A Level Chemistry 9701 Paper 21, May/June 2026

Complete the dot-and-cross diagram in Figure 1.1 to show the arrangement of outer shell electrons in a molecule of ${\mathrm{S}\mathrm{F}}_6$.

Name the shape of a molecule of ${\mathrm{S}\mathrm{F}}_6$.

Table 1.1 shows information about sulfur and chlorine. Table 1.1

Name the orbital that contains the lowest energy electron in an atom of sulfur. Draw the shape of this orbital. name ................................................................................................................................. shape

Construct an equation to represent the first ionisation energy of chlorine.

Explain the difference in the values of first ionisation energy of sulfur and chlorine in Table 1.1.

A molecule of ${\mathrm{S}\mathrm{C}\mathrm{l}}_2$ is polar. Predict bond angle $x$ in Figure 1.2 using VSEPR theory. Explain your answer. bond angle $x$ = ..............................° explanation ........................................................................................................................ ........................................................................................................................................... ...........................................................................................................................................

Show on Figure 1.3 all the dipoles present in the molecule of ${\mathrm{S}\mathrm{C}\mathrm{l}}_2$.

${\mathrm{S}\mathrm{C}\mathrm{l}}_2$ and ${\mathrm{H}}_2\mathrm{O}$ both contain instantaneous dipole–induced dipole attractions and permanent dipole attractions. Complete Table 1.2. Table 1.2

Identify which molecule, ${\mathrm{S}\mathrm{C}\mathrm{l}}_2$ or ${\mathrm{H}}_2\mathrm{O}$, has the stronger instantaneous dipole–induced dipole attractions. Explain your answer.

${\mathrm{H}}_2\mathrm{O}$ has a greater dipole moment than ${\mathrm{S}\mathrm{C}\mathrm{l}}_2$. Explain why.

Compound X contains sulfur and chlorine only. $100.0\mathrm{g}$ of X contains $47.49\mathrm{g}$ of sulfur. The relative molecular mass, $M_{\mathrm{r}}$, of X is $135.2$. Determine the molecular formula of X. Show your working. molecular formula of X = .........................................................

Write an overall equation for stage 3.

The reaction conditions for stage 2 include: • using a ratio of $1\mathrm{m}\mathrm{o}\mathrm{l}{\mathrm{S}\mathrm{O}}_2$ to $1\mathrm{m}\mathrm{o}\mathrm{l}{\mathrm{O}}_2$ • heat in the presence of ${\mathrm{V}}_2{\mathrm{O}}_5$. Stage 2 is repeated using a ratio of more than $1\mathrm{m}\mathrm{o}\mathrm{l}{\mathrm{S}\mathrm{O}}_2$ to $1\mathrm{m}\mathrm{o}\mathrm{l}{\mathrm{O}}_2$. Predict the effect on the percentage yield of ${\mathrm{S}\mathrm{O}}_3$ at equilibrium. Use Le Chatelier’s Principle to explain your answer.

Explain how ${\mathrm{V}}_2{\mathrm{O}}_5$ affects the rate of reaction.

${\mathrm{C}\mathrm{a}\mathrm{C}\mathrm{O}}_3$ and ${\mathrm{O}}_2$ are added to the waste gases from the Contact process before they escape. This prevents the release of ${\mathrm{S}\mathrm{O}}_2$ into the atmosphere. equation 1 $2{\mathrm{C}\mathrm{a}\mathrm{C}\mathrm{O}}_3+2{\mathrm{S}\mathrm{O}}_2+{\mathrm{O}}_2\to 2{\mathrm{C}\mathrm{a}\mathrm{S}\mathrm{O}}_4+2{\mathrm{C}\mathrm{O}}_2$ State one environmental consequence of the release of ${\mathrm{S}\mathrm{O}}_2(\mathrm{g})$ into the atmosphere.

Use the ideal gas equation to calculate the volume of ${\mathrm{O}}_2(\mathrm{g})$ that reacts with $0.500\mathrm{m}\mathrm{o}\mathrm{l}$ of ${\mathrm{S}\mathrm{O}}_2$ at $400{}^{\circ }\mathrm{C}$ and $101\mathrm{k}\mathrm{P}\mathrm{a}$ in equation 1. Include units in your answer. volume of ${\mathrm{O}}_2(\mathrm{g})$ = ............................................................... units ...............................................................

Write an equation for reaction 1.

Identify the reactant that behaves as a Brønsted–Lowry base in reaction 1.

State the formulae of the species responsible for the brown vapour in reaction 2 and for the purple vapour in reaction 3. brown vapour ............................................................... purple vapour ...............................................................

Explain why reaction 3 produces purple vapour.

Complete Table 3.2. Table 3.2

Explain why reaction 3 produces ${\mathrm{H}}_2\mathrm{S}$ but reaction 2 does not produce ${\mathrm{H}}_2\mathrm{S}$.

Describe what is observed when ${\mathrm{A}\mathrm{g}}^{+}(\mathrm{a}\mathrm{q})$, followed by ${\mathrm{N}\mathrm{H}}_3(\mathrm{a}\mathrm{q})$, are added to a sample of $\mathrm{N}\mathrm{a}\mathrm{I}(\mathrm{a}\mathrm{q})$. observation after addition of ${\mathrm{A}\mathrm{g}}^{+}(\mathrm{a}\mathrm{q})$ ................................................................................. observation after addition of ${\mathrm{N}\mathrm{H}}_3(\mathrm{a}\mathrm{q})$ ................................................................................

Write an ionic equation for the reaction of ${\mathrm{A}\mathrm{g}}^{+}(\mathrm{a}\mathrm{q})$ with $\mathrm{N}\mathrm{a}\mathrm{I}(\mathrm{a}\mathrm{q})$.

Compound Z is oxidised to produce organic compound W, ${\mathrm{C}}_5{\mathrm{H}}_6{\mathrm{O}}_7$, by heating under reflux with an excess of acidified ${\mathrm{C}\mathrm{r}}_2{\mathrm{O}}_7^{2-}(\mathrm{a}\mathrm{q})$. Describe the colour change in this reaction. colour of mixture at start of the reaction ............................................................................ colour of mixture after the reaction ....................................................................................

The complete oxidation of $0.025\mathrm{m}\mathrm{o}\mathrm{l}$ of Z requires $0.050\mathrm{m}\mathrm{o}\mathrm{l}$ of ${\mathrm{C}\mathrm{r}}_2{\mathrm{O}}_7^{2-}(\mathrm{a}\mathrm{q})$. W is produced in this reaction. Balance the equation for this reaction. .....${\mathrm{C}}_5{\mathrm{H}}_{12}{\mathrm{O}}_4$ + .....${\mathrm{C}\mathrm{r}}_2{\mathrm{O}}_7^{2-}$ + .....${\mathrm{H}}^{+}$ $\to$ .....${\mathrm{C}}_5{\mathrm{H}}_6{\mathrm{O}}_7$ + .....${\mathrm{C}\mathrm{r}}^{3+}$ + .....${\mathrm{H}}_2\mathrm{O}$

Compound A is a structural isomer of Z. Complete Table 4.1 to show what is observed when separate samples of A are added to each reagent. State ‘none’ if no reaction occurs. Table 4.1

Suggest why Fehling’s reagent does not react with A but does react with aldehyde functional groups.

Compound A is heated under reflux with an excess of acidified ${\mathrm{C}\mathrm{r}}_2{\mathrm{O}}_7^{2-}(\mathrm{a}\mathrm{q})$ to produce organic compound Y. Draw the structure of Y.

Compound B reacts with an excess of ${\mathrm{L}\mathrm{i}\mathrm{A}\mathrm{l}\mathrm{H}}_4$ to produce organic compound C. Complete the equation in Figure 4.3 to show the reaction of B with an excess of ${\mathrm{L}\mathrm{i}\mathrm{A}\mathrm{l}\mathrm{H}}_4$ to produce C. [H] represents one atom of hydrogen from the reducing agent, ${\mathrm{L}\mathrm{i}\mathrm{A}\mathrm{l}\mathrm{H}}_4$.

Complete Table 5.1. Table 5.1

In reaction 1, ethene reacts with ${\mathrm{C}\mathrm{l}}_2(\mathrm{g})$ at room temperature. Name the mechanism for reaction 1.

Describe what is meant by heterolytic fission of a covalent bond.

Complete Figure 5.2 to show the mechanism for the reaction of ethene with ${\mathrm{C}\mathrm{l}}_2$ in reaction 1. Include charges, dipoles, lone pairs of electrons and curly arrows, as appropriate.

When 1,2-dichloroethane is heated in reaction 2, thermal decomposition occurs. The reaction is endothermic. State the type of reaction that occurs.

Draw the repeat unit of poly(chloroethene).

Figure 5.3 shows the mass spectrum of chloroethene. Identify the species responsible for the peaks at $m\mathrm{/}e=64$ and $m\mathrm{/}e=27$. peak at $m\mathrm{/}e=64$ .............................................................................................................. peak at $m\mathrm{/}e=27$ ..............................................................................................................

Explain the difference in relative abundance of the peaks at $m\mathrm{/}e=62$ and $m\mathrm{/}e=64$.