A Level Chemistry 9701 Paper 21, Oct/Nov 2024

The shorthand electronic configuration of cobalt is [Ar]$3{\text{d}}^{7}4{\text{s}}^2$. Identify what is meant by [Ar] by giving its full electronic configuration.

The lowest-energy electrons in cobalt are in the 1s orbital. Draw the shape of a 1s orbital.

Deduce the number of unpaired electrons in a cobalt atom.

Table 1.1 gives some details of the stable naturally occurring isotopes of rhodium and iridium. Table 1.1

Complete Table 1.1.

Table 1.2 shows the relative abundances of isotopes in a sample of an alloy containing rhodium and iridium only. Table 1.2

Define relative isotopic mass.

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 = ..............................

Hydrated rhodium(III) chloride, ${\text{RhCl}}_3\bullet x{\text{H}}_2\text{O}$, catalyses the conversion of ethene to but-2-ene. Both stereoisomers of but-2-ene are formed in the reaction. Hydrated rhodium(III) chloride contains 20.5% by mass of water of crystallisation. Deduce the integer value of $x$ in ${\text{RhCl}}_3\bullet x{\text{H}}_2\text{O}$. Show your working. $x$ = ..............................

Define stereoisomers.

Explain how the conversion of ethene to but-2-ene can be described as an addition reaction.

Draw the two stereoisomers of but-2-ene.

Describe the colours of the Group 17 elements, chlorine to iodine, at room temperature.

Describe the relative reactivity of the elements chlorine to iodine as oxidising agents.

State what is observed when chlorine reacts with hydrogen.

Explain why the thermal stability of the hydrogen halides decreases down the group.

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. Define free radical.

State the essential condition for chlorine to react with ${\text{C}}_2{\text{H}}_6$ at room temperature.

Write two equations to show the propagation steps in this reaction. 1 ........................................................................................................................................ 2 ........................................................................................................................................

${\text{CHCl}}_3$ is another halogenoalkane. ${\text{CHCl}}_3$ forms when propanone reacts with $\text{NaClO}$. $\text{NaClO}$ is made from chlorine in a disproportionation reaction. Identify a reagent and conditions that can be used to convert chlorine to $\text{NaClO}$.

Define disproportionation.

Write numbers in the boxes to balance the equation showing the reaction of propanone with $\text{NaClO}$. ${\text{CH}}_3{\text{COCH}}_3+\mathrm{\square }\text{NaClO}\to \mathrm{\square }{\text{CHCl}}_3+\mathrm{\square }{\text{CH}}_3\text{COONa}+\mathrm{\square }\text{NaOH}$

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.

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

Complete Table 3.1.

Identify the lattice structure shown by graphite.

Explain why Sn has good electrical conductivity.

Carbon is found in inorganic compounds such as carbonates. Write an equation for the reaction of magnesium carbonate with dilute $\text{HCl}(\text{aq})$.

Describe the thermal stability of the carbonates down Group 2.

Ammonium carbonate undergoes an acid–base reaction with $\text{NaOH}(\text{aq})$. Explain this statement.

Fig. 3.1 shows a sketch of some of the ionisation energies of silicon, Si. Complete the graph in Fig. 3.1 to show the third to sixth ionisation energies of Si.

Construct an equation to represent the second ionisation energy of Si.

Fig. 3.2 shows the boiling points of the simplest hydrides of the Group 14 elements, C to Pb. Explain the trend in the boiling points of the Group 14 hydrides shown in Fig. 3.2.

Deduce the shape of a molecule of ${\text{SiH}}_4$.

Silicon readily reacts with elements of high electronegativity. Write an equation for the formation of ${\text{SiCl}}_4$ from its constituent elements.

Describe what is observed when a small sample of ${\text{SiCl}}_4$ is added to water.

${\text{SiO}}_2$ is a white solid that melts above 1700°C. ${\text{SiCl}}_4$ 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.

Tin forms an amphoteric oxide, ${\text{SnO}}_2$. Suggest the formula of the tin compound that forms when ${\text{SnO}}_2$ reacts with ${\text{H}}_2{\text{SO}}_4$ in an acid–base reaction.

Reaction 1 is a nucleophilic addition reaction. 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.

Explain why A does not show optical isomerism.

Suggest the reagents and conditions for reaction 2.

Reaction 3 is a reduction reaction. Construct an equation to represent reaction 3. Use [H] to represent one atom of hydrogen from the reducing agent.

Name C.

State what is observed in reaction 4.

Explain why Fehling’s reagent does not react with propanone.

Compounds A, B and C can be distinguished using infrared spectroscopy. Fig. 4.3 shows the infrared spectrum of one of the compounds. Table 4.1 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.

Identify which of compounds A, B or C produces the infrared spectrum in Fig. 4.3. Explain your answer. compound .............................. explanation ........................................................................................................................ ........................................................................................................................................... ...........................................................................................................................................