isotopic mass.
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[2]
(ii) Use Table 1.2 to calculate the relative atomic mass, A\(_r\), of iridium in the alloy.
Give your answer to two decimal places.
relative atomic mass of iridium = ................................
[2]
(d) Hydrated rhodium(III) chloride, RhCl\(_3\)·xH\(_2\)O, catalyses the conversion of ethene to but-2-ene.
Both stereoisomers of but-2-ene are formed in the reaction.
(i) Hydrated rhodium(III) chloride contains 20.5% by mass of water of crystallisation.
Deduce the integer value of x in RhCl\(_3\)·xH\(_2\)O.
Show your working.
x = ................................
[2]
(ii) Define stereoisomers.
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[1]
(iii) Explain how the conversion of ethene to but-2-ene can be described as an addition reaction.
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[1]
(iv) Draw the two stereoisomers of but-2-ene.

[2]

Chlorine is one of the elements in Group 17 of the Periodic Table.

(a) (i) Describe the colours of the Group 17 elements, chlorine to iodine, at room temperature.
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(ii) Describe the relative reactivity of the elements chlorine to iodine as oxidising agents.
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(iii) State what is observed when chlorine reacts with hydrogen.
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(iv) Explain why the thermal stability of the hydrogen halides decreases down the group.
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(b) The halogenoalkane $\text{CH}_3\text{CH}_2\text{Cl}$ forms when chlorine reacts with $\text{C}_2\text{H}_6$ via a free-radical substitution mechanism.
(i) Define free radical.
........................................................................................................................................... [1]
(ii) State the essential condition for chlorine to react with $\text{C}_2\text{H}_6$ at room temperature.
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(iii) Write \textbf{two} equations to show the propagation steps in this reaction.
1 .........................................................................................................................................
2 ......................................................................................................................................... [2]

(c) $\text{CHCl}_3$ is another halogenoalkane. $\text{CHCl}_3$ forms when propanone reacts with $\text{NaClO}$.

$\text{NaClO}$ is made from chlorine in a disproportionation reaction.

(i) Identify a reagent and conditions that can be used to convert chlorine to $\text{NaClO}$.
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(ii) Define disproportionation.
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(iii) Write numbers in the boxes to balance the equation showing the reaction of propanone with $\text{NaClO}$.
\[ \text{CH}_3\text{COCH}_3 + \boxed{\text{}} \text{NaClO} \rightarrow \boxed{\text{}} \text{CHCl}_3 + \boxed{\text{}} \text{CH}_3\text{COONa} + \boxed{\text{}} \text{NaOH} \] [1]

(iv) Aqueous $\text{AgNO}_3$ dissolved in ethanol reacts with an aqueous solution of $\text{CHCl}_3$.
State what is observed in this reaction. Explain your answer.
............................................................................................................................................................... [2]

(a) Table 3.1 shows some properties of two Group 14 elements, C and Sn, in their standard states. The table is incomplete.

\begin{table} \centering \begin{tabular}{|c|c|c|} \hline & C (graphite) & Sn \\ \hline state and appearance & grey shiny solid & silvery solid \\ in standard state & & \\ \hline electrical conductivity & & good \\ \hline type of bonding & & metallic \\ \hline type of structure & giant & \\ \hline \end{tabular} \end{table}

(i) Complete Table 3.1.
(ii) Identify the lattice structure shown by graphite.
....................................................................................................... [1]
(iii) Explain why Sn has good electrical conductivity.
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(b) Carbon is found in inorganic compounds such as carbonates.
(i) Write an equation for the reaction of magnesium carbonate with dilute HCl(aq).
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(ii) Describe the thermal stability of the carbonates down Group 2.
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(iii) Ammonium carbonate undergoes an acid–base reaction with NaOH(aq).
Explain this statement.
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(c) Fig. 3.1 shows a sketch of some of the ionisation energies of silicon, Si.

[Figure_3.1]

(i) Complete the graph in Fig. 3.1 to show the third to sixth ionisation energies of Si. [2]
(ii) Construct an equation to represent the second ionisation energy of Si.
....................................................................................................... [1]

(d) Fig. 3.2 shows the boiling points of the simplest hydrides of the Group 14 elements, C to Pb.

[Figure_3.2]

(i) Explain the trend in the boiling points of the Group 14 hydrides shown in Fig. 3.2.
....................................................................................................... [2]
(ii) Deduce the shape of a molecule of SiH$_4$.
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(e) Silicon readily reacts with elements of high electronegativity.
(i) Write an equation for the formation of SiCl$_4$ from its constituent elements.
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(ii) Describe what is observed when a small sample of SiCl$_4$ is added to water.
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(iii) SiO$_2$ is a white solid that melts above 1700$^\circ$C.
SiCl$_4$ is a colourless liquid at room temperature.
Explain the difference in the melting points of these two compounds with reference to their structure and bonding.
....................................................................................................... [2]

(f) Tin forms an amphoteric oxide, SnO$_2$.
Suggest the formula of the tin compound that forms when SnO$_2$ reacts with H$_2$SO$_4$ in an acid–base reaction.
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Propanope, CH₃COCH₃, is an important organic reagent. Fig. 4.1 shows some reactions of propanone and its derivatives.

[Image_1: Fig. 4.1 with reactions of propanone and its derivatives]

(a) Reaction 1 is a nucleophilic addition reaction.
(i) Complete Fig. 4.2 to show the mechanism for the formation of A from propanone. Include charges, dipoles, lone pairs of electrons and curly arrows as appropriate.

[Image_2: Fig. 4.2 with propanone mechanism]
[3 marks]

(ii) Explain why A does not show optical isomerism. ........................................................................................................................................ [1 mark]

(b) Suggest the reagents and conditions for reaction 2. ........................................................................................................................................ [1 mark]

(c) Reaction 3 is a reduction reaction.
(i) Construct an equation to represent reaction 3. Use [H] to represent one atom of hydrogen from the reducing agent. ........................................................................................................................................ [1 mark]
(ii) Name C. ........................................................................................................................................ [1 mark]

(d) State what is observed in reaction 4. ........................................................................................................................................ [1 mark]

(e) Explain why Fehling’s reagent does not react with propanone. ........................................................................................................................................ [1 mark]

(f) Compounds A, B and C can be distinguished using infrared spectroscopy.
Fig. 4.3 shows the infrared spectrum of one of the compounds.

[Image_3: Fig. 4.3 with infrared spectrum]

Table 4.1
| bond | functional groups containing the bond | characteristic infrared absorption range (in wavenumbers) / cm⁻¹ |
| --- | --- | --- |
| C–O | hydroxy, ester | 1040–1300 |
| C=C | aromatic compound, alkene | 1500–1680 |
| C=O | amide | 1640–1690 |
| | carbonyl, carboxyl | 1670–1740 |
| | ester | 1710–1750 |
| C≡N | nitrile | 2220–2250 |
| C–H | alkane | 2850–2950 |
| N–H | amine, amide | 3300–3500 |
| O–H | carboxyl, hydroxy | 2500–3000, 3200–3600 |

(i) Explain why the absorptions at 2850–2950 cm⁻¹ are not useful to help determine which of the compounds A, B or C produces the infrared spectrum in Fig. 4.3. Use Table 4.1 to answer this question. ........................................................................................................................................ [1 mark]

(ii) Identify which of compounds A, B or C produces the infrared spectrum in Fig. 4.3. Explain your answer.
compound ...........................
explanation ........................................................................................................................................ ........................................................................................................................................ [1 mark]

[Total: 11 marks]