Oct/Nov 2010

Each year, millions of tonnes of chlorine and sodium hydroxide are produced by the electrolysis of brine in a ‘diaphragm cell’. What is the function of the diaphragm in such a cell?

Electrochemistry

For the reaction that produces ethyl ethanoate from ethanol and ethanoic acid, the equilibrium constant, $K_c$, has a value of $4.0$ at $60^{\circ}\text{C}$. $\text{C}_2\text{H}_5\text{OH} + \text{CH}_3\text{CO}_2\text{H} \rightleftharpoons \text{CH}_3\text{CO}_2\text{C}_2\text{H}_5 + \text{H}_2\text{O}$ If $1.0\,\text{mol}$ of ethanol and $1.0\,\text{mol}$ of ethanoic acid are left to establish equilibrium at $60^{\circ}\text{C}$, how many moles of ethyl ethanoate will be produced?

Equilibria

Which equation shows the change associated with the enthalpy change of atomisation of iodine?

Chemical energetics

Camphor is a white solid that was used in the manufacture of early plastic celluloid. The mass percentage of hydrogen in camphor is the same as the mass percentage of oxygen. What is the molecular formula of camphor?

Atoms, molecules and stoichiometry

Why does phosphorus have a higher first ionisation energy than silicon?

The Periodic Table: chemical periodicity

On heating magnesium nitrate, $\text{Mg(NO}_3\text{)}_2\cdot7\text{H}_2\text{O}$, which three gases are released?

Group 2

In soil, the ammonium sulfate found in nitrogenous fertilisers can be oxidised slowly by air to form sulfuric acid, nitric acid and water. How many moles of oxygen gas are required to completely oxidise one mole of ammonium sulfate?

Atoms, molecules and stoichiometry

Chile saltpetre, $\text{NaNO}_3$, has sodium iodide present as an impurity. Aqueous silver nitrate is added to an aqueous solution of Chile saltpetre. After this, concentrated aqueous ammonia is added. What observations would be seen?

Equilibria

Which statement describes the halogens chlorine, bromine and iodine?

Group 17

Sulfur dioxide is employed to bleach wood pulp in paper manufacture. It is also added as an additive in the making of jam and marmalade, usually in the form of sulfite compounds. If its amount exceeds $10\ \text{mg kg}^{-1}$, it has to be declared as an ingredient in the jam. What is the reason for adding sulfur dioxide to jam?

Nitrogen and sulfur

Which property of beryllium and its compounds is characteristic of the elements beneath it in Group II?

Group 2

An ion $X^+$ has eight protons. What electronic configuration does $X^+$ have?

Atomic structure

A feature of addition polymerisation is that the empirical formulae for the polymer and for its monomer are identical. The absorbent material used in babies’ disposable nappies is made from the addition polymer shown. Which monomer could this addition polymer have been formed from?

Chemical bonding

Compound X reacts with ethanoic acid, with a $\text{H}^+$ catalyst present, to form the compound shown below. What is the molecular formula of compound X?

Hydroxy compounds

Compound Y shows all of the following properties. • It exists as a liquid at $25\,^\circ\text{C}$. • It is fully miscible with water. • It undergoes reaction with aqueous sodium hydroxide. What might Y be?

Carboxylic acids and derivatives

Tartaric acid occurs in some wines. It can be made in the laboratory in two steps. $\text{OHCCHO} \xrightarrow{\text{step 1}} \text{intermediate} \xrightarrow{\text{step 2}} \text{HO}_2\text{CCH(OH)CH(OH)CO}_2\text{H}$ Which reagents may be suitable for this synthesis?

Organic synthesis

Which alcohol forms just one possible oxidation product when it is warmed with dilute acidified potassium dichromate(VI)?

Hydroxy compounds

Limonene is an oil produced in the peel of citrus fruits. When limonene reacts with an excess of bromine, $\text{Br}_2\text{(l)}$, at room temperature in the dark, which product is formed?

Halogen compounds

Lactic acid is present naturally, for example in sour milk. State one property of lactic acid.

Equilibria

Which compound would be expected to undergo nucleophilic addition?

Carbonyl compounds

Which compound undergoes a substitution reaction by the $\text{S}_\text{N}1$ mechanism?

Reaction kinetics

The compound 2-methylpropene, $\text{C}_4\text{H}_8$, is a monomer that is used to make synthetic rubber. Apart from 2-methylpropene, there are $x$ more isomers of $\text{C}_4\text{H}_8$ that have a double bond, whether they are structural isomers or otherwise. Determine the value of $x$.

Chemical bonding

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

Chemical energetics

Which environmental problem is not worsened by the emission of oxides of nitrogen from car engines?

Nitrogen and sulfur

Ethanol is produced by reacting ethene gas with steam in the presence of phosphoric(V) acid. $\text{C}_2\text{H}_4(\text{g}) + \text{H}_2\text{O}(\text{g}) \rightleftharpoons \text{C}_2\text{H}_5\text{OH}(\text{g}) \qquad \Delta H = -45\,\text{kJ mol}^{-1}$ This reaction is performed at $570\,\text{K}$ and $60\,\text{atm}$. What would happen if the reaction were carried out at the same temperature but under a pressure of $200\,\text{atm}$?

Equilibria

The diagram shows the Boltzmann distribution for molecular energies at a particular temperature. Which factor that affects the rate of a reaction can be explained by this Boltzmann distribution?

Reaction kinetics

What kinds of intermolecular forces may be present between neighbouring urea molecules?

Chemical bonding

Separate samples of calcium and barium are each placed into beakers of cold water that contain a few drops of litmus solution. Which observation is seen with calcium only, and not with barium?

Group 2

Disproportionation refers to a reaction in which one reactant is oxidised and reduced at the same time. Which of the incomplete equations below show disproportionation?

Electrochemistry

Element X is a solid and is present as a contaminant in carbonaceous fuels. Its oxide Y is produced in car engines. In the atmosphere, Y may undergo further oxidation to Z. Which of the following statements about Y and Z are correct?

Nitrogen and sulfur

The diagram illustrates the structure of the naturally occurring molecule cholesterol. Which of the following statements about cholesterol are correct?

Hydroxy compounds

Glyceraldehyde, $\text{HOCH}_2\text{CH(OH)CHO}$, is produced in photosynthesis and has one chiral carbon atom. Which reagents react with glyceraldehyde to give an organic product that has no chiral carbon atom?

Carbonyl compounds

An organic compound turns aqueous bromine colourless and, on reaction with sodium, gives hydrogen. Which molecular formula could this compound have?

Hydroxy compounds

Sulfur dioxide, $\text{SO}_2$, is used in wines to stop ethanol being oxidised by air. To find the amount of $\text{SO}_2$, a wine sample is titrated using iodine, $\text{I}_2$. For this reaction, 1 mole of $\text{SO}_2$ is oxidised by 1 mole of $\text{I}_2$. By how much does the oxidation number of sulfur change in this reaction?

Electrochemistry

Aircraft textiles are given a finish that includes a halogenoalkane. Why is this done?

Chemical bonding

Nickel accounts for $20\%$ of the coin’s total mass. The coin has a mass of $10.0\,\text{g}$. How many nickel atoms are in the coin?

Atoms, molecules and stoichiometry

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

Organic nitrates present in photochemical smog may lead to breathing difficulties. The diagram illustrates one organic nitrate molecule. Which answer gives the bond angles shown in ascending order (smallest first)?

Chemical bonding

Standard enthalpy changes of combustion may be used to calculate enthalpy changes of formation. The equation below shows the standard enthalpy change of formation of butane. $4\text{C(s)} + 5\text{H}_2(\text{g}) \rightarrow \text{C}_4\text{H}_{10}(\text{g})$ Using the standard enthalpy of combustion data given below, determine the value of the standard enthalpy change of formation, $\Delta H_f^\circ$, for this reaction.

Chemical energetics

During a calorimetric experiment, $1.60\,\text{g}$ of a fuel is burnt. $45\%$ of the energy released is absorbed by $200\,\text{g}$ of water, causing its temperature to increase from $18^{\circ}\text{C}$ to $66^{\circ}\text{C}$. The specific heat capacity of water is $4.2\,\text{J g}^{-1}\text{K}^{-1}$. What is the total energy released per gram of fuel burnt?

Chemical energetics

The tendency of an atom in a covalent bond to draw electrons towards itself is known as electronegativity. The larger the electronegativity difference between the two atoms in the bond, the more polar the bond becomes. Which pair would produce the most polar covalent bond between the atoms?

Chemical bonding

Which molecule or structure does not include three atoms joined at an angle between $109^\circ$ and $110^\circ$?

Chemical bonding

A dimer, X, remains stable in the solid state, whereas in solution a dynamic equilibrium is established. $\text{X(aq)} \rightleftharpoons 2\text{Y(aq)}$ A solution of X initially has a concentration of $0.50\,\text{mol dm}^{-3}$. Once equilibrium is attained, $[\text{X(aq)}]$ has decreased to $0.25\,\text{mol dm}^{-3}$. The way in which $[\text{X(aq)}]$ and $[\text{Y(aq)}]$ vary with time is shown on a graph until equilibrium is reached. The value of $K_c$ is then worked out. Which graph and $K_c$ value are correct?

Equilibria

Equivalent molar amounts of magnesium carbonate and strontium carbonate are heated separately so that complete thermal decomposition occurs. The lowest temperature at which this takes place is called $T_d$. After cooling, the residues are each added to the same volumes of water, and the pH change is recorded. This pH change is called $\Delta \text{pH}$. Which metal has the larger value of $T_d$, and the larger value of $\Delta \text{pH}$?

Group 2

In aqueous solution, the acid HIO undergoes disproportionation as shown in the equation below, where $m$, $n$, $p$ and $q$ are the smallest whole numbers in their simplest ratio. $m\text{HIO} \rightarrow n\text{I}_2 + p\text{HIO}_3 + q\text{H}_2\text{O}$ Oxidation numbers may be used to balance this equation. What are the values of $n$ and $p$?

Electrochemistry

What mass of solid residue may be produced by the thermal decomposition of $4.10\,\text{g}$ of anhydrous calcium nitrate?

Atoms, molecules and stoichiometry

Which statement accounts for the observation that magnesium hydroxide dissolves in aqueous ammonium chloride, but does not dissolve in aqueous sodium chloride?

Equilibria

What is observed when chlorine is passed through aqueous potassium iodide?

Electrochemistry

Strontium metal may be produced by electrolysing molten strontium bromide, $\text{SrBr}_2$, using the apparatus illustrated in the diagram. Why is an argon atmosphere used around the cathode?

Electrochemistry

Which of the following statements about bromine is correct?

Group 17

Concentrated sulfuric acid reacts with solid sodium chloride at room temperature, and it also reacts with solid sodium iodide at room temperature. Which row correctly describes the way concentrated sulfuric acid behaves in each reaction?

Group 17

Which diagram depicts the Boltzmann distribution of molecular energies for $T_1$ and $T_2$, given that $T_1 = 300\,\text{K}$ and $T_2 = 310\,\text{K}$?

Reaction kinetics

What is the number of structural isomers of trichloropropane, $\text{C}_3\text{H}_5\text{Cl}_3$?

Halogen compounds

There are nine compounds with molecular formula $\text{C}_4\text{H}_8\text{Br}_2$. Which compound can be prepared from an alkene by an addition reaction?

Hydrocarbons

If ethanal, $\text{CH}_3\text{CHO}$, undergoes reaction with HCN and the resulting organic product is then hydrolysed using aqueous acid, organic compound Y is produced. If propanal, $\text{C}_2\text{H}_5\text{CHO}$, is heated under reflux with acidified potassium dichromate(VI), organic compound Z is produced. What is the difference between the relative molecular masses of compounds Y and Z?

Atoms, molecules and stoichiometry

Which reagent sequence may be used in the laboratory to change propan-1-ol into 2-bromopropane?

Hydroxy compounds

Esters are often employed as solvents and also as flavouring agents in fruit drinks and confectionery. An ester $\text{C}_8\text{H}_{12}\text{Br}_2\text{O}_4$ may be made in low yield through the reaction shown. $\text{CH}_3\text{C(Br)(CH}_2\text{Br)CO}_2\text{H} + (\text{CH}_3)_2\text{C(OH)CO}_2\text{H} \rightarrow \text{C}_8\text{H}_{12}\text{Br}_2\text{O}_4 + \text{H}_2\text{O}$ What structural formula represents the ester $\text{C}_8\text{H}_{12}\text{Br}_2\text{O}_4$?

Chemical bonding

Although many organic reactions need heating before they happen, this is not true for all of them. Which reaction takes place at a satisfactory rate at room temperature $(20^\f)$?

Reaction kinetics

Which pair of reagents will undergo a redox reaction?

Electrochemistry

The diagram illustrates part of the structure of strobilurin, a fungicide. R and R' denote inert groups. After strobilurin is heated with aqueous sulfuric acid, and the product obtained is then exposed to hydrogen in the presence of a palladium catalyst, what might be the structure of the final product?

Organic synthesis

Fluoroalkenes are employed in the manufacture of polymers such as poly(vinyl)fluoride (PVF). PVF is used to produce non-flammable aircraft interiors. The diagram below shows the repeat unit of PVF. What is the skeletal formula of the monomer that forms PVF?

Chemical bonding

$\text{CH}_3\text{CH}_2\text{COCH}_2\text{CH}_3$ reacts with hydrogen cyanide and produces a cyanohydrin. Which characteristic applies to the product?

Carbonyl compounds

The table shows the radii, in pm, for several ions. $[1\,\text{pm} = 10^{-12}\,\text{m}]$ Caesium chloride, $\text{CsCl}$, has a lattice arrangement that is unlike both sodium chloride, $\text{NaCl}$, and magnesium oxide, $\text{MgO}$. Which factor seems to decide the lattice type of these three compounds?

Chemical bonding

Which of the compounds shown contain chiral carbon atoms?

An introduction to AS Level organic chemistry

When ammonia, $\text{NH}_3$, is prepared in a school or college laboratory, it is usually dried before it is collected. Which drying agents can be used to dry ammonia?

States of matter

Zirconium, $\text{Zr}$, proton number 40, is a metal used to make corrosion-resistant alloys. Zirconium metal is obtained from the oxide $\text{ZrO}_2$ by the reaction sequence shown below. reaction 1: $\text{ZrO}_2 + 2\text{Cl}_2 + 2\text{C} \rightarrow \text{ZrCl}_4 + 2\text{CO}$ reaction 2: $\text{ZrCl}_4 + 2\text{Mg} \rightarrow \text{Zr} + 2\text{MgCl}_2$ Which of these statements about this extraction process are correct?

The Periodic Table: chemical periodicity

Which of the following statements about covalent bonds are correct?

Chemical bonding

A student pours $10\ \text{cm}^3$ of $0.100\ \text{mol dm}^{-3}$ sulfuric acid into one test-tube and $10\ \text{cm}^3$ of $0.100\ \text{mol dm}^{-3}$ ethanoic acid into a second test-tube. He then adds $1.0\ \text{g}$ (an excess) of magnesium ribbon to each test-tube and records suitable measurements. Both acids start at the same temperature. Neither reaction is finished after 2 minutes, but both are complete after 20 minutes. Which of the following statements are correct?

Reaction kinetics

How are the main reactions in the Haber and Contact processes alike?

Equilibria

A car that uses lead-free fuel is fitted with a catalytic converter in its exhaust system. Analysis of the exhaust gases shows that small amounts of nitrogen oxides are present. Which changes would lead to a lower concentration of nitrogen oxides in the exhaust?

Nitrogen compounds

The diagram illustrates a compound found in smoke produced by burning garden waste. Which reagents would show a colour change when they react with this compound?

Analytical techniques

Organic acids and alcohols can react with each other to make esters. Which combinations of compounds could give a product with molecular formula $\text{C}_4\text{H}_6\text{O}_4$?

Atoms, molecules and stoichiometry

This question requires use of the Data Booklet. In an organic synthesis, the product is obtained in a $62\%$ yield. Which of the following conversions agrees with this information?

Atoms, molecules and stoichiometry

Methanol can be produced by allowing carbon monoxide to react with hydrogen. $\text{CO(g)} + 2\text{H}_2\text{(g)} \rightarrow \text{CH}_3\text{OH(g)}$ The average bond energies needed are listed below. $E(\text{C} \equiv \text{O}) = 1077\,\text{kJ mol}^{-1}$ $E(\text{C-O}) = 360\,\text{kJ mol}^{-1}$ $E(\text{C-H}) = 410\,\text{kJ mol}^{-1}$ $E(\text{H-H}) = 436\,\text{kJ mol}^{-1}$ $E(\text{O-H}) = 460\,\text{kJ mol}^{-1}$ Calculate the enthalpy change for this reaction.

Chemical energetics

The reaction pathway diagram below is displayed. Which of these reactions would produce a profile like this?

Reaction kinetics

Which solid is formed from a simple molecular lattice?

States of matter

The reaction pathway diagram shown below displays the energies of the reactants, products and the transition state in a reaction. Which expression shows the activation energy for the forward reaction?

Chemical energetics

Flask X holds $5\,\text{dm}^3$ of helium at a pressure of $12\,\text{kPa}$, while flask Y holds $10\,\text{dm}^3$ of neon at a pressure of $6\,\text{kPa}$. When the flasks are connected and the temperature is kept constant, what final pressure is reached?

States of matter

The enthalpy change of formation, $\Delta H_f$, for hydrated calcium ions is the enthalpy change for the reaction below. $\text{Ca(s)} + \text{aq} - 2e^- \rightarrow \text{Ca}^{2+}(\text{aq})$ These enthalpy changes are not given in the Data Booklet. $\text{Ca(s)} \rightarrow \text{Ca(g)} \quad \Delta H_a = 177\,\text{kJ mol}^{-1}$ $\text{Ca}^{2+}(\text{g}) + \text{aq} \rightarrow \text{Ca}^{2+}(\text{aq}) \quad \Delta H_{hyd} = -1565\,\text{kJ mol}^{-1}$ Calculate the enthalpy change of formation of hydrated calcium ions.

Chemical energetics

In a mixture of concentrated nitric and sulfuric acids, the equilibrium shown below is established. $\text{HNO}_3 + \text{H}_2\text{SO}_4 \rightleftharpoons \text{H}_2\text{NO}_3^+ + \text{HSO}_4^-$ Which row gives the correct description of how each substance behaves in the equilibrium mixture?

Equilibria

A monatomic ion $X^+$ has eight protons. What is the electronic configuration of $X^+$?

Atomic structure

For the reaction that produces ethyl ethanoate from ethanol and ethanoic acid, the equilibrium constant, $K_c$, has a value of $4.0$ at $60^{\circ}\text{C}$. $\text{C}_2\text{H}_5\text{OH} + \text{CH}_3\text{CO}_2\text{H} \rightleftharpoons \text{CH}_3\text{CO}_2\text{C}_2\text{H}_5 + \text{H}_2\text{O}$ If $1.0\,\text{mol}$ of ethanol and $1.0\,\text{mol}$ of ethanoic acid are left to attain equilibrium at $60^{\circ}\text{C}$, how many moles of ethyl ethanoate are produced?

Equilibria

Enthalpy changes of combustion may be applied to work out enthalpy changes of formation. The equation below shows the enthalpy change of formation of butane. $4\text{C}(s) + 5\text{H}_2(g) \rightarrow \text{C}_4\text{H}_{10}(g)$ Using the standard enthalpy of combustion data given below, what is the numerical value of the standard enthalpy change of formation, $\Delta H_f^{\circ}$, for this reaction?

Chemical energetics

During a calorimetry experiment, $1.60\,\text{g}$ of a fuel is burnt. $45\%$ of the energy given out is taken in by $200\,\text{g}$ of water, and its temperature increases from $18^{\circ}\text{C}$ to $66^{\circ}\text{C}$. The specific heat capacity of water is $4.2\,\text{J g}^{-1}\,\text{K}^{-1}$. What is the total energy released for each gram of fuel burnt?

Chemical energetics

Which equation describes the process associated with the enthalpy change of atomisation of iodine?

Chemical energetics

Camphor is a white solid and was used in the manufacture of the early plastic celluloid. Camphor contains equal percentages by mass of hydrogen and oxygen. What is the molecular formula of camphor?

Atoms, molecules and stoichiometry

Within the soil, ammonium sulfate in nitrogenous fertilisers may be oxidised slowly by air, giving sulfuric acid, nitric acid and water. What number of moles of oxygen gas is required to completely oxidise one mole of ammonium sulfate?

Atoms, molecules and stoichiometry

What is the reason that the first ionisation energy of phosphorus is greater than the first ionisation energy of silicon?

The Periodic Table: chemical periodicity

When magnesium nitrate, $\text{Mg(NO}_3)_2\cdot7\text{H}_2\text{O}$, is heated, which three gases are released?

Group 2

Sulfur dioxide is employed to bleach wood pulp during paper manufacture. It is also used as an additive in making jam and marmalade, often in the form of sulfite compounds. If it is present in amounts greater than $10\ \text{mg kg}^{-1}$, it must be listed as an ingredient of the jam. What is the purpose of adding sulfur dioxide to jam?

Electrochemistry

Which property of beryllium and its compounds is characteristic of the elements further down Group II?

Group 2

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

Chemical energetics

Compound Y shows all of these properties: It is a liquid at $25\,^\circ\text{C}$. It is completely miscible with water. It reacts with aqueous sodium hydroxide. What could Y be?

Carboxylic acids and derivatives

A feature of addition polymerisation is that the empirical formulae of the polymer and its monomer are identical. The absorbent material used in babies’ disposable nappies is produced from the addition polymer shown. From which monomer could this addition polymer be made?

Chemical bonding

In the presence of an $\text{H}^+$ catalyst, compound X reacts with ethanoic acid to form the compound shown. What molecular formula does compound X have?

Hydroxy compounds

Limonene is an oil present in the peel of citrus fruits. Which product is formed when an excess of bromine, $\text{Br}_2(l)$, reacts with limonene at room temperature in the dark?

Hydrocarbons

Tartaric acid occurs in certain wines. It can be prepared in the laboratory in two stages. $\text{OHCCHO} \xrightarrow{\text{step 1}}$ intermediate $\xrightarrow{\text{step 2}} \text{HO}_2\text{CCH(OH)CH(OH)CO}_2\text{H}$. Which reagents would be suitable for this synthesis?

Organic synthesis

When warmed with dilute acidified potassium dichromate(VI), which alcohol produces just one oxidation product?

Hydroxy compounds

Lactic acid is found naturally, for instance in sour milk. What is a characteristic of lactic acid?

Carboxylic acids and derivatives

Which compound would take part in nucleophilic addition?

Carbonyl compounds

Which compound is involved in an $\text{S}_\text{N}1$ substitution reaction?

Reaction kinetics

The compound 2-methylpropene, $\text{C}_4\text{H}_8$, is a monomer that is used to make synthetic rubber. Besides 2-methylpropene, there are $x$ further isomers of $\text{C}_4\text{H}_8$, whether structural or other types, that contain a double bond. Determine the value of $x$.

Chemical bonding

Which ion contains a greater number of electrons than protons, and a greater number of protons than neutrons? $[\text{H} = ^1_1\text{H};\; \text{D} = ^2_1\text{H};\; \text{O} = ^{16}_8\text{O}]$

Atomic structure

Which environmental problem is not aggravated by oxides of nitrogen released from car engines?

Nitrogen and sulfur

Which kinds of intermolecular forces may be present between neighbouring urea molecules?

States of matter

Ethanol is produced by combining ethene gas with steam in the presence of phosphoric(V) acid. $\text{C}_2\text{H}_4(g) + \text{H}_2\text{O}(g) \rightleftharpoons \text{C}_2\text{H}_5\text{OH}(g) \qquad \Delta H = -45\,\text{kJ mol}^{-1}$ This reaction is carried out at $570\,\text{K}$ and $60\,\text{atm}$. If the reaction were done at the same temperature but at a pressure of $200\,\text{atm}$, what consequences would there be?

Equilibria

The diagram shows the Boltzmann distribution for molecular energies at a particular temperature. Which factor that affects the rate of a reaction can be accounted for by this Boltzmann distribution?

Reaction kinetics

Disproportionation is the name given to a reaction in which a reactant is oxidised and reduced at the same time. Which of the incomplete equations below illustrate disproportionation?

Electrochemistry

Separate samples of calcium and barium are each put into beakers of cold water that contain a few drops of litmus solution. Which observations will be seen with calcium only and not with barium?

Group 2

The diagram illustrates the structure of the naturally occurring molecule cholesterol. Which of the following statements about cholesterol are correct?

Hydroxy compounds

Element X is solid. It is present as an impurity in carbonaceous fuels. Its oxide Y is produced in car engines. Y may be further oxidised to Z in the atmosphere. Which statements about Y and Z are correct?

Nitrogen and sulfur

An organic compound turns aqueous bromine colourless and reacts with sodium to release hydrogen. Which molecular formula could be the one for this compound?

Hydroxy compounds

Why are textiles intended for aircraft coated with a finish that includes a halogenoalkane?

Halogen compounds

Sulfur dioxide, $\text{SO}_2$, is introduced into wines so that ethanol is not oxidised by air. To find the quantity of $\text{SO}_2$, a wine sample is titrated using iodine, $\text{I}_2$. In this reaction, one mole of $\text{SO}_2$ is oxidised by one mole of $\text{I}_2$. What change in oxidation number does sulfur undergo in this reaction?

Electrochemistry

Glyceraldehyde, $\text{HOCH}_2\text{CH(OH)CHO}$, is produced during photosynthesis and has a chiral carbon atom. Which reagents would react with glyceraldehyde to form an organic product that does not contain a chiral carbon atom?

Carbonyl compounds

Use of the Data Booklet is needed for this question. Nickel accounts for $20\%$ of the coin's total mass. The coin has a mass of $10.0\,\text{g}$. How many nickel atoms are present in the coin?

Atoms, molecules and stoichiometry

Organic nitrates in photochemical smog may lead to difficulty in breathing. The diagram displays one example of an organic nitrate molecule. In which order should the bond angles shown be arranged in ascending order (smallest first)?

Chemical bonding

Each year, millions of tonnes of both chlorine and sodium hydroxide are produced by electrolysing brine in a ‘diaphragm cell’. What is the function of the diaphragm in such a cell?

Electrochemistry

Which statement gives the correct description of the halogens chlorine, bromine and iodine?

Group 17

Chile saltpetre, $\text{NaNO}_3$, has sodium iodide as an impurity. Aqueous silver nitrate is added to an aqueous solution of Chile saltpetre. Concentrated aqueous ammonia is then added. Which observations would be seen?

Group 17