A Level Chemistry 9701 Paper 23, May/June 2026

Complete Table 1.1. Table 1.1

Write an equation for the reaction of ${\mathrm{P}\mathrm{C}\mathrm{l}}_5$ with an excess of cold water.

The reaction of chlorine with cold water is used in water purification. Write an equation for the reaction of chlorine with cold water.

Explain the use of chlorine in water purification.

The relative strength of ${\mathrm{C}\mathrm{l}}_2$, ${\mathrm{B}\mathrm{r}}_2$ and ${\mathrm{I}}_2$ as oxidising agents can be compared by adding $\mathrm{N}\mathrm{a}\mathrm{B}\mathrm{r}(\mathrm{a}\mathrm{q})$ to separate samples of ${\mathrm{C}\mathrm{l}}_2$ and ${\mathrm{I}}_2$. Describe the relative reactivity of ${\mathrm{C}\mathrm{l}}_2$, ${\mathrm{B}\mathrm{r}}_2$ and ${\mathrm{I}}_2$ as oxidising agents.

Complete Table 1.2 to describe the reactions of $\mathrm{N}\mathrm{a}\mathrm{B}\mathrm{r}(\mathrm{a}\mathrm{q})$ with separate samples of ${\mathrm{C}\mathrm{l}}_2(\mathrm{a}\mathrm{q})$ and ${\mathrm{I}}_2(\mathrm{a}\mathrm{q})$. Table 1.2

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 ${\mathrm{N}\mathrm{H}}_3(\mathrm{a}\mathrm{q})$ .......................................................................................

Use Table 2.1 to describe and explain the variation in atomic radius down Group 18.

Identify one Group 18 element from Table 2.1 that behaves most like an ideal gas under standard conditions. Explain your answer.

A sample of $1.775\mathrm{g}$ of gas $\mathbf{X}$ occupies $617.0{\mathrm{c}\mathrm{m}}^3$ at $300\mathrm{K}$ and $101\mathrm{k}\mathrm{P}\mathrm{a}$. Calculate the relative molecular mass, $M_{\mathrm{r}}$, of $\mathbf{X}$ assuming that $\mathbf{X}$ behaves as an ideal gas. $M_{\mathrm{r}}$ of $\mathbf{X}=$ .........................................................

Complete Figure 3.1 to show the reaction pathway diagram for reaction 1. Draw arrows to represent the enthalpy change, $\mathrm{\Delta }H$, and activation energy, $E_{\mathrm{A}}$.

Define Le Chatelier's principle.

In industry, reaction 1 occurs at $400\text{–}450{}^{\circ }\mathrm{C}$ and $110\text{–}200\mathrm{k}\mathrm{P}\mathrm{a}$ with a catalyst. Complete Table 3.1 by using the terms 'increase', 'decrease' or 'no change'. Table 3.1

A sealed tube that initially contains only $2.00\mathrm{m}\mathrm{o}\mathrm{l}$ of ${\mathrm{S}\mathrm{O}}_2(\mathrm{g})$ and $2.00\mathrm{m}\mathrm{o}\mathrm{l}$ of ${\mathrm{O}}_2(\mathrm{g})$ is left to reach equilibrium. At equilibrium, $1.96\mathrm{m}\mathrm{o}\mathrm{l}$ of ${\mathrm{S}\mathrm{O}}_3(\mathrm{g})$ is present and the total pressure is $150\mathrm{k}\mathrm{P}\mathrm{a}$. reaction 1 $2{\mathrm{S}\mathrm{O}}_2(\mathrm{g})+{\mathrm{O}}_2(\mathrm{g})\rightleftharpoons 2{\mathrm{S}\mathrm{O}}_3(\mathrm{g})$ Complete Table 3.2. Table 3.2

Table 3.3 shows the mole fractions at equilibrium of ${\mathrm{S}\mathrm{O}}_2(\mathrm{g})$, ${\mathrm{O}}_2(\mathrm{g})$ and ${\mathrm{S}\mathrm{O}}_3(\mathrm{g})$ under different conditions. Table 3.3

Calculate $K_{\mathrm{p}}$ at $200\mathrm{k}\mathrm{P}\mathrm{a}$ using the data from Table 3.3. Include units in your answer. $K_{\mathrm{p}}=$ ............................................................... units ...............................................................

Complete Table 4.1. Table 4.1

Complete Table 4.2 to show what is observed when separate samples of $\mathbf{V}$ are added to each reagent. State 'none' if no reaction occurs. Table 4.2

Suggest why Fehling's reagent does not react with $\mathbf{V}$ but does react with aldehyde functional groups.

Figure 4.1 is repeated for use in 4(b). $\mathbf{V}$ is completely oxidised by heating under reflux with an excess of acidified ${\mathrm{K}}_2{\mathrm{C}\mathrm{r}}_2{\mathrm{O}}_7(\mathrm{a}\mathrm{q})$ to produce organic compound $\mathbf{Z}$. Describe the colour change in this reaction. colour of mixture at start of the reaction ............................................................................ colour of mixture after the reaction ....................................................................................

Draw the structure of $\mathbf{Z}$.

Compounds $\mathbf{W}$, $\mathbf{X}$ and $\mathbf{Y}$ are structural isomers of $\mathbf{V}$. Describe structural isomerism.

Identify which of structures $\mathbf{V}$, $\mathbf{W}$, $\mathbf{X}$ and $\mathbf{Y}$ show stereoisomerism. Explain your answer by referring to the relevant parts of the molecule that cause stereoisomerism.

$\mathbf{Y}$ reacts with reagent $\mathbf{R}$ to produce compound $\mathbf{E}$. Name reagent $\mathbf{R}$.

Exactly $0.03\mathrm{m}\mathrm{o}\mathrm{l}$ of one of the isomers, $\mathbf{V}$, $\mathbf{W}$, $\mathbf{X}$ or $\mathbf{Y}$, is completely oxidised by $0.08\mathrm{m}\mathrm{o}\mathrm{l}$ of acidified ${\mathrm{K}}_2{\mathrm{C}\mathrm{r}}_2{\mathrm{O}}_7(\mathrm{a}\mathrm{q})$ to produce only one organic compound with molecular formula ${\mathrm{C}}_5{\mathrm{H}}_4{\mathrm{O}}_8$. Identify which isomer, $\mathbf{V}$, $\mathbf{W}$, $\mathbf{X}$ or $\mathbf{Y}$, is used in this reaction.

Complete the equation for this reaction. $3{\mathrm{C}}_5{\mathrm{H}}_{12}{\mathrm{O}}_4+\text{.....}{\mathrm{C}\mathrm{r}}_2{\mathrm{O}}_7^{2-}+\text{.....}{\mathrm{H}}^{+}\to 3{\mathrm{C}}_5{\mathrm{H}}_4{\mathrm{O}}_8+\text{.....}{\mathrm{C}\mathrm{r}}^{3+}+\text{.....}{\mathrm{H}}_2\mathrm{O}$

Complete Table 5.1.

Name the mechanism for the reaction of propane and ${\mathrm{C}\mathrm{l}}_2(\mathrm{g})$ in the presence of ultraviolet light.

The mechanism for this reaction involves three stages. stage 1 initiation stage 2 propagation stage 3 termination During the initiation reaction, a chlorine free radical is produced. Complete Figure 5.1 to describe the arrangement of electrons in a chlorine free radical.

Suggest a reaction sequence of two propagation reactions that result in ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_3$ forming ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2\mathrm{C}\mathrm{l}$. propagation reaction 1 ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_3$ ............................................. $\to$ ................................................................. propagation reaction 2 ................................................................... $\to {\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2\mathrm{C}\mathrm{l}$ ........................................

Suggest a reaction sequence of one propagation reaction followed by a termination reaction that results in ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_3$ forming $({\mathrm{C}\mathrm{H}}_3{)}_2\mathrm{C}\mathrm{H}\mathrm{C}\mathrm{H}({\mathrm{C}\mathrm{H}}_3{)}_2$. propagation reaction 3 ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_3$ ......................................... $\to$ ..................................................................... termination reaction ............................................................... $\to ({\mathrm{C}\mathrm{H}}_3{)}_2\mathrm{C}\mathrm{H}\mathrm{C}\mathrm{H}({\mathrm{C}\mathrm{H}}_3{)}_2$

Compound $\mathbf{A}$ has the molecular formula ${\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{l}}_2$. Figure 5.2 shows the mass spectrum of $\mathbf{A}$. Explain the difference in relative abundance of the peaks at $m\mathrm{/}e=35$ and $m\mathrm{/}e=37$.

Complete Table 5.2. Table 5.2