May/June 2013

Solutions that contain chlorate(I) ions are used as household bleach agents and disinfectants. On heating, these solutions decompose as shown. $3\text{ClO}^- \rightarrow \text{ClO}_3^- + 2\text{Cl}^-$ What oxidation state does chlorine have in each of these three ions?

Electrochemistry

The general gas equation may be applied to determine the $M_r$ of a gas. For a gas sample with mass $m\ \text{g}$, which expression gives the value of $M_r$?

States of matter

A solution containing $ ext{Sn}^{2+}$ ions can reduce an acidified solution of $ ext{MnO}_4^-$ ions to form $ ext{Mn}^{2+}$ ions. In this process, the $ ext{Sn}^{2+}$ ions are oxidised into $ ext{Sn}^{4+}$ ions. How many moles of $ ext{Mn}^{2+}$ ions are produced when a solution made from $9.5\,\text{g}$ of $ ext{SnCl}_2$ ($M_r = 190$) is added to excess acidified $ ext{KMnO}_4$ solution?

Electrochemistry

Bond enthalpy data should be used to answer this question. The equation below shows the complete combustion of methane. $\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O}$ What is the enthalpy change of combustion of methane?

Chemical energetics

In which table row are every one of the statements that compare the compounds of magnesium and barium correct?

Group 2

What occurs when iodine solution is added to a sodium bromide solution?

Electrochemistry

Element $85$, astatine, belongs to Group VII. Concentrated sulfuric acid is added to sodium astatide. A mixture of products is formed, containing astatine, hydrogen astatide, hydrogen sulfide, and sodium sulfate. Which product is produced by the oxidation of one of the ions in sodium astatide?

Electrochemistry

Magnesium nitrate, $\text{Mg(NO}_3\text{)}_2$, decomposes on heating to form a white solid together with a mixture of gases. One gas given off is a nitrogen oxide, $X$. $7.4\,\text{g}$ of anhydrous magnesium nitrate is heated until the reaction is complete. What mass of $X$ is produced?

Atoms, molecules and stoichiometry

$Y$ is a salt of one of the halogens chlorine, bromine, iodine, or astatine (element $85$). The reaction scheme illustrates a sequence of reactions in which a solution of $Y$ is used as the starting reagent.

Group 17

Sulfur trioxide is made from sulfur dioxide and oxygen by means of the Contact process. Which condition changes the value of the equilibrium constant, $K_c$?

Equilibria

Which reagent, if heated together with ammonium sulfate, gives off ammonia?

Nitrogen and sulfur

A blend of $10\ \text{cm}^3$ of methane and $10\ \text{cm}^3$ of ethane was ignited with an excess of oxygen. Once it had cooled to room temperature, the remaining gas was then led through aqueous potassium hydroxide. Every gas volume was measured at the same temperature and pressure. What volume of gas did the alkali absorb?

Atoms, molecules and stoichiometry

The compounds below are present in the seaweed $\textit{Asparagopsis taxiformis}$. Which compound could exhibit both $cis$-$trans$ isomerism and optical isomerism?

Chemical bonding

Lactic acid ($2$-hydroxypropanoic acid), $\text{CH}_3\text{CH(OH)CO}_2\text{H}$, is present in sour milk. Which reaction might lactic acid undergo?

Carboxylic acids and derivatives

Bromine reacts with ethene to produce $1,2$-dibromoethane. Which option gives the correct description of the organic intermediate in this reaction?

Hydrocarbons

Chloroethane may be converted into sodium propanoate. $\text{chloroethane} \rightarrow Q \rightarrow \text{sodium propanoate}$ To form sodium propanoate, the intermediate, $Q$, is hydrolysed using boiling aqueous sodium hydroxide. Which reagent would convert chloroethane into the intermediate, $Q$?

Chemical bonding

Aqueous sodium hydroxide reacts with $1$-bromopropane to form propan-$1$-ol. What is the correct description of the first step in the mechanism?

Halogen compounds

Pentane, $\text{C}_5\text{H}_{12}$, is reacted with chlorine under ultraviolet light. One of the products is compound $R$. $R$ has molecular formula $\text{C}_5\text{H}_{10}\text{Cl}_2$. Every molecule of $R$ contains one chiral carbon atom. In this isomer, which two atoms of the pentane chain could each be attached to chlorine atoms?

Chemical bonding

The Data Booklet may be useful for this question. $2.30\,\text{g}$ of ethanol was combined with an excess of aqueous acidified potassium dichromate(VI). The reaction mixture was then heated under reflux for one hour. The required organic product was then obtained by distillation. The percentage yield of product was $60.0\%$. What mass of product was collected?

Atoms, molecules and stoichiometry

One substance contributing to the distinctive smell of burnt sugar is the compound below: $\text{CH}_3\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\rightarrow$ (the structure shows $\text{CH}_3\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\rightarrow$ $\text{CH}_3\text{COCHO}$) This compound has two functional groups. Which reagent reacts with only one of the functional groups?

Chemical bonding

Below is the structural formula for compound $X$: $\text{CH}_3\text{CH}_2\text{CH}_2\text{OCHO}$ What is compound $X$ called, and how does its boiling point compare with the boiling point of butanoic acid?

Chemical bonding

Synthetic resins, plasticisers and many other chemicals may be produced through polymerisation of a range of monomers, including prop-2-en-1-ol, $\text{CH}_2{=}\text{CHCH}_2\text{OH}$. Which structure shows the repeat unit in poly(prop-2-en-1-ol)?

Polymerisation

The diagram illustrates an electrolytic cell used to extract aluminium. Which statement is correct?

Electrochemistry

Certain vegetable oils contain ‘trans fats’, which are linked to unwanted rises in blood cholesterol levels. In the diagrams below, $R_1$ and $R_2$ are two different hydrocarbon chains. Which diagram shows an optically active ‘trans fat’ correctly?

Chemical bonding

Referring to the Data Booklet will be helpful for this question. Free-radicals have a significant role in reactions that lead to the destruction of the ozone layer and in the substitution of alkanes by chlorine. Certain free-radicals have two unpaired electrons. These species are known as diradicals. Which species are diradicals?

Chemical bonding

Compared with the Group I metals, the Group II metals have higher melting points. Which factors might help to explain the higher melting points?

Chemical bonding

When answering this question, apply valence shell electron pair repulsion theory. Which species have trigonal planar geometry?

Chemical bonding

The graph shows the first ionisation energies of twenty consecutive elements in the Periodic Table. The letters shown are not the usual symbols for these elements. Which of the following statements about the graph are correct?

The Periodic Table: chemical periodicity

Solids W, X, Y and Z are compounds of two different Group II metals. Their uses are outlined below. Compound W is used as a refractory lining material in kilns. Compound X is used as a building material. It may also be heated in a kiln to produce compound Y. When Y is hydrated, it produces compound Z, which is used in agriculture to treat soils. Which statements about these compounds are correct?

Group 2

When a red-hot platinum wire is lowered into a test tube containing hydrogen iodide, the gas breaks down into its elements. If the same experiment is carried out with hydrogen chloride, there is no reaction. Which factors help explain this behaviour?

Group 17

In the mixture formed during the photochemical chlorination of methane, which molecules would be found?

Halogen compounds

In which reactions does the reagent oxidise the organic compound?

Electrochemistry

A sun protection cream includes the ester shown below as its active ingredient. Which substances are found among the products formed when it is hydrolysed by aqueous sodium hydroxide?

Carboxylic acids and derivatives

The elements radon (Rn), francium (Fr) and radium (Ra) have proton numbers 86, 87 and 88 respectively. How do their first ionisation energies rank in order?

The Periodic Table: chemical periodicity

Which of the following reagents, if used in excess, can be used to convert lactic acid, $\text{CH}_3\text{CH}(\text{OH})\text{CO}_2\text{H}$, into sodium lactate, $\text{CH}_3\text{CH}(\text{OH})\text{CO}_2\text{Na}$?

Atoms, molecules and stoichiometry

For which species do the numbers of protons, neutrons and electrons all differ?

Atomic structure

An experiment is arranged to determine the rate of hydrolysis of ethyl ethanoate. $\text{CH}_3\text{CO}_2\text{C}_2\text{H}_5 + \text{H}_2\text{O} \rightleftharpoons \text{CH}_3\text{CO}_2\text{H} + \text{C}_2\text{H}_5\text{OH}$ It is observed that the hydrolysis is slow in neutral aqueous solution, but it takes place at a measurable rate when the solution is acidified with hydrochloric acid. What does the hydrochloric acid do?

Reaction kinetics

The reaction pathway for a reversible reaction is displayed below. Which statement is right?

Chemical energetics

What causes the rate of a gaseous reaction to rise when the pressure is increased at a constant temperature?

Reaction kinetics

Which substance would show the least ideal-gas behaviour at room temperature?

States of matter

In the electrolysis of molten aluminium oxide for the production of aluminium with carbon electrodes, two reactions take place one after the other at the anode, and each one gives a different gas. What happens to the oxidation number of oxygen in these reactions?

Electrochemistry

This question requires use of the Data Booklet. A student combined $25\ \text{cm}^3$ of $0.10\ \text{mol dm}^{-3}$ sodium hydroxide solution with $25\ \text{cm}^3$ of $0.10\ \text{mol dm}^{-3}$ hydrochloric acid and observed a temperature increase of $2.5^\circ\text{C}$. Determine the enthalpy change for the reaction per mole of NaOH.

Chemical energetics

What energy change is represented by the enthalpy change of atomisation of hydrogen at $298\ \text{K}$?

Chemical energetics

Propanone has the molecular formula $\text{C}_3\text{H}_6\text{O}$. The enthalpy change of combustion of hydrogen is $-286\ \text{kJ mol}^{-1}$. The enthalpy change of combustion of carbon is $-394\ \text{kJ mol}^{-1}$. The enthalpy change of formation of propanone is $-254\ \text{kJ mol}^{-1}$. Using this data, what is the enthalpy change of combustion of propanone?

Chemical energetics

Information from the Data Booklet may be needed for this question. When magnesium nitrate, $\text{Mg(NO}_3)_2$, is heated, it decomposes to form a white solid and a mixture of gases; oxygen is one of the gases given off. A sample of $29.7\ \text{g}$ of anhydrous magnesium nitrate is heated until the reaction is complete. What mass of oxygen is formed?

Atoms, molecules and stoichiometry

Which row in the table contains only statements that correctly compare the compounds of calcium and barium?

Group 2

Halogen lamps are fitted to many modern cars. Right after these lamps are switched on, a noticeable purple colour can be observed. Which species is causing this purple colour?

Group 17

The graphs show the patterns for three physical properties of the elements Na, Mg, Al, Si, P and S. Which physical property is not shown?

The Periodic Table: chemical periodicity

Which statement about ammonia is fully correct?

Nitrogen and sulfur

What occurs when bromine solution is added to a solution of sodium iodide?

Electrochemistry

Halogens are present as diatomic molecules, $\text{X}_2$. The boiling points of the Group VII elements rise down the group from chlorine to iodine. Which statement best explains why the boiling point increases as Group VII is descended?

States of matter

Four equations for enthalpy changes are given below. $\text{Na(g)} \rightarrow \text{Na}^+(g) + e^- \quad \Delta H = W$ $\text{Na(g)} \rightarrow \text{Na}^{2+}(g) + 2e^- \quad \Delta H = X$ $\text{Na(s)} \rightarrow \text{Na(g)} \quad \Delta H = Y$ $\text{Na(s)} \rightarrow \text{Na}^{2+}(g) + 2e^- \quad \Delta H = Z$ Determine the second ionisation energy of sodium.

Chemical energetics

The compound hex-3-en-1-ol, P, has a strong 'leafy' scent like freshly cut grass and is used in perfumery. $\text{CH}_3\text{CH}_2\text{CH}=\text{CHCH}_2\text{CH}_2\text{OH}$. What is formed when P is treated with excess hot concentrated acidified $\text{KMnO}_4$?

Hydrocarbons

Sorbic acid is used as a food preservative because it destroys fungi and moulds. In the presence of a nickel catalyst, sorbic acid reacts with hydrogen, and it also reacts with bromine in an organic solvent. How many moles of hydrogen and of bromine are added to one mole of sorbic acid in these reactions?

Atoms, molecules and stoichiometry

On heating with chlorine, the hydrocarbon $2,2$-dimethylbutane undergoes free radical substitution. During a propagation step, a free radical $X\bullet$ is produced: $\text{CH}_3\text{CH}_2\text{C(CH}_3)_2\text{CH}_3 + \text{Cl}\bullet \rightarrow X\bullet + \text{HCl}$. How many different forms of $X\bullet$ can exist?

Reaction kinetics

When 2-bromo-2-methylpropane is treated with aqueous sodium hydroxide, 2-methylpropan-2-ol is formed. The reaction follows an $S_N1$ mechanism. How should the initial step in the mechanism be described?

Reaction kinetics

Compound $Y$ may be hydrolysed using warm aqueous silver nitrate, producing a precipitate that dissolves in dilute aqueous ammonia. Compound $Y$ is also able to take part in an elimination reaction to give an alkene. What might be the skeletal formula of compound $Y$?

Halogen compounds

The molecule shown is menthol, an alcohol that occurs naturally in peppermint oil. If menthol is heated with concentrated sulfuric acid, a reaction takes place. One of the substances formed is compound $T$. What might the structure of compound $T$ be?

Chemical bonding

What volume of oxygen, measured at room temperature and pressure, is required for complete combustion of $0.1$ mol of propan-1-ol?

Atoms, molecules and stoichiometry

Which carbonyl compound reacts with hydrogen cyanide to produce a product that contains no chiral carbon atom?

Carbonyl compounds

How many of the compounds listed below give a carboxylic acid when heated under reflux with hot acidified $\text{K}_2\text{Cr}_2\text{O}_7$? $\text{CH}_3\text{CH}_2\text{CHO}$ $\text{CH}_3\text{COCH}_3$ $\text{CH}_3\text{CH}_2\text{CH}_2\text{OH}$ $\text{CH}_3\text{CHOHCH}_3$

Electrochemistry

The compound $Y$ has an $M_r$ of $88$. When it is added to a solution of sodium hydrogencarbonate, no fizzing occurs. It can be hydrolysed by dilute sulfuric acid to give two organic products with $M_r$ values of $46$ and $60$. What is the identity of compound $Y$?

Carboxylic acids and derivatives

Which ion contains more electrons than protons, and more protons than neutrons? [$\text{H} = ^{1}_{1}\text{H};\ \text{D} = ^{2}_{1}\text{H};\ \text{O} = ^{16}_{8}\text{O}$]

Atomic structure

When ethene undergoes polymerisation, poly(ethene) is produced. How does the carbon-carbon bond in poly(ethene) differ from the bond in ethene?

Polymerisation

Which of the pairs below contains two species with the same count of unpaired $p$ electrons?

Atomic structure

The diagram illustrates the reaction pathway of a reversible reaction. Which statements are correct?

Chemical energetics

Which substances have delocalised electrons present?

Chemical bonding

Solids $W$, $X$, $Y$ and $Z$ are compounds made from two different Group II metals. Their uses are outlined below. Compound $W$ serves as a refractory lining material in kilns. Compound $X$ is used as a construction material. It may also be heated in a kiln to produce compound $Y$. When $Y$ is hydrated, compound $Z$ is formed; this is used in agriculture to treat soils. Which statements about these compounds are correct?

Group 2

Which of these properties increases along the sequence hydrogen chloride, hydrogen bromide and hydrogen iodide?

Chemical bonding

Sulfur dioxide is an atmospheric pollutant responsible for acid rain. One reaction in this sequence is the conversion of sulfur dioxide into sulfur trioxide by oxidation. This oxidation occurs in a two-stage reaction that involves oxygen and nitrogen monoxide, NO. $\text{NO} + \frac{1}{2}\text{O}_2 \rightarrow \text{NO}_2$ $\text{NO}_2 + \text{SO}_2 \rightarrow \text{SO}_3 + \text{NO}$ Which of the following statements are correct?

Reaction kinetics

What properties do fluoroalkanes have?

Halogen compounds

Which substance is formed when an aqueous solution of butan-2-ol undergoes oxidation under suitable conditions?

Electrochemistry

Compound X has an $M_r$ of 72. Its percentage composition by mass is 66.7% carbon, 11.1% hydrogen and 22.2% oxygen. X produces an orange precipitate with 2,4-dinitrophenylhydrazine reagent. X shows no reaction with Fehling’s reagent. What may be concluded from these data?

Carbonyl compounds

What factor can influence the value of the activation energy of a reaction?

Reaction kinetics

An organic compound, Z, reacts with calcium metal and forms a salt with the empirical formula $\text{CaC}_4\text{H}_6\text{O}_4$. Which compound could Z be?

Atoms, molecules and stoichiometry

The diagram illustrates the Maxwell-Boltzmann energy distribution curves for molecules in a gas sample at two temperatures. On the axes, which letter indicates the most probable energy for the molecules at the lower temperature?

States of matter

In the solid state, which pair of elements has the same type of chemical bond between its atoms?

Chemical bonding

Ethanol has a boiling point of $78^\circ\text{C}$. When the pressure is $101\ \text{kPa}$ and the temperature is $79^\circ\text{C}$, ethanol vapour does not obey the gas equation $pV = nRT$ exactly. What is the reason for this?

States of matter

The reaction involving sulfur dioxide and oxygen is a dynamic equilibrium. $2\text{SO}_2(g) + \text{O}_2(g) \rightleftharpoons 2\text{SO}_3(g)$ What occurs when the pressure of the system is increased?

Equilibria

Dicarbon monoxide, $\text{C}_2\text{O}$, occurs in dust clouds in space. Study of this substance shows that the atoms in this molecule are arranged as $\text{C}-\text{C}-\text{O}$. Every bond is a double bond and there are no unpaired electrons. How many lone pairs of electrons are in a molecule of $\text{C}_2\text{O}$?

Chemical bonding

For the redox equation below, what happens to the oxidation states of vanadium and sulfur? $\text{VO}_2^{+} + \text{SO}_2 \rightarrow \text{V}^{3+} + \text{SO}_4^{2-}$

Electrochemistry

This question requires consultation of the Data Booklet. One of the substances in a washing powder is sodium hydrogencarbonate, $\text{NaHCO}_3$. During a titration, a sample containing $1.00\,\text{g}$ of washing powder needs $7.15\,\text{cm}^3$ of $0.100\,\text{mol dm}^{-3}$ sulfuric acid to react completely. Only the sodium hydrogencarbonate present in the washing powder reacts with the acid. Determine the percentage by mass of sodium hydrogencarbonate in the washing powder.

Atoms, molecules and stoichiometry

This question requires use of the Data Booklet. Answer this question using bond enthalpy data. The equation below shows the complete combustion of methanal. $ \text{H}_2\text{C}=\text{O} + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O} $ What is the enthalpy change of combustion for methanal?

Chemical energetics

The Data Booklet is required for this question. When heated, anhydrous magnesium nitrate, $\text{Mg(NO}_3)_2$, decomposes to form a white solid and a mixture of two gases X and Y. Y is oxygen. What is the ratio $\dfrac{\text{mass of X formed}}{\text{mass of Y formed}}$?

Atoms, molecules and stoichiometry

In which table row are all the comparisons between magnesium and barium correct?

Group 2

Two students, P and Q, were told to produce bar charts showing the differences in size of some properties of the halogens and their compounds. Their diagrams are shown. Which of the students’ diagrams is/are correct?

Group 17

When iodine is heated, a vapour forms. Which row in the table correctly states the species present in the vapour and its colour?

States of matter

How do the strengths of the covalent bonds inside the molecules, and the van der Waals’ forces between molecules, alter as you move down Group VII from chlorine to bromine to iodine?

Chemical bonding

Graphs may be plotted to illustrate the percentage of ammonia present at equilibrium when nitrogen and hydrogen are combined at various temperatures and pressures. Which diagram shows these two graphs correctly?

Equilibria

In a well-known experiment, Wöhler heated ‘inorganic’ ammonium cyanate without air present. The reaction produced only ‘organic’ urea, $\text{CO(NH}_2)_2$. No other substances were produced in the reaction. What is the formula of the cyanate ion in ammonium cyanate?

Atoms, molecules and stoichiometry

Transition elements and their compounds are important as catalysts. In which process is a compound of a transition element used instead of the element itself?

Reaction kinetics

Use of the Data Booklet is relevant for this question. For which species are the counts of protons, neutrons and electrons all different?

Atomic structure

Ethene undergoes reaction with steam in the presence of sulfuric acid. $\text{C}_2\text{H}_4 + \text{H}_2\text{O} \rightarrow \text{CH}_3\text{CH}_2\text{OH}$ What kind of reaction is shown here?

Hydrocarbons

What is correct about all nucleophiles?

Chemical bonding

What is the total number of isomers, covering structural isomers and stereoisomers, that have the formula $\text{C}_4\text{H}_8$ and contain structures with $\pi$ bonding?

Hydrocarbons

The distinctive aroma of burnt sugar is partly due to the compound shown below. $\text{CH}_3-\text{C}(=\text{O})-\text{CHO}$ There are two functional groups in this compound. Which reagent reacts with both functional groups?

Carbonyl compounds

What sequence of reagents can be used in the laboratory to change propan-1-ol into 2-bromopropane?

Halogen compounds

A carbanion is an organic ion that has a negative charge on a carbon atom. A carbocation is an organic ion that has a positive charge on a carbon atom. What steps are involved in the mechanism of the reaction between aqueous sodium hydroxide and 2-bromo-2-methylbutane?

Halogen compounds

Which compound produces an organic product with a lower boiling point when it is heated under reflux with an excess of acidified potassium dichromate(VI)?

Hydroxy compounds

The Data Booklet should be used when answering this question. What volume of oxygen, at room temperature and pressure, is required for the complete combustion of $0.1\text{ mol}$ of ethanol?

Atoms, molecules and stoichiometry

Cyclohexene, displayed below, is able to make an addition polymer. Which structure shows part of the polymer containing two cyclohexene residues?

Chemical bonding

If methanoic acid is one of the two reactants used, how many isomeric esters, including structural isomers and stereoisomers, can be formed with the molecular formula $\text{C}_5\text{H}_{10}\text{O}_2$?

Carboxylic acids and derivatives

The first six ionisation energies for four elements are shown below. Which element is most likely to belong to Group IV of the Periodic Table?

The Periodic Table: chemical periodicity

$\text{CCl}_2\text{FCClF}_2$ may be changed into $\text{CH}_2\text{FCF}_3$ by the route shown below. Stage 1: $\text{CCl}_2\text{FCClF}_2 \rightarrow \text{CCl}_2\text{CF}_3$ Stage 2: $\text{CCl}_2\text{CF}_3 \rightarrow \text{CCl}_2\text{FCF}_3$ Stage 3: $\text{CCl}_2\text{FCF}_3 \rightarrow \text{CH}_2\text{FCF}_3$ What type of reaction occurs in stage 1?

Halogen compounds

The upward thrust of a space shuttle was produced by the following reaction between aluminium and ammonium perchlorate. $10\text{Al} + 6\text{NH}_4\text{ClO}_4 \rightarrow 4\text{Al}_2\text{O}_3 + 2\text{AlCl}_3 + 12\text{H}_2\text{O} + 3\text{N}_2$ Which of the statements about this reaction are correct?

Electrochemistry

The Data Booklet is needed for this question. Which statements are correct for the atoms $^{23}\text{Na}$ and $^{24}\text{Mg}$?

Atomic structure

The pathway diagram for a reversible reaction is shown below. Which of the statements are correct?

Chemical energetics

Which diagrams show part of a giant molecular structure?

Chemical bonding

The solids W, X, Y and Z are compounds made from two different Group II metals. Their uses are outlined below. Compound W is used to make refractory linings in kilns. Compound X is used as a building material. It may also be heated in a kiln to produce compound Y. If Y is hydrated, it becomes compound Z, which is used in agriculture to treat soils. Which of the following statements about these compounds are correct?

Group 2

J is a solid element. It is present as an impurity in fossil fuels. Its oxide K is produced in car engines. In the atmosphere, K can be oxidised further to L. Which of the following statements about J, K and L are correct?

Electrochemistry

When methane is brominated, the free radical $\text{CH}_3\boldsymbol{\cdot}$ is formed. One possible termination stage for this reaction is the production of $\text{C}_2\text{H}_6$ when two free radicals combine. What could be produced in a terminating step during the bromination of propane?

Reaction kinetics

Fabrics used for aircraft seating are given a coating that contains a halogenoalkane. Why is this coating applied?

Halogen compounds

A liquid X is known to be either a single organic compound or a mixture of organic compounds. When X is treated with sodium, hydrogen gas is released. When X is treated with 2,4-dinitrophenylhydrazine reagent, orange crystals are formed. Which deductions about X can definitely be made?

An introduction to AS Level organic chemistry

The diagram shows, at a specified temperature, the Boltzmann distribution of the kinetic energies of the molecules in a mixture of two gases that react with each other. The activation energy for the reaction, $E_a$, is indicated. The dotted curves below illustrate the Boltzmann distribution for the same reaction at a higher temperature. In these diagrams, H denotes the activation energy at the higher temperature. Which diagram is correct?

Reaction kinetics

Ethanoic acid, $\text{CH}_3\text{CO}_2\text{H}$, is an important chemical used in the industrial production of rayon and aspirin. Which processes can be used to prepare ethanoic acid?

Carboxylic acids and derivatives

Crotonaldehyde, $\text{CH}_3\text{CH}={CHCHO}$, may be prepared by oxidising butadiene, $\text{CH}_2=\text{CHCH}=\text{CH}_2$, with air or oxygen. In one process, a blend of butadiene and oxygen is passed through a hot aqueous solution of palladium(II) ions, $\text{Pd}^{2+}(aq)$, which act as the catalyst for the reaction. Which statement is not correct about the role of the $\text{Pd}^{2+}(aq)$ ions?

Reaction kinetics

Which one is least similar to an ideal gas at room temperature and pressure?

States of matter

The Data Booklet is needed for this question. When $0.15\,\text{g}$ of an organic compound is vaporised, it takes up a volume of $65.0\,\text{cm}^3$ at $405\,\text{K}$ and $1.00 \times 10^5\,\text{N m}^{-2}$. Using the equation $pV = nRT$, which of the following expressions should be used to work out the relative molecular mass, $M_r$, of the compound?

Atoms, molecules and stoichiometry

Which compound is the only substance that is a gas at room temperature and pressure?

States of matter

Which formula shows the empirical formula of a compound?

Atoms, molecules and stoichiometry