A Level Chemistry 9701 Paper 43, May/June 2025

Write an equation for the thermal decomposition of ${\mathrm{C}\mathrm{a}\mathrm{C}\mathrm{O}}_3$.

State which of ${\mathrm{C}\mathrm{a}\mathrm{C}\mathrm{O}}_3$ and ${\mathrm{B}\mathrm{a}\mathrm{C}\mathrm{O}}_3$ decomposes at a lower temperature. Explain your answer. The compound that decomposes at a lower temperature is ................................................... explanation ...............................................................................................................................

Calcium oxide, $\mathrm{C}\mathrm{a}\mathrm{O}$, reacts with water to form compound A. Barium oxide, $\mathrm{B}\mathrm{a}\mathrm{O}$, reacts with water to form compound B. Identify A.

Explain why A is less soluble than B.

Under the conditions used in experiments 1 and 2, the value of $k$ is 26.4. The rate of the reaction is measured in $\mathrm{m}\mathrm{o}\mathrm{l}{\mathrm{d}\mathrm{m}}^{-3}{\mathrm{s}}^{-1}$. State the units of $k$. units of $k$ = ..............................

In experiment 1, the initial concentrations of $\mathrm{N}\mathrm{O}$ and ${\mathrm{C}\mathrm{l}}_2$ are equal. The initial rate of the reaction in experiment 1 is $2.57\times {10}^{-6}\mathrm{m}\mathrm{o}\mathrm{l}{\mathrm{d}\mathrm{m}}^{-3}{\mathrm{s}}^{-1}$. Calculate the initial concentration of $\mathrm{N}\mathrm{O}$. Show your working. initial concentration of $\mathrm{N}\mathrm{O}$ = .............................. $\mathrm{m}\mathrm{o}\mathrm{l}{\mathrm{d}\mathrm{m}}^{-3}$

In experiment 2, the initial concentrations of $\mathrm{N}\mathrm{O}$ and ${\mathrm{C}\mathrm{l}}_2$ are both ten times greater than the initial concentrations used in experiment 1. Calculate the initial rate of the reaction in experiment 2. initial rate of reaction in experiment 2 = .............................. $\mathrm{m}\mathrm{o}\mathrm{l}{\mathrm{d}\mathrm{m}}^{-3}{\mathrm{s}}^{-1}$

Experiment 3 uses a large excess of $\mathrm{N}\mathrm{O}$. The initial concentration of ${\mathrm{C}\mathrm{l}}_2$ is $2.00\times {10}^{-4}\mathrm{m}\mathrm{o}\mathrm{l}{\mathrm{d}\mathrm{m}}^{-3}$. The graph of $[{\mathrm{C}\mathrm{l}}_2]$ against time shows that the reaction has a constant half-life, $t_{1\mathrm{/}2}$. Explain this observation.

Under the conditions used in experiment 3, the value of the rate constant is 105.6. Show that $t_{1\mathrm{/}2}$ of $[{\mathrm{C}\mathrm{l}}_2]$ is $6.56\times {10}^{-3}\mathrm{s}$ under these conditions.

Calculate the time taken, in $\mathrm{s}$, for $[{\mathrm{C}\mathrm{l}}_2]$ to fall to $1.25\times {10}^{-5}\mathrm{m}\mathrm{o}\mathrm{l}{\mathrm{d}\mathrm{m}}^{-3}$ in experiment 3. time = .............................. $\mathrm{s}$

Sulfur dioxide, ${\mathrm{S}\mathrm{O}}_2$, reacts very slowly with oxygen in the atmosphere, forming sulfur trioxide, ${\mathrm{S}\mathrm{O}}_3$. This reaction is much faster in the presence of $\mathrm{N}\mathrm{O}$. Explain the role of $\mathrm{N}\mathrm{O}$ in this process. Include chemical equations in your answer.

Chromium(III) hydroxide, ${\mathrm{C}\mathrm{r}(\mathrm{O}\mathrm{H})}_3$, is only slightly soluble in water. The value of the solubility product, $K_{\mathrm{s}\mathrm{p}}$, of ${\mathrm{C}\mathrm{r}(\mathrm{O}\mathrm{H})}_3$ is $1.0\times {10}^{-33}$ at $298\mathrm{K}$. Complete the expression for $K_{\mathrm{s}\mathrm{p}}$ of ${\mathrm{C}\mathrm{r}(\mathrm{O}\mathrm{H})}_3$. Include the units. $K_{\mathrm{s}\mathrm{p}}=$ units = ..............................

Calculate the solubility, in $\mathrm{g}{\mathrm{d}\mathrm{m}}^{-3}$, of ${\mathrm{C}\mathrm{r}(\mathrm{O}\mathrm{H})}_3$ in pure water at $298\mathrm{K}$. Show your working. solubility = .............................. $\mathrm{g}{\mathrm{d}\mathrm{m}}^{-3}$

${\mathrm{C}\mathrm{r}(\mathrm{O}\mathrm{H})}_3$ is less soluble in $0.100\mathrm{m}\mathrm{o}\mathrm{l}{\mathrm{d}\mathrm{m}}^{-3}\mathrm{N}\mathrm{a}\mathrm{O}\mathrm{H}$ than it is in pure water. Explain this observation.

The value of the acid dissociation constant, $K_{\mathrm{a}}$, of butanoic acid, ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}$, is $1.51\times {10}^{-5}$ at $298\mathrm{K}$. Calculate the pH of $0.100\mathrm{m}\mathrm{o}\mathrm{l}{\mathrm{d}\mathrm{m}}^{-3}{\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}$ at $298\mathrm{K}$. Show your working. pH = ..............................

Calculate the pH of $0.100\mathrm{m}\mathrm{o}\mathrm{l}{\mathrm{d}\mathrm{m}}^{-3}\mathrm{N}\mathrm{a}\mathrm{O}\mathrm{H}$ at $298\mathrm{K}$. pH = ..............................

$5.00{\mathrm{c}\mathrm{m}}^3$ of $0.100\mathrm{m}\mathrm{o}\mathrm{l}{\mathrm{d}\mathrm{m}}^{-3}\mathrm{N}\mathrm{a}\mathrm{O}\mathrm{H}$ is added to $10.00{\mathrm{c}\mathrm{m}}^3$ of $0.100\mathrm{m}\mathrm{o}\mathrm{l}{\mathrm{d}\mathrm{m}}^{-3}$ ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}$. Calculate the pH of the resulting solution. Show your working. pH = ..............................

$80.0{\mathrm{c}\mathrm{m}}^3$ of an aqueous solution containing $0.704\mathrm{g}$ of ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}$ is shaken with $100{\mathrm{c}\mathrm{m}}^3$ of benzene, ${\mathrm{C}}_6{\mathrm{H}}_6$. There is $0.556\mathrm{g}$ of ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}$ in the $100{\mathrm{c}\mathrm{m}}^3$ of ${\mathrm{C}}_6{\mathrm{H}}_6$ at equilibrium. Calculate the partition coefficient, $K_{\mathrm{p}\mathrm{c}}$, of ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}$ between ${\mathrm{C}}_6{\mathrm{H}}_6$ and water. Show your working. $K_{\mathrm{p}\mathrm{c}}=$ ..............................

Define enthalpy change of hydration.

Explain the relative magnitudes of the enthalpy changes of hydration of ${\mathrm{K}}^{+}$ and ${\mathrm{C}\mathrm{a}}^{2+}$.

Define lattice energy.

The lattice energy, $\mathrm{\Delta }{H}_{\text{latt}}$, of calcium fluoride, ${\mathrm{C}\mathrm{a}\mathrm{F}}_2$, is $-2602\mathrm{k}\mathrm{J}{\mathrm{m}\mathrm{o}\mathrm{l}}^{-1}$. Calculate the enthalpy change of solution, $\mathrm{\Delta }{H}_{\text{sol}}$, in $\mathrm{k}\mathrm{J}{\mathrm{m}\mathrm{o}\mathrm{l}}^{-1}$, of ${\mathrm{C}\mathrm{a}\mathrm{F}}_2$. $\mathrm{\Delta }{H}_{\text{sol}}$ of ${\mathrm{C}\mathrm{a}\mathrm{F}}_2$ = .............................. $\mathrm{k}\mathrm{J}{\mathrm{m}\mathrm{o}\mathrm{l}}^{-1}$

The formation of ${\mathrm{C}\mathrm{a}\mathrm{F}}_2$ at $298\mathrm{K}$ is shown. $$\mathrm{C}\mathrm{a}(\mathrm{s})+{\mathrm{F}}_2(\mathrm{g})\to {\mathrm{C}\mathrm{a}\mathrm{F}}_2(\mathrm{s})\mathrm{\Delta }{H}^{\ominus }=-1214\mathrm{k}\mathrm{J}{\mathrm{m}\mathrm{o}\mathrm{l}}^{-1}$$ $$\mathrm{\Delta }{G}^{\ominus }=-1162\mathrm{k}\mathrm{J}{\mathrm{m}\mathrm{o}\mathrm{l}}^{-1}$$ Calculate the entropy change, $\mathrm{\Delta }{S}^{\ominus }$, in $\mathrm{J}{\mathrm{K}}^{-1}{\mathrm{m}\mathrm{o}\mathrm{l}}^{-1}$, for this reaction. $\mathrm{\Delta }{S}^{\ominus }=$ .............................. $\mathrm{J}{\mathrm{K}}^{-1}{\mathrm{m}\mathrm{o}\mathrm{l}}^{-1}$

Complete the electronic configurations of a ${\mathrm{C}\mathrm{u}}^{+}$ ion and a ${\mathrm{C}\mathrm{u}}^{2+}$ ion. ${\mathrm{C}\mathrm{u}}^{+}$ ion: $[\mathrm{A}\mathrm{r}]$ .............................. ${\mathrm{C}\mathrm{u}}^{2+}$ ion: $[\mathrm{A}\mathrm{r}]$ ..............................

Explain why transition elements have variable oxidation states.

Aqueous copper(II) sulfate, ${\mathrm{C}\mathrm{u}\mathrm{S}\mathrm{O}}_4$, contains the $[\mathrm{C}\mathrm{u}({\mathrm{H}}_2\mathrm{O}{)}_6{]}^{2+}$ complex ion. A few drops of ${\mathrm{N}\mathrm{H}}_3(\mathrm{a}\mathrm{q})$ are added to ${\mathrm{C}\mathrm{u}\mathrm{S}\mathrm{O}}_4(\mathrm{a}\mathrm{q})$. Describe any observations made.

Write an equation for the reaction taking place.

An excess of ${\mathrm{N}\mathrm{H}}_3(\mathrm{a}\mathrm{q})$ is added to ${\mathrm{C}\mathrm{u}\mathrm{S}\mathrm{O}}_4(\mathrm{a}\mathrm{q})$. Describe any further observations made.

Write an equation for the reaction taking place.

State the name for the type of reaction taking place.

Copper metal can be oxidised by acidified ${\mathrm{K}\mathrm{M}\mathrm{n}\mathrm{O}}_4$. The relevant half-equations and their standard electrode potentials, $E^{\ominus }$, are shown. $${\mathrm{C}\mathrm{u}}^{2+}+2{\mathrm{e}}^{-}\rightleftharpoons \mathrm{C}\mathrm{u}{E}^{\ominus }=+0.34\mathrm{V}$$ $${\mathrm{M}\mathrm{n}\mathrm{O}}_4^{-}+8{\mathrm{H}}^{+}+5{\mathrm{e}}^{-}\rightleftharpoons {\mathrm{M}\mathrm{n}}^{2+}+4{\mathrm{H}}_2\mathrm{O}{E}^{\ominus }=+1.52\mathrm{V}$$ A ${\mathrm{M}\mathrm{n}\mathrm{O}}_4^{-}\mathrm{/}{\mathrm{M}\mathrm{n}}^{2+}$ electrode is constructed using $0.0020\mathrm{m}\mathrm{o}\mathrm{l}{\mathrm{d}\mathrm{m}}^{-3}{\mathrm{M}\mathrm{n}\mathrm{O}}_4^{-}$, $1.0\mathrm{m}\mathrm{o}\mathrm{l}{\mathrm{d}\mathrm{m}}^{-3}{\mathrm{M}\mathrm{n}}^{2+}$ and $1.0\mathrm{m}\mathrm{o}\mathrm{l}{\mathrm{d}\mathrm{m}}^{-3}{\mathrm{H}}^{+}$. The temperature used is $298\mathrm{K}$. Use the Nernst equation to show that the $E$ value for this ${\mathrm{M}\mathrm{n}\mathrm{O}}_4^{-}\mathrm{/}{\mathrm{M}\mathrm{n}}^{2+}$ electrode is $+1.49\mathrm{V}$.

An electrochemical cell is constructed using a standard ${\mathrm{C}\mathrm{u}}^{2+}\mathrm{/}\mathrm{C}\mathrm{u}$ electrode and the ${\mathrm{M}\mathrm{n}\mathrm{O}}_4^{-}\mathrm{/}{\mathrm{M}\mathrm{n}}^{2+}$ electrode described in (d)(i). Calculate the value of $E_{\text{cell}}$. $E_{\text{cell}}=$ .............................. $\mathrm{V}$

Write an equation for the reaction taking place in the electrochemical cell described in (d)(ii).

Complete the sentences for the electrochemical cell described in (d)(ii). The .............................. electrode is the negative electrode. Electrons flow from the .............................. electrode to the .............................. electrode when the cell is in use.

A solution containing $[\mathrm{C}\mathrm{u}({\mathrm{H}}_2\mathrm{O}{)}_6{]}^{2+}$ is electrolysed for 5.00 hours using a constant electric current. $0.764\mathrm{g}$ of copper metal is formed at the cathode. No other reduction reaction takes place. Calculate the electric current, in $\mathrm{A}$, used. Give your answer to three significant figures. current = .............................. $\mathrm{A}$

Iron forms complex ions with the monodentate ligand, ${\mathrm{C}\mathrm{N}}^{-}$. Complex ion A contains one ${\mathrm{F}\mathrm{e}}^{3+}$ ion and six ${\mathrm{C}\mathrm{N}}^{-}$ ligands. Complex ion B contains one ${\mathrm{F}\mathrm{e}}^{2+}$ ion and six ${\mathrm{C}\mathrm{N}}^{-}$ ligands. State the formulae of these two complex ions. Include the overall charge of each complex ion. complex ion A ................................................. complex ion B .................................................

Explain why a solution containing complex ion A and a solution containing complex ion B are different colours.

In complex ion A, the carbon atom of each ${\mathrm{C}\mathrm{N}}^{-}$ ligand bonds to the ${\mathrm{F}\mathrm{e}}^{3+}$ ion. State the type of bonding involved.

Complex ions have different geometries. Complex ion A is octahedral. ${\mathrm{A}\mathrm{g}}^{+}$ ions form a linear complex with ammonia. $\mathrm{N}\mathrm{i}$ atoms form a tetrahedral complex with carbon monoxide molecules. The carbon atom in the monodentate carbon monoxide ligand bonds to the nickel atom. ${\mathrm{P}\mathrm{d}}^{2+}$ ions form a square planar complex with chloride ions. Complete Fig. 6.1 to show the geometry of each of these four ions, using three-dimensional bonds where necessary. Label one bond angle on each complex ion.

Give the systematic name of E.

The proton (${}^1\mathrm{H}$) NMR spectra of D and E are compared. They are very similar. The proton (${}^1\mathrm{H}$) NMR spectrum of D is shown in Fig. 7.2. Suggest a suitable solvent for obtaining the spectrum in Fig. 7.2.

The proton (${}^1\mathrm{H}$) NMR spectrum of E is obtained twice, once before and once after shaking with ${\mathrm{D}}_2\mathrm{O}$. Describe any differences between these two spectra. Explain your answer.

Complete Table 7.1 for the proton (${}^1\mathrm{H}$) NMR spectrum of D.

Compounds D and E can be distinguished by carbon-13 NMR spectroscopy. State the number of peaks in each spectrum. The carbon-13 NMR spectrum of D has .............................. peaks. The carbon-13 NMR spectrum of E has .............................. peaks.

Compound D can be oxidised to compound F by alkaline ${\mathrm{K}\mathrm{M}\mathrm{n}\mathrm{O}}_4$ followed by dilute acid. Write an equation for this reaction using molecular formulae for D and F. The products of this reaction are F, water and carbon dioxide. Use [O] to represent one atom of oxygen from the oxidising agent.

F reacts with an excess of ${\mathrm{S}\mathrm{O}\mathrm{C}\mathrm{l}}_2$ to form compound G. The molecular formula of G is ${\mathrm{C}}_8{\mathrm{H}}_4{\mathrm{C}\mathrm{l}}_2{\mathrm{O}}_2$. G reacts with ethane-1,2-diol, ${\mathrm{H}\mathrm{O}\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2\mathrm{O}\mathrm{H}$, to form a mixture of products that includes compounds J, molecular formula ${\mathrm{C}}_{10}{\mathrm{H}}_8{\mathrm{O}}_4$, and K, molecular formula ${\mathrm{C}}_{18}{\mathrm{H}}_{12}{\mathrm{C}\mathrm{l}}_2{\mathrm{O}}_6$. Draw the structures of compounds G, J and K in Fig. 7.4.

The mechanism for the reaction involves methylbenzene reacting with a ${\mathrm{B}\mathrm{r}}^{+}$ ion. This ion is produced when bromine reacts with the catalyst. Complete the equation for the reaction of ${\mathrm{B}\mathrm{r}}_2$ with the catalyst. $${\mathrm{B}\mathrm{r}}_2+\text{..............................}\to {\mathrm{B}\mathrm{r}}^{+}+\text{..............................}$$

One of the isomers of L forms in much smaller amounts than the other two isomers. Draw the structure of this isomer and explain why it forms in the smallest amount.

Complete the mechanism in Fig. 8.1 for the reaction between methylbenzene and the ${\mathrm{B}\mathrm{r}}^{+}$ ion. Include all relevant curly arrows and charges.

Chlorobutane and chlorobenzene are added separately to samples of warm aqueous ${\mathrm{A}\mathrm{g}\mathrm{N}\mathrm{O}}_3$. One of the chloro-compounds reacts slowly and the other does not react. Identify the chloro-compound that reacts and describe any observations.

Write two equations to explain any observations in (b)(i).

Explain the difference in reactivity of chlorobutane and chlorobenzene with warm aqueous ${\mathrm{A}\mathrm{g}\mathrm{N}\mathrm{O}}_3$.

Phenylamine, ${\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{N}\mathrm{H}}_2$, and propylamine, ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2{\mathrm{N}\mathrm{H}}_2$, can be produced by different reduction reactions. Identify an organic compound that can be converted into ${\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{N}\mathrm{H}}_2$ by a reduction reaction. State the reagents and conditions for this reaction. organic compound ............................................................................................................. reagents ............................................................................................................................ conditions ..........................................................................................................................

Identify an organic compound that can be converted into ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2{\mathrm{N}\mathrm{H}}_2$ by a reduction reaction. State the reagent for this reaction. organic compound ............................................................................................................. reagent ..............................................................................................................................

Identify a single test that will distinguish between ${\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{N}\mathrm{H}}_2$ and ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2{\mathrm{N}\mathrm{H}}_2$ by producing a white precipitate with only one of these amines. Draw the structure of the compound that is precipitated. testing reagent .................................................................................................................. amine that gives a precipitate ........................................................................................... structure of the compound that is precipitated:

Describe the relative basicities of ${\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{N}\mathrm{H}}_2$, ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2{\mathrm{N}\mathrm{H}}_2$ and ${\mathrm{N}\mathrm{H}}_3$. Explain your answer. .............................................. < .............................................. < .............................................. least basic $$ most basic

Draw the displayed formula of ethanedioic acid.

The three acids, propanoic acid, methanoic acid and ethanedioic acid, can be distinguished using a combination of two chemical tests. Neither testing reagent is an acid–base indicator. Identify two suitable testing reagents and complete Table 10.1 to show the observations from each test. reagent 1 ........................................................ reagent 2 ........................................................

When propanoic acid is treated with chlorine gas in the presence of ultraviolet light, a mixture of products is formed. One of these products is 2,2-dichloropropanoic acid. Explain why 2,2-dichloropropanoic acid is stronger than propanoic acid. Refer to the structure of each compound in your answer.