May/June 2010

What proton number could an element have if each of its atoms has three unpaired electrons?

Atomic structure

The table shows the concentrations and pH values for the aqueous solutions of two compounds, X and Y. Either compound may be an acid or a base. For X: concentration $2\,\text{mol dm}^{-3}$, pH $6$. For Y: concentration $2\,\text{mol dm}^{-3}$, pH $9$. Student P concluded that X is a strong acid. Student Q concluded that the extent of dissociation is lower in X(aq) than in Y(aq). Which of the students are correct?

Equilibria

The water in a swimming pool can be kept free from harmful bacteria by adding aqueous sodium chlorate(I), $\text{NaOCl}$. This then reacts with water to form $\text{HOCl}$ molecules that kill bacteria. $\text{OCl}^-(aq) + \text{H}_2\text{O} \rightleftharpoons \text{OH}^-(aq) + \text{HOCl}(aq)$ Under strong sunlight, the $\text{OCl}^-$ ion is decomposed by ultra-violet light. $\text{OCl}^-(aq) + \text{UV light} \rightarrow \text{Cl}^-(aq) + \tfrac{1}{2}\text{O}_2(g)$ Which method would keep the concentration of $\text{HOCl}(aq)$ at the highest level?

Equilibria

$\text{Na}_2\text{S}_2\text{O}_3$ reacts with dilute $\text{HCl}$, producing a pale yellow precipitate. When $1\,\text{cm}^3$ of $0.1\,\text{mol dm}^{-3}$ $\text{HCl}$ is mixed with $10\,\text{cm}^3$ of $0.02\,\text{mol dm}^{-3}$ $\text{Na}_2\text{S}_2\text{O}_3$, the precipitate appears slowly. When the experiment is repeated using $1\,\text{cm}^3$ of $0.1\,\text{mol dm}^{-3}$ $\text{HCl}$ and $10\,\text{cm}^3$ of $0.05\,\text{mol dm}^{-3}$ $\text{Na}_2\text{S}_2\text{O}_3$, the precipitate appears more quickly. What is the reason for this?

Reaction kinetics

What occurs when concentrated sulfuric acid reacts with sodium chloride?

Group 17

X is a salt containing one of the halogens chlorine, bromine, iodine, or astatine (proton number $85$). The reaction scheme below gives a sequence of reactions starting with a solution of X as the initial reagent: X $\xrightarrow[\text{AgNO}_3(aq)]{\text{HNO}_3(aq)}$ a precipitate $\xrightarrow[\text{dilute } \text{NH}_3(aq)]{\text{excess}}$ a colourless solution $\xrightarrow[\text{HNO}_3(aq)]{\text{excess}}$ a precipitate. Which substance could X be?

Chemical bonding

The percentage of ammonia that could be obtained, if equilibrium was reached in the Haber process, is shown against operating pressure for two temperatures, $400\,^{\circ}\text{C}$ and $500\,^{\circ}\text{C}$. Which diagram shows the two graphs correctly?

Equilibria

The consecutive elements X, Y and Z are located in the third period of the Periodic Table. Element Y has the greatest first ionisation energy and the smallest melting point. What could be the identities of X, Y and Z?

The Periodic Table: chemical periodicity

Which property of Group II elements (beryllium to barium) falls as the atomic number increases?

Group 2

Which element in the third period needs the smallest number of moles of oxygen for the complete combustion of $1\,\text{mol}$ of the element?

The Periodic Table: chemical periodicity

Two characteristics of non-metal elements and the atoms of those elements are given below. Characteristic 1: it forms an oxide that produces a strong acid in water. Characteristic 2: it has no paired $3p$ electrons. Which of these characteristics apply to phosphorus and sulfur?

The Periodic Table: chemical periodicity

The elements radon (Rn), francium (Fr) and radium (Ra) have successive proton numbers in the Periodic Table. In what order do their first ionisation energies occur?

The Periodic Table: chemical periodicity

When gases are moved by road or by rail, they are grouped as: flammable, non-flammable, poisonous. Which gas that is commonly transported is non-flammable?

States of matter

When 2,2-dimethylbutane is heated with chlorine, it undergoes free radical substitution. In one propagation step, the free radical $X\cdot$ is produced. $\text{CH}_3\text{CH}_2\!\!\begin{matrix} \\ | \end{matrix}C\!\!\begin{matrix} \\ | \end{matrix}\text{CH}_3 + \text{Cl}\cdot \rightarrow X\cdot + \text{HCl}$ How many different forms of $X\cdot$ can be formed?

Reaction kinetics

Which reagent would behave differently with the two isomeric alcohols, $(\text{CH}_3)_3\text{CCH}_2\text{OH}$ and $(\text{CH}_3)_2\text{CHCH}_2\text{CH}_2\text{OH}$?

Hydroxy compounds

Which reagent produces similar results with both butanone and butanal?

Carbonyl compounds

When propanone is refluxed with a solution of $\text{NaBH}_4$, what is formed?

Carbonyl compounds

When $\text{CH}_3\text{CO}_2\text{C}_3\text{H}_7$ is hydrolysed by boiling aqueous sodium hydroxide, which compound is produced?

Carboxylic acids and derivatives

In a number of countries, plastic waste is gathered separately and then sorted. A proportion of it is burned to supply heat for power stations. Why is pvc, polyvinylchloride, taken out of any waste before it is burned?

Halogen compounds

When 1,1-dichloroethene undergoes polymerisation, it forms a material with a high density and a high melting point that is impermeable to gases. It is used as cling wrapping. Which arrangement is found in a short section of the polymer chain?

Polymerisation

For an isomer $Y$ with molecular formula $\text{C}_4\text{H}_9\text{Br}$, hydrolysis in aqueous alkali produces the alcohol $\text{C}_4\text{H}_9\text{OH}$. The reaction rate is observed to remain unchanged when the concentration of $\text{OH}^-$ ions present is varied. Which molecular structure is most likely to be $Y$?

Reaction kinetics

Which isomer of $\text{C}_4\text{H}_{10}\text{O}$ produces three alkenes when it is dehydrated?

Hydroxy compounds

Which gas comes nearest to ideal behaviour at room temperature and pressure?

States of matter

Which compound shows both $cis$-$trans$ and optical isomerism?

Chemical bonding

Which diagrams show part of a giant molecular structure?

Chemical bonding

Which of the following reactions are redox reactions?

Electrochemistry

Sodium hydrogensulfide, $\text{NaSH}$, is used to remove hair from animal hides. Which of the following statements about the $\text{SH}^-$ ion are correct?

Chemical bonding

As organic waste rots in water, carboxylic acids are produced. The water turns acidic and aquatic organisms are killed. Which additives are appropriate for removing this acid pollution?

Group 2

Inside a car engine, the non-metal element X produces the pollutant oxide Y. Y undergoes a further oxidation in the atmosphere to form Z. During this additional oxidation, $1\ \text{mol}$ of Y combines with $\frac{1}{2}\ \text{mol}$ of gaseous oxygen. What could X be?

Atoms, molecules and stoichiometry

Sulfur dioxide and sulfites are added as food preservatives. What is the reason for using them in this way?

Electrochemistry

Propanoic acid is found naturally because of bacterial fermentation of milk, and it is partly responsible for the taste of Swiss cheese. Which starting materials could be used to make propanoic acid?

Atoms, molecules and stoichiometry

Which structural formulae correspond to 2,2-dimethylpentane?

Hydrocarbons

Which of these reactions are instances of nucleophilic substitution?

Halogen compounds

The bond energy data below are given. C-H: $410\ \text{kJ mol}^{-1}$ C-Cl: $340\ \text{kJ mol}^{-1}$ Cl-Cl: $244\ \text{kJ mol}^{-1}$ Br-Br: $193\ \text{kJ mol}^{-1}$ These bond energy data correspond to the four reactions shown here. P: $\text{Br}_2 \rightarrow 2\text{Br}$ Q: $2\text{Cl} \rightarrow \text{Cl}_2$ R: $\text{CH}_3 + \text{Cl} \rightarrow \text{CH}_3\text{Cl}$ S: $\text{CH}_4 \rightarrow \text{CH}_3 + \text{H}$ Which sequence correctly arranges the enthalpy changes for these reactions from the most negative to the most positive?

Chemical energetics

The diagram depicts some laboratory apparatus. Which of these preparations could this apparatus be used for?

Organic synthesis

Using the enthalpy changes shown below, $\text{I}_2(g) + 3\text{Cl}_2(g) \rightarrow 2\text{ICl}_3(s) \quad \Delta H^\circ = -214\ \text{kJ mol}^{-1}$ $\text{I}_2(s) \rightarrow \text{I}_2(g) \quad \Delta H^\circ = +38\ \text{kJ mol}^{-1}$ What is the standard enthalpy change of formation of iodine trichloride, $\text{ICl}_3(s)$?

Chemical energetics

When heated, ammonium nitrate, $\text{NH}_4\text{NO}_3$, may break down explosively. $\text{NH}_4\text{NO}_3 \rightarrow \text{N}_2\text{O} + 2\text{H}_2\text{O}$ How do the oxidation numbers of the two nitrogen atoms in $\text{NH}_4\text{NO}_3$ change as this reaction occurs?

Electrochemistry

The Haber process used to produce ammonia is shown by the equation below. $\text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g) \quad \Delta H = -92\ \text{kJ mol}^{-1}$ Which statement is correct for this reaction if the temperature is raised?

Equilibria

A 2.920 g sample of a Group II metal, X, is reacted with excess chlorine to produce 5.287 g of a compound of formula $\text{XCl}_2$. Which metal is X?

Atoms, molecules and stoichiometry

What mass of gas would take up a volume of $3\ \text{dm}^3$ at $25^\circ\text{C}$ and a pressure of 1 atmosphere? [1 mol of gas occupies $24\ \text{dm}^3$ at $25^\circ\text{C}$ under a pressure of 1 atmosphere.]

Atoms, molecules and stoichiometry

Which gas most nearly exhibits ideal behaviour at room temperature and pressure?

States of matter

The Haber process used to produce ammonia is shown by the equation below. $\text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g) \qquad \Delta H = -92\ \text{kJ mol}^{-1}$ Which statement is correct about this reaction if the temperature is raised?

Equilibria

The percentage of ammonia that could be produced if equilibrium was reached in the Haber process is shown against operating pressure for two temperatures, $400^\text{C}$ and $500^\text{C}$. Which diagram shows the two graphs correctly?

Equilibria

Pool water can be kept free from harmful bacteria by adding aqueous sodium chlorate(I), $\text{NaOCl}$. It then reacts with water to form $\text{HOCl}$ molecules, which destroy bacteria. $\text{OCl}^-(aq) + \text{H}_2\text{O} \rightleftharpoons \text{OH}^-(aq) + \text{HOCl}(aq)$ Under strong sunlight, the $\text{OCl}^-$ ion is decomposed by ultra-violet light. $\text{OCl}^-(aq) + \text{uv light} \rightarrow \text{Cl}^-(aq) + \tfrac{1}{2}\text{O}_2(g)$ Which method would keep the concentration of $\text{HOCl}(aq)$ at the highest level?

Equilibria

$\text{Na}_2\text{S}_2\text{O}_3$ reacts with dilute $\text{HCl}$ and produces a pale yellow precipitate. When $1\ \text{cm}^3$ of $0.1\ \text{mol dm}^{-3}\ \text{HCl}$ is added to $10\ \text{cm}^3$ of $0.02\ \text{mol dm}^{-3}\ \text{Na}_2\text{S}_2\text{O}_3$, the precipitate appears slowly. If the test is done again using $1\ \text{cm}^3$ of $0.1\ \text{mol dm}^{-3}\ \text{HCl}$ and $10\ \text{cm}^3$ of $0.05\ \text{mol dm}^{-3}\ \text{Na}_2\text{S}_2\text{O}_3$, the precipitate appears more rapidly. What accounts for this?

Reaction kinetics

What happens when concentrated sulfuric acid reacts with sodium chloride?

Group 17

$X$ is a salt of one of the halogens chlorine, bromine, iodine or astatine (proton number $85$). The reaction scheme illustrates a sequence of reactions that begins with a solution of $X$ as the starting reagent. $X \xrightarrow[\text{AgNO}_3(aq)]{\text{HNO}_3(aq)} \text{a precipitate} \xrightarrow[\text{excess}]{\text{dilute } \text{NH}_3(aq)} \text{a colourless solution} \xrightarrow[\text{excess}]{\text{HNO}_3(aq)} \text{a precipitate}$ What could $X$ be?

Chemical bonding

Which element in the third period needs the smallest number of moles of oxygen for the complete combustion of $1$ mol of that element?

Atoms, molecules and stoichiometry

Two characteristics of non-metal elements and their atoms are given below. property $1$ forms an oxide that can make a strong acid in water property $2$ does not have paired $3p$ electrons Which of these properties are shown by phosphorus and sulfur?

The Periodic Table: chemical periodicity

Three neighbouring elements $X$, $Y$ and $Z$ are located in the third period of the Periodic Table. Element $Y$ has the greatest first ionisation energy and the lowest melting point. What might the identities of $X$, $Y$ and $Z$ be?

The Periodic Table: chemical periodicity

Which property of Group II elements (beryllium to barium) becomes smaller as atomic number increases?

Group 2

The Data Booklet may be needed for this question. What might the proton number be of an element whose atoms each contain three unpaired electrons?

Atomic structure

When gaseous chemicals are moved by road or by rail, they are put into the following categories. flammable  non-flammable  poisonous Which gas that is commonly transported is non-flammable?

States of matter

Which reagent will react in different ways with the two isomeric alcohols, $(\text{CH}_3)_3\text{CCH}_2\text{OH}$ and $(\text{CH}_3)_2\text{CHCH}_2\text{CH}_2\text{OH}$?

Hydroxy compounds

Which reagent would produce comparable results for both butanone and butanal?

Carbonyl compounds

What product is produced when propanone is refluxed with a solution of $\text{NaBH}_4$?

Carbonyl compounds

Which compound is produced when $\text{CH}_3\text{CO}_2\text{C}_3\text{H}_7$ is hydrolysed by boiling aqueous sodium hydroxide?

Carboxylic acids and derivatives

On heating with chlorine, the hydrocarbon 2,2-dimethylbutane reacts by free radical substitution. In a propagation step, the free radical X• is generated: $\text{(structure)} + \text{Cl}• \rightarrow X• + \text{HCl}$ How many distinct forms of X• can be produced?

Hydrocarbons

When an isomer Y with molecular formula $\text{C}_4\text{H}_9\text{Br}$ is hydrolysed in aqueous alkali to give an alcohol $\text{C}_4\text{H}_9\text{OH}$, the reaction rate is observed to remain unchanged when the concentration of $\text{OH}^-$ ions present is altered. Which molecular structure of Y is the most likely?

Reaction kinetics

Which isomer of $\text{C}_4\text{H}_{10}\text{O}$ produces three alkenes when it is dehydrated?

Hydroxy compounds

Which compound has both cis-trans and optical isomerism?

Chemical bonding

In many nations, plastic waste is gathered separately and sorted. A portion of this is burned to generate heat for power stations. Why is pvc, polyvinylchloride, taken out of any waste that is to be incinerated?

Halogen compounds

Consulting the Data Booklet is useful for answering this question. In the Periodic Table, the elements radon (Rn), francium (Fr) and radium (Ra) are arranged in successive proton numbers. In which order do their first ionisation energies occur?

The Periodic Table: chemical periodicity

Polymerisation of 1,1-dichloroethene gives a compact substance with a high melting point that does not let gases pass through. It is used for cling wrapping. Which repeating sequence is found in a short section of the polymer chain?

Polymerisation

Sodium hydrogensulfide, $\text{NaSH}$, is used to remove hair from animal hides. Which of the following statements about the $\text{SH}^-$ ion are correct?

Chemical bonding

Which diagrams show part of a giant molecular structure?

Chemical bonding

Which of these reactions count as redox reactions?

Electrochemistry

As organic waste decays in water, carboxylic acids are produced. The water then turns acidic and aquatic organisms are killed. Which additives are appropriate for removing this acid pollution?

Equilibria

Within a car engine, the non-metal element X produces the pollutant oxide Y. Y then undergoes further oxidation to Z in the atmosphere. During this extra oxidation, $1$ mol of Y reacts with $\frac{1}{2}$ mol of gaseous oxygen. Which element could X be?

Nitrogen and sulfur

Sulfur dioxide and sulfites are added to food to help with preservation. Why are they suitable for this use?

Nitrogen and sulfur

Which of these reactions are instances of nucleophilic substitution?

Halogen compounds

Propanoic acid is present naturally as a product of bacterial fermentation of milk, and it contributes in part to the flavour of Swiss cheese. Which starting materials could be used to synthesise propanoic acid?

Carboxylic acids and derivatives

Which structural formulae correspond to 2,2-dimethylpentane?

Atoms, molecules and stoichiometry

The bond energy data shown are listed here. Bond energies: C-H: $410\ \text{kJ mol}^{-1}$ C-Cl: $340\ \text{kJ mol}^{-1}$ Cl-Cl: $244\ \text{kJ mol}^{-1}$ Br-Br: $193\ \text{kJ mol}^{-1}$ These bond energy values correspond to the four reactions below: P: $\text{Br}_2 \rightarrow 2\text{Br}$ Q: $2\text{Cl} \rightarrow \text{Cl}_2$ R: $\text{CH}_3 + \text{Cl} \rightarrow \text{CH}_3\text{Cl}$ S: $\text{CH}_4 \rightarrow \text{CH}_3 + \text{H}$ In which sequence do the enthalpy changes of these reactions run from the most negative to the most positive?

Chemical energetics

The diagram illustrates some laboratory apparatus. Which preparations can be carried out using this apparatus?

Analytical techniques

Using the enthalpy changes shown below, $I_2(g) + 3\text{Cl}_2(g) \rightarrow 2\text{ICl}_3(s)$ $\Delta H^\circ = -214\ \text{kJ mol}^{-1}$ $I_2(s) \rightarrow I_2(g)$ $\Delta H^\circ = +38\ \text{kJ mol}^{-1}$ Calculate the standard enthalpy change of formation for iodine trichloride, $\text{ICl}_3(s)$?

Chemical energetics

Ammonium nitrate, $\text{NH}_4\text{NO}_3$, may break down explosively if heated. $\text{NH}_4\text{NO}_3 \rightarrow \text{N}_2\text{O} + 2\text{H}_2\text{O}$ How do the oxidation numbers of the two nitrogen atoms in $\text{NH}_4\text{NO}_3$ change as this reaction occurs?

Electrochemistry

What mass of gas would fill a volume of $3\ \text{dm}^3$ at $25^\circ\text{C}$ and $1$ atmosphere pressure? [At $25^\circ\text{C}$ and $1$ atmosphere pressure, $1$ mol of gas occupies $24\ \text{dm}^3$.]

Atoms, molecules and stoichiometry

The Data Booklet may be needed for this question. $2.920\ \text{g}$ of a Group II metal, $X$, is reacted with an excess of chlorine, producing $5.287\ \text{g}$ of a compound with formula $X\text{Cl}_2$. What is the identity of metal $X$?

Atoms, molecules and stoichiometry

The table shows the concentrations and $\text{pH}$ readings for the aqueous solutions of two compounds, $X$ and $Y$. Each compound may be either an acid or a base. For $X$: concentration $= 2\ \text{mol dm}^{-3}$, $\text{pH} = 6$ For $Y$: concentration $= 2\ \text{mol dm}^{-3}$, $\text{pH} = 9$ Student P decided that $X$ is a strong acid. Student Q decided that the degree of dissociation is smaller in $X(aq)$ than in $Y(aq)$. Which student(s) are correct?

Equilibria

At room temperature and pressure, which gas is nearest to ideal behaviour?

States of matter

The table shows the concentrations and pH values for the aqueous solutions of two compounds, $X$ and $Y$. Each compound may be either an acid or a base. Student P decided that $X$ is a strong acid. Student Q decided that the degree of dissociation is smaller in $X(aq)$ than in $Y(aq)$. Which students are right?

Equilibria

What is the behaviour of concentrated sulfuric acid when it reacts with sodium chloride?

Atoms, molecules and stoichiometry

Swimming pool water can be made free from harmful bacteria by adding aqueous sodium chlorate(I), $\text{NaOCl}$. In water, this forms $\text{HOCl}$ molecules, and these kill bacteria. $\text{OCl}^-\text{(aq)} + \text{H}_2\text{O} \rightleftharpoons \text{OH}^-\text{(aq)} + \text{HOCl}\text{(aq)}$ Under bright sunshine, the $\text{OCl}^-$ ion is decomposed by ultra-violet light. $\text{OCl}^-\text{(aq)} + \text{uv light} \rightarrow \text{Cl}^-\text{(aq)} + \tfrac{1}{2}\text{O}_2\text{(g)}$ Which approach would keep the concentration of $\text{HOCl}\text{(aq)}$ at the highest level?

Equilibria

$\text{Na}_2\text{S}_2\text{O}_3$ reacts with dilute $\text{HCl}$ to form a pale yellow precipitate. When $1\,\text{cm}^3$ of $0.1\,\text{mol dm}^{-3}$ $\text{HCl}$ is mixed with $10\,\text{cm}^3$ of $0.02\,\text{mol dm}^{-3}$ $\text{Na}_2\text{S}_2\text{O}_3$, the precipitate appears slowly. When the experiment is carried out again using $1\,\text{cm}^3$ of $0.1\,\text{mol dm}^{-3}$ $\text{HCl}$ and $10\,\text{cm}^3$ of $0.05\,\text{mol dm}^{-3}$ $\text{Na}_2\text{S}_2\text{O}_3$, the precipitate appears more rapidly. Why does this happen?

Reaction kinetics

X is a salt of a halogen such as chlorine, bromine, iodine, or astatine (proton number 85). The reaction scheme below shows a sequence of reactions, with a solution of X used as the initial reagent. $X \xrightarrow[\text{AgNO}_3\text{(aq)}]{\text{HNO}_3\text{(aq)}}$ a precipitate $\xrightarrow{\text{an excess of dilute NH}_3\text{(aq)}}$ a colourless solution $\xrightarrow{\text{an excess of HNO}_3\text{(aq)}}$ a precipitate What might X be?

Group 17

The proportion of ammonia that could be obtained, provided equilibrium was reached in the Haber process, is shown as a function of operating pressure for two temperatures, $400\,^\circ\text{C}$ and $500\,^\circ\text{C}$. Which diagram is the correct representation of the two graphs?

Equilibria

The following are two characteristics of non-metallic elements and the atoms of those elements. property 1: forms an oxide that produces a strong acid when dissolved in water property 2: does not have paired $3p$ electrons Which of these properties are found in phosphorus and sulfur?

The Periodic Table: chemical periodicity

Three successive elements X, Y and Z are located in the third period of the Periodic Table. Element Y has the greatest first ionisation energy and the smallest melting point. What could be the identities of X, Y and Z?

The Periodic Table: chemical periodicity

Which characteristic of Group II elements (beryllium to barium) gets smaller as atomic number increases?

Group 2

Which third-period element needs the fewest moles of oxygen for the complete combustion of $1\,\text{mol}$ of the element?

Atoms, molecules and stoichiometry

The Data Booklet may be used for this question. The elements radon (Rn), francium (Fr) and radium (Ra) have consecutive proton numbers in the Periodic Table. In what order do their first ionisation energies increase?

The Periodic Table: chemical periodicity

When gaseous chemicals are moved by road or by rail, they are grouped as shown below. flammable non-flammable poisonous Which gas that is commonly transported is non-flammable?

States of matter

Which substance would react differently with the two isomeric alcohols, $(\text{CH}_3)_3\text{CCH}_2\text{OH}$ and $(\text{CH}_3)_2\text{CHCH}_2\text{CH}_2\text{OH}$?

Chemical bonding

Which product is produced when propanone is refluxed with a solution of $\text{NaBH}_4$?

Carbonyl compounds

On heating with chlorine, the hydrocarbon $2,2$-dimethylbutane undergoes free radical substitution. During a propagation stage, the free radical $X^\bullet$ is produced. $\text{CH}_3\text{CH}_2\!\!\begin{array}{c}\text{C}\\|\\\text{CH}_3\end{array}\!\!\text{CH}_3\; + \text{Cl}^\bullet \rightarrow X^\bullet + \text{HCl}$ How many different forms of $X^\bullet$ can be formed?

Reaction kinetics

Which reagent would produce similar outcomes with both butanone and butanal?

Carbonyl compounds

Which compound is produced when $\text{CH}_3\text{CO}_2\text{C}_3\text{H}_7$ is hydrolysed by heating with aqueous sodium hydroxide?

Carboxylic acids and derivatives

Which compound displays both cis-trans and optical isomerism?

An introduction to AS Level organic chemistry

In a number of countries, plastic waste is gathered separately and then sorted. Part of it is burnt to generate heat for power stations. Why is PVC, polyvinylchloride, taken out of any waste that will be incinerated?

Halogen compounds

When 1,1-dichloroethene undergoes polymerisation, it forms a dense substance with a high melting point that gases cannot diffuse through. It is used as cling wrapping. Which sequence is shown in a short section of the polymer chain?

Chemical bonding

When an isomer Y with molecular formula $\text{C}_4\text{H}_9\text{Br}$ is hydrolysed in aqueous alkali to give an alcohol $\text{C}_4\text{H}_9\text{OH}$, the reaction rate is observed to remain unchanged when the concentration of $\text{OH}^-$ ions present is altered. Which molecular structure is most likely to be Y?

Reaction kinetics

For this question, the Data Booklet may be useful. What could the proton number be for an element whose atoms each have three unpaired electrons?

Atomic structure

Which isomer of $\text{C}_4\text{H}_{10}\text{O}$ produces three alkenes when it is dehydrated?

Hydroxy compounds

Which of the following reactions are redox reactions?

Electrochemistry

Sodium hydrogensulfide, $\text{NaSH}$, is employed to strip hair from animal hides. Which of the following statements about the $\text{SH}^-$ ion are correct?

Chemical bonding

Which diagrams show part of a giant molecular structure?

Chemical bonding

Within an automobile engine, a non-metal element X produces pollutant oxide Y. In the atmosphere, Y then undergoes further oxidation to form Z. For this additional oxidation, $1$ mol of Y reacts with $\frac{1}{2}$ mol of gaseous oxygen. Which element could X be?

Atoms, molecules and stoichiometry

As organic refuse decays in water, carboxylic acids are produced. The water becomes acidic and aquatic life is destroyed. Which additives are suitable for removing this acid pollution?

Equilibria

Sulfur dioxide and sulfites are used in food preservation. What is the reason for using them for this purpose?

Electrochemistry

Which structural formulae show 2,2-dimethylpentane?

Atoms, molecules and stoichiometry

Which of the following reactions are examples of nucleophilic substitution?

Chemical bonding

Propanoic acid is formed naturally during the bacterial fermentation of milk, and it contributes partly to the flavour of Swiss cheese. Which starting materials could be used to synthesise propanoic acid?

Carboxylic acids and derivatives

Using the enthalpy changes below, $\text{I}_2(g) + 3\text{Cl}_2(g) \rightarrow 2\text{ICl}_3(s)$, $\Delta H^\circ = -214\,\text{kJ mol}^{-1}$ $\text{I}_2(s) \rightarrow \text{I}_2(g)$, $\Delta H^\circ = +38\,\text{kJ mol}^{-1}$ What is the standard enthalpy change of formation of iodine trichloride, $\text{ICl}_3(s)$?

Chemical energetics

The diagram shows some laboratory apparatus. For which preparations could this apparatus be used?

Analytical techniques

Several bond energy values are given below. These bond energy values are connected to the following four reactions: $\text{P: } \text{Br}_2 \rightarrow 2\text{Br}$ $\text{Q: } 2\text{Cl} \rightarrow \text{Cl}_2$ $\text{R: } \text{CH}_3 + \text{Cl} \rightarrow \text{CH}_3\text{Cl}$ $\text{S: } \text{CH}_4 \rightarrow \text{CH}_3 + \text{H}$ In what sequence should the enthalpy changes for these reactions be arranged, from the most negative to the most positive?

Chemical energetics

What mass of gas would fill a volume of $3\,\text{dm}^3$ at $25^\circ\text{C}$ and $1$ atmosphere pressure? [$1\,\text{mol}$ of gas occupies $24\,\text{dm}^3$ at $25^\circ\text{C}$ and $1$ atmosphere pressure.]

Atoms, molecules and stoichiometry

Ammonium nitrate, $\text{NH}_4\text{NO}_3$, may undergo explosive decomposition on heating. $\text{NH}_4\text{NO}_3 \rightarrow \text{N}_2\text{O} + 2\text{H}_2\text{O}$ How do the oxidation numbers of the two nitrogen atoms in $\text{NH}_4\text{NO}_3$ change as this reaction occurs?

Electrochemistry

The Haber process used to produce ammonia is shown by the equation below. $\text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g)$\quad $\Delta H = -92\,\text{kJ mol}^{-1}$ Which statement is true for this reaction if the temperature is raised?

Equilibria

The Data Booklet is needed for this question. $2.920\,\text{g}$ of a Group II metal, $X$, reacts with excess chlorine to produce $5.287\,\text{g}$ of a compound with formula $\text{XCl}_2$. What is the identity of metal $X$?

Atoms, molecules and stoichiometry