Oct/Nov 2016

The diagram shows, at one particular 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

The table gives the partial pressures for an equilibrium mixture produced by the Haber process. $3\text{H}_2(g) + \text{N}_2(g) \rightleftharpoons 2\text{NH}_3(g)$ What is the numerical value of the equilibrium constant, $K_p$, for this reaction?

Equilibria

An autocatalytic reaction is one in which one of the products acts as a catalyst for the reaction. Which curve would be produced if the rate of an autocatalytic reaction is plotted against time?

Reaction kinetics

To react completely, $1.15\,\text{g}$ of a metallic element requires $300\,\text{cm}^3$ of oxygen at $298\,\text{K}$ and $1\,\text{atm}$ pressure, producing an oxide containing $\text{O}^{2-}$ ions. Which metallic element could this be?

Atoms, molecules and stoichiometry

The diagram displays the melting points of eight elements that have successive atomic numbers. Which element might be sodium?

The Periodic Table: chemical periodicity

A comparison is made of the properties of chlorine, bromine and their compounds. Which property is lower for chlorine than for bromine?

Group 17

In a motor vehicle's catalytic converter at $550^{\circ}\text{C}$, nitrogen dioxide reacts with unburnt hydrocarbon fragments such as $\text{CH}_3\bullet$. $4\text{CH}_3\bullet + 7\text{NO}_2 \rightarrow 3\frac{1}{2}\text{N}_2 + 4\text{CO}_2 + 6\text{H}_2\text{O}$ The table below shows different types of energy change for this reaction together with possible explanations for each one. Which row states the energy change for this reaction and the explanation for it?

Chemical energetics

When magnesium nitrate, $\text{Mg(NO}_3)_2$, is heated, it breaks down to form a white solid together with a mixture of gases. One of the gases given off is an oxide of nitrogen, $X$. $7.4\,\text{g}$ of anhydrous magnesium nitrate is heated until no further change occurs. What mass of $X$ is formed?

Atoms, molecules and stoichiometry

Compound $T$ is a white crystalline solid. When a sample of $T$ was combined with aqueous sodium hydroxide and heated, a pungent-smelling gas was released that turned damp red litmus paper blue. The same gas also formed dense white smoke with hydrogen chloride gas. Additional testing of a solution of $T$ using barium chloride solution gave a dense white precipitate that remained insoluble after dilute hydrochloric acid was added to the mixture. What is the identity of compound $T$?

Nitrogen and sulfur

Which row in the table shows the correct comparisons between the solubilities of calcium and barium hydroxide and the thermal stabilities of calcium and barium carbonate?

Group 2

$X$, $Y$ and $Z$ are three different halogens. The table gives the outcomes of nine experiments in which aqueous solutions of $X_2$, $Y_2$ and $Z_2$ were added separately to distinct aqueous solutions containing $X^-$, $Y^-$ and $Z^-$ ions. Which row in the table below shows the ions $X^-$, $Y^-$ and $Z^-$ arranged in decreasing order of their reducing power?

Electrochemistry

In the ideal gas equation, $pV = nRT$, which units are used for $n$ and $T$?

States of matter

In 1865, Kekulé proposed a ring arrangement for benzene, $\text{C}_6\text{H}_6$, with one hydrogen atom bonded to each carbon atom. Under this arrangement, every bond stays in the positions indicated. If benzene really had this structure, how many isomers of dichlorobenzene, $\text{C}_6\text{H}_4\text{Cl}_2$, would there be?

Hydrocarbons

The diagram illustrates the structure of vitamin A. How many chiral centres are there in a single vitamin A molecule?

Chemical bonding

PVC can be troublesome to dispose of. Two possible ways are burial in landfill sites and disposal by burning. Which row in the table is the correct one?

Polymerisation

A section of the structure of a fungicide, strobilurin, is shown below. R and R' are inert groups. In this reaction, strobilurin is heated with aqueous sulfuric acid, forming compound X. Compound X is then reacted with hydrogen in the presence of a nickel catalyst, giving compound Y. What could the structure of compound Y be?

Organic synthesis

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 form the intermediate, $Q$, from chloroethane?

Halogen compounds

$X$, $Y$ and $Z$ are three alcohol isomers. $X$: $\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{OH}$ $Y$: $\text{CH}_3\text{CH}_2\text{CH(OH)}\text{CH}_2\text{CH}_3$ $Z$: $(\text{CH}_3)_2\text{C(OH)CH}_2\text{CH}_3$ At least two of these alcohols undergo reaction with mild oxidising agents. If one of these alcohols is dehydrated, it will produce a pair of cis-trans isomers with molecular formula $\text{C}_5\text{H}_{10}$. Which row is right?

Hydroxy compounds

When propanone reacts with an aqueous mixture containing HCN and NaCN, the reaction follows a nucleophilic addition mechanism. In the first step of this mechanism, cyanide ions carry out the attack. Which diagram shows this correctly?

Carbonyl compounds

$P$, $Q$ and $R$ are carbonyl compounds. Fehling’s solution may be used to help distinguish these compounds. Which compounds produce a red-brown precipitate when warmed with Fehling’s solution?

Carbonyl compounds

Of the reactions given, which one would not form ethanoic acid?

Carboxylic acids and derivatives

Which formula shows an ester that, when hydrolysed with dilute sulfuric acid, produces propanoic acid?

Equilibria

When acidified dichromate(VI) ions, $\text{Cr}_2\text{O}_7^{2-}$, react with aqueous $\text{Fe}^{2+}$ ions, the dichromate(VI) ions are reduced to $\text{Cr}^{3+}$ ions. Which equation correctly represents this reaction?

Electrochemistry

Solvent X, which is used in printing inks, has the molecular formula $\text{C}_6\text{H}_{10}\text{O}_4$. It can be produced by reacting ethane-1,2-diol with ethanoic acid in the presence of an acid catalyst. The structure of ethane-1,2-diol is shown. Which structure shows solvent X?

Carboxylic acids and derivatives

A boron sample has aluminium as its sole impurity. A mass spectrum of the mixture displays three lines from three ions, $X^+$, $Y^+$ and $Z^+$. The information is: $m/e$: $X^+ = 10$, $Y^+ = 11$, $Z^+ = 27$ percentage abundance: $X^+ = 15.52$, $Y^+ = 74.48$, $Z^+ = 10.00$ Which of the following statements are correct?

Atomic structure

Which elements are able to form $\pi$ bonds in their compounds?

Chemical bonding

In which enthalpy changes is ΔH always negative?

Chemical energetics

During the production of sulfuric acid, this exothermic reaction takes place: $\text{2SO}_2(g) + \text{O}_2(g) \rightleftharpoons \text{2SO}_3(g)$ Which changes would shift the equilibrium position to the right?

Equilibria

Water is introduced to anhydrous aluminium chloride to prepare a $0.1\,\text{mol dm}^{-3}$ solution. Which statements are correct?

Equilibria

Catalytic converters are used to change the exhaust gases released by motor vehicles. Which reactions take place in catalytic converters?

Reaction kinetics

Which compounds would yield a carboxylic acid and a ketone when they are treated with hot, concentrated, acidified $\text{KMnO}_4$?

Hydrocarbons

Bromoethane reacts with NaOH in two different ways, depending on the solvent chosen. Which of these statements about the reactions are correct?

Halogen compounds

Several structural isomers of $\text{C}_3\text{H}_6\text{O}_3$ are shown below: $\text{HOCH}_2\text{COCH}_2\text{OH}$ $\text{HOCH}_2\text{CH(OH)CHO}$ $\text{HOCH}_2\text{CH}_2\text{CO}_2\text{H}$ $\text{CH}_3\text{CH(OH)CO}_2\text{H}$ Which statements concerning these structural isomers are correct?

Atoms, molecules and stoichiometry

Sodium azide, $\text{NaN}_3$, is an explosive that is used to inflate airbags in cars during crashes. It is made up of positive sodium ions and negative azide ions. What are the numbers of electrons in the sodium ion and the azide ion?

Atomic structure

If onions are peeled in air, the reaction below is believed to happen: $2\text{CH}_3\text{CH}_2\text{CH}=\text{S}=\text{O} + 2\text{H}_2\text{O} + 2[\text{O}] \rightarrow \text{H}_2\text{SO}_4 + \text{H}_2\text{S} + 2\text{CH}_3\text{CH}_2\text{CHO}$ Which of these tests would produce a positive result with the organic product?

Carbonyl compounds

The isotope $^{68}\text{Ge}$ has medical applications because it decays naturally to produce an isotope of another element, $^{68}\text{X}$, which can be used to detect tumours. This change in $^{68}\text{Ge}$ happens when an electron is taken into the nucleus and converts a proton into a neutron. Which statement correctly describes the composition of an atom of $^{68}\text{X}$?

Atomic structure

Histamine is made in the body to assist in combating infection. Its structure enables it to bind to receptors that widen blood vessels. What are the bond angles $x$, $y$ and $z$ in histamine, arranged from the smallest to the largest?

Chemical bonding

The table below shows the approximate percentage make-up of the atmospheres of four different planets. Which gas mixture has the highest density?

States of matter

One key reaction used in making nitric acid is the catalytic oxidation of ammonia. $4\text{NH}_3(g) + 5\text{O}_2(g) \rightarrow 4\text{NO}(g) + 6\text{H}_2\text{O}(g)$ For each mole of $\text{O}_2$ that undergoes this reaction, 181.8 kJ of energy is released. A factory produces $2.50 \times 10^5$ mol of NO per day. What quantity of energy, in kJ, is released each day?

Chemical energetics

Sodium chromate(VI), $\text{Na}_2\text{CrO}_4$, is produced by heating chromite, $\text{FeCr}_2\text{O}_4$, with sodium carbonate in an oxidising atmosphere. The ion present in chromite is $\text{Cr}_2\text{O}_4^{2-}$. $2\text{FeCr}_2\text{O}_4 + 4\text{Na}_2\text{CO}_3 + 3\frac{1}{2}\text{O}_2 \rightarrow 4\text{Na}_2\text{CrO}_4 + \text{Fe}_2\text{O}_3 + 4\text{CO}_2$ What is occurring in this reaction?

Electrochemistry

At a fixed temperature, $T_1$, the molecules in a gas have the molecular energy distribution shown in the diagram. If the temperature is raised to $T_2$, the distribution of molecular energies is altered. Which diagram shows this change correctly?

Reaction kinetics

Nitrogen combines with hydrogen to form ammonia. $\text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g)$ A reaction mixture containing $2.00$ mol of nitrogen, $6.00$ mol of hydrogen and $2.40$ mol of ammonia is left to attain equilibrium in a sealed vessel with a volume of $1\,\text{dm}^3$. It was determined that $2.32$ mol of nitrogen remained in the equilibrium mixture. Calculate the value of $K_c$.

Equilibria

At room temperature, lithium reacts with nitrogen to produce solid $\text{Li}_3\text{N}$. As shown, three vessels of equal volume are linked by taps A and B. Initially, A and B are closed; the left-hand vessel is evacuated, the middle vessel contains the reaction shown at equilibrium, and the right-hand vessel holds lithium only. Which action would result in the equilibrium mixture containing the greatest amount of ammonia?

Equilibria

The graph below illustrates how the first ionisation energy changes with proton number for some elements. The letters shown are not the normal symbols for the elements. Which statement about the elements is correct?

The Periodic Table: chemical periodicity

Which element has the strongest tendency to form covalent compounds?

Chemical bonding

Y and Z are both elements in Period 3. If the chloride of Y is put into water, it reacts to form a solution with pH $2$. If the chloride of Z is put into water, it dissolves and gives a solution with pH $7$. Which statement accounts for these observations?

Chemical bonding

When chlorine is reacted with hot aqueous sodium hydroxide, two chlorine-containing ions are produced. One of these is the chloride ion, $\text{Cl}^-$. Which other ion is formed?

Electrochemistry

J is a salt of one of the halogens chlorine, bromine, iodine or astatine. The reaction sequence below shows a set of reactions that uses a solution of J as the starting reagent. $\text{J(aq)} \xrightarrow[\text{AgNO}_3(aq)]{\text{HNO}_3(aq)}$ a precipitate $\xrightarrow[\text{dilute NH}_3(aq)]{\text{an excess of}}$ a colourless solution $\xrightarrow[\text{HNO}_3(aq)]{\text{an excess of}}$ a precipitate. Which salt could J be?

Group 17

On heating, magnesium nitrate decomposes. Which equation correctly shows the thermal decomposition of magnesium nitrate?

Group 2

Chlorine and bromine differ in volatility. Which row names the more volatile element, and states the correct reason?

Group 17

Water and ammonia react to form the ammonium ion. Which statement about this reaction is the correct one?

Equilibria

The diagram illustrates the reaction pathways with and without a catalyst. Which letter shows the overall energy difference for the reaction?

Chemical energetics

Limonene occurs in lemon and orange oils. When limonene is treated with an excess of dry hydrogen chloride, what is the main product?

Hydrocarbons

Rotundone is the compound that gives pepper its peppery smell and is also present in some red wines. How many hydrogen atoms are present in one molecule of rotundone?

Atoms, molecules and stoichiometry

The reaction $\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{Br} + \text{OH}^- \rightarrow \text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{OH} + \text{Br}^-$ follows an $\text{S}_\text{N}2$ mechanism. The reaction $(\text{CH}_3)_3\text{CBr} + \text{OH}^- \rightarrow (\text{CH}_3)_3\text{COH} + \text{Br}^-$ follows an $\text{S}_\text{N}1$ mechanism. Which statement about these two reactions is correct?

Reaction kinetics

The equation represents a reaction taking place between carbon monoxide and nitrogen monoxide in a catalytic converter. $2\text{CO}(g) + 2\text{NO}(g) \rightarrow 2\text{CO}_2(g) + \text{N}_2(g)$ Which statement is correct?

Electrochemistry

Which statement concerning stereoisomers is correct?

Chemical bonding

Which compound can be oxidised by acidified potassium manganate(VII) in order to form 3-methylpentan-2-one?

Electrochemistry

Ethane-1,2-diol, $\text{HOCH}_2\text{CH}_2\text{OH}$, is allowed to react with an excess of ethanoic acid, $\text{CH}_3\text{CO}_2\text{H}$, in the presence of an acid catalyst. This gives a compound with molecular formula $\text{C}_6\text{H}_{10}\text{O}_4$. What is the structure of this compound?

Carboxylic acids and derivatives

When Compound X is warmed with a mild oxidising agent, one of the reaction products will undergo reaction with hydrogen cyanide to produce 2-hydroxybutanenitrile. Which compound is X?

Carbonyl compounds

Which row gives the correct description of the reactivity of aldehydes and ketones?

Carbonyl compounds

Of the compounds shown, how many will react with aqueous sodium hydroxide to produce the sodium salt of a carboxylic acid?

Carboxylic acids and derivatives

For health reasons, people are recommended to consume less than $6.00\,\text{g}$ of salt (sodium chloride) each day. What mass of sodium is contained in $6.00\,\text{g}$ of sodium chloride?

Atoms, molecules and stoichiometry

Certain vegetable oils include ‘trans fats’, which are linked with unwanted rises in the level of cholesterol in the blood. In these oils, the word ‘trans’ refers, in the standard sense, to the positioning of groups across a $\text{C}=\text{C}$ double bond. In the diagrams below, $R_1$ and $R_2$ are different unbranched hydrocarbon chains. Which diagram correctly represents an optically active ‘trans fat’?

Chemical bonding

Photochromic lenses in spectacles become darker in bright sunlight because silver crystals are formed in the reaction shown below. $\text{Ag}^+ + \text{Cl}^- \rightarrow \text{Ag} + \text{Cl}$ Which of the statements below are correct for this reaction?

Electrochemistry

A cathedral in New Zealand has been made from cardboard. Cardboard is composed of polymer molecules. A section of one such polymer molecule is shown below. Which of these statements about this polymer are correct?

Chemical bonding

$X$ is an element with: • outer electrons in the 4th principal quantum shell, • a 1st ionisation energy that is greater than calcium's. Which element could $X$ be?

The Periodic Table: chemical periodicity

Methanol, $\text{CH}_3\text{OH}$, is manufactured industrially by the reaction of CO with $\text{H}_2$. $\text{CO}(g) + 2\text{H}_2(g) \rightleftharpoons \text{CH}_3\text{OH}(g) \quad \Delta H = -91\ \text{kJ mol}^{-1}$ The reaction may be carried out at $4 \times 10^3\ \text{kPa}$ and $1150\ \text{K}$. Which statements about this reaction are correct?

Equilibria

Equal masses of barium carbonate and magnesium carbonate powders are combined. The mixture is then heated in a Bunsen burner flame until no further change is seen. A gas is released. Which statements are correct?

Atoms, molecules and stoichiometry

Oxides of sulfur and oxides of nitrogen are both present in the atmosphere. Which of the following statements are correct?

Nitrogen and sulfur

A termite species makes a chemical defence secretion that contains the molecule shown below. To help work out the structure of this compound, it is reacted with hot, concentrated, acidified manganate(VII) ions. Which compounds are formed in this reaction?

Carboxylic acids and derivatives

1-bromopropane undergoes reaction with NaOH in different ways, depending on which solvent is used. Which of these statements about the reaction are correct?

Halogen compounds

The compound illustrated is formed when sugar burns. Which reagents would produce a positive test with this compound?

Analytical techniques

When copper reacts with a $50\%$ nitric acid solution, nitrogen monoxide is given off and a blue solution is formed. The balanced equation for this reaction is shown. $p\,\text{Cu} + q\,\text{HNO}_3 \rightarrow r\,\text{Cu(NO}_3)_2 + s\,\text{H}_2\text{O} + t\,\text{NO}$ What are the values of the integers $p$, $q$, $r$, $s$ and $t$?

Atoms, molecules and stoichiometry

Which of the following statements about how a carboxylic acid is formed are correct?

Carboxylic acids and derivatives

What electronic configuration does an isolated $\text{Ni}^{2+}$ ion have?

Atomic structure

On heating solid aluminium chloride, $\text{Al}_2\text{Cl}_6$ is produced. What type of bonding is present in $\text{Al}_2\text{Cl}_6$?

Chemical bonding

Which hydride has the least H-X-H bond angle?

Chemical bonding

During an experiment, a sample of a pure gas is placed in a gas syringe at a temperature of $300\,\text{K}$ and a pressure of $16\,\text{kPa}$. The gas is then compressed so that the volume it occupies is reduced by half. Once compression has taken place, the gas in the syringe has a temperature of $375\,\text{K}$ and a pressure of $40\,\text{kPa}$. Which statement is correct?

States of matter

In a calorimetric experiment $1.60\,\text{g}$ of a fuel is burnt. $45.0\%$ of the energy released is absorbed by $200\,\text{g}$ of water. The temperature of the water increases from $18.0\,^{\circ}\text{C}$ to $66.0\,^{\circ}\text{C}$. Calculate the total energy released per gram of fuel burnt (3 significant figures).

Chemical energetics

At a particular temperature, the diagram illustrates the Boltzmann distribution of the kinetic energies of the molecules in a mixture of two gases that react with each other. The reaction’s activation energy, $E_a$, is shown. The dotted curves underneath 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

The table gives the partial pressures in an equilibrium mixture made by the Haber process. Nitrogen: $7000\,\text{kPa}$ Hydrogen: $8000\,\text{kPa}$ Ammonia: $4000\,\text{kPa}$ $3\text{H}_2(g) + \text{N}_2(g) \rightleftharpoons 2\text{NH}_3(g)$ Determine the numerical value of the equilibrium constant, $K_p$, for this reaction?

Equilibria

An autocatalytic reaction is one in which a product catalyses the reaction. Which curve would be produced if the rate of an autocatalytic reaction were plotted against time?

Reaction kinetics

$1.15\,\text{g}$ of a metal requires $300\,\text{cm}^3$ of oxygen for complete reaction, at $298\,\text{K}$ and $1\,\text{atm}$ pressure, to produce an oxide containing $\text{O}^{2-}$ ions. Which metallic element could this be?

Atoms, molecules and stoichiometry

The diagram illustrates the melting points of eight elements whose atomic numbers are consecutive. Which one could be sodium?

The Periodic Table: chemical periodicity

A comparison is made between the properties of chlorine, bromine and the compounds they form. Which property is lower for chlorine than for bromine?

Group 17

At $550\,^{\circ}\text{C}$, nitrogen dioxide reacts with unburnt hydrocarbon fragments such as $\text{CH}_3\cdot$ inside the catalytic converter of a motor vehicle. $4\text{CH}_3\cdot + 7\text{NO}_2 \rightarrow 3\tfrac{1}{2}\text{N}_2 + 4\text{CO}_2 + 6\text{H}_2\text{O}$ The table below shows the kinds of energy change for this reaction together with possible explanations for these changes. Which row shows the energy change for this reaction and the explanation for it?

Chemical energetics

When magnesium nitrate, $\text{Mg(NO}_3)_2$, is heated, it breaks down to form a white solid together with a mixture of gases. One of the gases given off is an oxide of nitrogen, $X$. $7.4\,\text{g}$ of anhydrous magnesium nitrate is heated until the reaction is complete. What mass of $X$ is formed?

Atoms, molecules and stoichiometry

Compound $T$ is a white, crystalline solid. When a sample of $T$ was combined with aqueous sodium hydroxide and heated, a pungent-smelling gas was given off which turned damp red litmus paper blue. The same gas formed dense white smoke with hydrogen chloride gas. When a solution of $T$ was tested further with barium chloride solution, a dense white precipitate was formed, and this did not dissolve after dilute hydrochloric acid was added to the mixture. What is the identity of compound $T$?

Atoms, molecules and stoichiometry

Which table row correctly compares the solubilities of calcium and barium hydroxide, and the thermal stabilities of calcium and barium carbonate?

Group 2

$X$, $Y$ and $Z$ are three different halogens. The table records the outcomes of nine experiments in which aqueous solutions of $X_2$, $Y_2$ and $Z_2$ were each added separately to separate aqueous solutions containing $X^-,$ $Y^-$ and $Z^-$ ions. Which row in the table below lists the ions $X^-$, $Y^-$ and $Z^-$ in order of decreasing reducing strength?

Electrochemistry

In the ideal gas equation, $pV = nRT$, what units are used for $n$ and $T$?

States of matter

In 1865, Kekulé proposed a ring arrangement for benzene, $\text{C}_6\text{H}_6$, with one hydrogen atom bonded to each carbon atom. Within this arrangement, every bond stays in the positions indicated. If benzene really had this structure, how many isomers of dichlorobenzene, $\text{C}_6\text{H}_4\text{Cl}_2$, would be possible?

Chemical bonding

The diagram illustrates the structure of vitamin A. How many chiral centres are present in a single vitamin A molecule?

Chemical bonding

PVC is hard to dispose of. Two possible ways are placing it in landfill sites and disposing of it by combustion. Which row in the table is correct?

Polymerisation

A section of the structure of the fungicide strobilurin is displayed. $R$ and $R'$ are inert groups. In this sequence, strobilurin is heated with aqueous sulfuric acid to give compound $X$. Compound $X$ is then reacted with hydrogen in the presence of a nickel catalyst to form compound $Y$. What might the structure of compound $Y$ be?

Chemical bonding

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

Nitrogen compounds

$X$, $Y$ and $Z$ are three alcohol isomers. $X$: $\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{OH}$ $Y$: $\text{CH}_3\text{CH}_2\text{CH(OH)CH}_2\text{CH}_3$ $Z$: $(\text{CH}_3)_2\text{C(OH)CH}_2\text{CH}_3$ At least two of these alcohols undergo reaction with mild oxidising agents. If one of these alcohols is dehydrated, it forms a pair of cis-trans isomers with molecular formula $\text{C}_5\text{H}_{10}$. Which row is correct?

Hydroxy compounds

Propanone undergoes a nucleophilic addition mechanism when it reacts with an aqueous mixture of $\text{HCN}$ and $\text{NaCN}$. The first step in the mechanism is an attack by cyanide ions. Which diagram shows this correctly?

Carbonyl compounds

$P$, $Q$ and $R$ are carbonyl compounds. Fehling’s solution may be used to distinguish these compounds. Which compounds give a red-brown precipitate when warmed with Fehling’s solution?

Electrochemistry

Which reaction would not produce ethanoic acid?

Carboxylic acids and derivatives

Which formula shows an ester that will produce propanoic acid when it is hydrolysed with dilute sulfuric acid?

Carboxylic acids and derivatives

When acidified dichromate(VI) ions, $\text{Cr}_2\text{O}_7^{2-}$, react with aqueous $\text{Fe}^{2+}$ ions, the dichromate(VI) ions are reduced to $\text{Cr}^{3+}$ ions. Which equation correctly represents this reaction?

Electrochemistry

A solvent, X, that is used in printing inks has the molecular formula $\text{C}_6\text{H}_{10}\text{O}_4$. It can be prepared by reacting ethane-1,2-diol with ethanoic acid in the presence of an acid catalyst. What is the displayed formula of solvent X?

Chemical bonding

In a boron sample, aluminium is the sole impurity. The mass spectrum of the mixture has three peaks, which come from three ions, $X^+$, $Y^+$ and $Z^+$, with these results: $m/e$: $X^+ = 10$, $Y^+ = 11$, $Z^+ = 27$ Percentage abundance: $X^+ = 15.52$, $Y^+ = 74.48$, $Z^+ = 10.00$ Which of the following statements are true?

Atomic structure

Which elements are capable of making $\pi$ bonds in compounds?

Chemical bonding

For which enthalpy changes is the value of $\Delta H$ always less than zero?

Chemical energetics

During the production of sulfuric acid, this exothermic reaction takes place: $\text{2SO}_2(g) + \text{O}_2(g) \rightleftharpoons \text{2SO}_3(g)$ Which changes would shift the equilibrium position to the right?

Equilibria

Water is added to anhydrous aluminium chloride to prepare a $0.1\ \text{mol dm}^{-3}$ solution. Which of the following observations are correct?

Equilibria

Catalytic converters are used to alter exhaust emissions from motor vehicles. Which reactions take place in catalytic converters?

Reaction kinetics

When heated with hot, concentrated, acidified $\text{KMnO}_4$, which compounds would form a carboxylic acid and a ketone?

Hydrocarbons

Bromoethane undergoes reaction with NaOH in different ways, depending on which solvent is present. Which of these statements about the reactions are correct?

Halogen compounds

The structural isomers of $\text{C}_3\text{H}_6\text{O}_3$ shown below are: $\text{HOCH}_2\text{COCH}_2\text{OH}$ $\text{HOCH}_2\text{CH(OH)CHO}$ $\text{HOCH}_2\text{CH}_2\text{CO}_2\text{H}$ $\text{CH}_3\text{CH(OH)CO}_2\text{H}$ Which of the following statements about these structural isomers are correct?

Atoms, molecules and stoichiometry

Sodium azide, $\text{NaN}_3$, is an explosive that is used to fill airbags in cars during collisions. It is made up of positive sodium ions and negative azide ions. How many electrons are present in the sodium ion and the azide ion?

Atomic structure

The reaction believed to happen when onions are peeled in air is: $2\text{CH}_3\text{CH}_2\text{CHO} + 2\text{H}_2\text{O} + 2[\text{O}] \rightarrow \text{H}_2\text{SO}_4 + \text{H}_2\text{S} + 2\text{CH}_3\text{CH}_2\text{CHO}$ Which of these tests would produce a positive result with the organic product?

Carbonyl compounds

The $^{68}\text{Ge}$ isotope has medical applications because it undergoes a spontaneous radioactive change to form an isotope of a different element, $^{68}\text{X}$, which can be used to detect tumours. This change in $^{68}\text{Ge}$ happens when an electron enters the nucleus and turns a proton into a neutron. Which statement about the composition of an atom of $^{68}\text{X}$ is correct?

Atomic structure

Histamine is made in the body to assist in fighting infection. Its shape enables it to fit into receptors that widen blood vessels. What are the bond angles $x$, $y$ and $z$ in histamine, ordered from the smallest to the largest?

Chemical bonding

The table below shows the approximate percentages of gases in the atmospheres of four different planets. Which gas mixture has the highest density?

States of matter

A key reaction used in the production of nitric acid is the catalytic oxidation of ammonia. $4\text{NH}_3(g) + 5\text{O}_2(g) \rightarrow 4\text{NO}(g) + 6\text{H}_2\text{O}(g)$ For each mole of $\text{O}_2$ consumed in this reaction, $181.8\,\text{kJ}$ of energy are given out. A factory produces $2.50 \times 10^5\,\text{mol}$ of NO each day. What amount of energy, in kJ, is released in one day?

Chemical energetics

Sodium chromate(VI), $\text{Na}_2\text{CrO}_4$, is made by heating chromite, $\text{FeCr}_2\text{O}_4$, with sodium carbonate in an oxidising atmosphere. Chromite contains $\text{Cr}_2\text{O}_4^{2-}$ ions. $2\text{FeCr}_2\text{O}_4 + 4\text{Na}_2\text{CO}_3 + 3\tfrac{1}{2}\text{O}_2 \rightarrow 4\text{Na}_2\text{CrO}_4 + \text{Fe}_2\text{O}_3 + 4\text{CO}_2$ What is taking place in this reaction?

Electrochemistry