May/June 2025

ICl$_3$ undergoes a redox reaction with water. $v\text{ICl}_3 + w\text{H}_2\text{O} \rightarrow x\text{HCl} + y\text{HI} + z\text{HIO}_3 + z\text{HClO}_3$ Which values of $v$, $x$ and $z$ produce the correctly balanced equation?

Electrochemistry

Dinitrogen tetroxide, $\text{N}_2\text{O}_4$, undergoes reversible decomposition. $\text{N}_2\text{O}_4 \rightleftharpoons 2\text{NO}_2 \qquad \Delta H = +58.0\,\text{kJ mol}^{-1}$ A mixture at equilibrium containing $\text{N}_2\text{O}_4$ and $\text{NO}_2$ gases is introduced into a closed container in standard conditions. $K_c = 1.15 \times 10^{-1}\,\text{mol dm}^{-3}$ The conditions are then altered. With the revised conditions, $K_c = 1.70 \times 10^{3}\,\text{mol dm}^{-3}$. Which change in conditions has taken place?

Equilibria

$50\,\text{cm}^3$ of $1.0\,\text{mol dm}^{-3}$ $\text{H}_2\text{SO}_4$ is poured into $100\,\text{cm}^3$ of $1.0\,\text{mol dm}^{-3}$ NaOH in an insulated container. Before they are combined, both solutions are at $20\,^\circ\text{C}$. Once mixed, the temperature increases, and the maximum temperature reached is $29\,^\circ\text{C}$. Assume that: - every joule of energy released by the reaction is used to increase the temperature of the aqueous reaction mixture - the specific heat capacity of the mixture is $4.2\,\text{J cm}^{-3}\,\text{K}^{-1}$. What is the enthalpy of neutralisation value obtained from this experiment?

Chemical energetics

Barium dithionate, $\text{BaS}_2\text{O}_6\cdot2\text{H}_2\text{O}$, dissolves in water. $\text{S}_2\text{O}_6^{2-}$ ions decompose slowly in acidic solution. $\text{S}_2\text{O}_6^{2-}(\text{aq}) \rightarrow \text{SO}_2(\text{g}) + \text{SO}_4^{2-}(\text{aq})$ A mass of $3.513\,\text{g}$ of $\text{BaS}_2\text{O}_6\cdot2\text{H}_2\text{O}$ is dissolved in water in a $100\,\text{cm}^3$ volumetric flask, and the flask is then filled to the mark with $\text{HCl(aq)}$. At time $x$ min, a white precipitate with mass $0.661\,\text{g}$ is present in the flask. Calculate the concentration of $\text{BaS}_2\text{O}_6$ in the volumetric flask at time $x$ min?

Reaction kinetics

The diagram depicts two containers of methane joined by a closed tap. Each container has a volume of $1.00\,\text{m}^3$. Left container: $16\,\text{g}$ methane at $100\,\text{kPa}$. Right container: $96\,\text{g}$ methane at $200\,\text{kPa}$. The tap is opened. The temperature of the system is altered to $800\,\text{K}$. The system then reaches a constant pressure. What pressure does the methane have within the system?

States of matter

Which of the following statements about a $3p$ orbital is correct?

Atomic structure

In which pair do both species: - have the same shape - have the same number of covalent bonds?

Chemical bonding

An equation for a reaction involving ammonium ions is given below. $\text{NH}_4^+ + \text{OH}^- \rightleftharpoons \text{NH}_3 + \text{H}_2\text{O}$ There are four statements about this reaction. 1. The ammonium ions are reduced. 2. For the reverse reaction, ammonia behaves as a Brønsted-Lowry base. 3. The ammonium ion and the ammonia molecule possess the same bond angle. 4. This reaction is not a redox reaction. Which statements are correct?

Equilibria

On the surface of a catalytic converter, which reduction process takes place?

Nitrogen and sulfur

Three statements concerning the halogens, chlorine, bromine and iodine, as well as their compounds, are given below. 1. The halogen with the highest boiling point has atoms that make the strongest bond with hydrogen. 2. The halogen with the strongest instantaneous dipole (id-id) attractions produces the most thermally stable hydrogen halide. 3. The most volatile element oxidises hydrogen most quickly. Which of the statements are correct?

Chemical bonding

Which reagent or reagents, together with the required conditions, will oxidise chlorine, $\text{Cl}_2$, to a compound in which chlorine has the +5 oxidation state?

Electrochemistry

The reaction between a reactive metal and an excess of a dilute acid is studied. The total volume of hydrogen gas formed is measured at intervals of $30$ seconds over a period of $3$ minutes. The mean rate of reaction in the first $30$ seconds is $P$. The mean rate of reaction in the final $30$ seconds is $Q$. What is the value of $P - Q$?

Reaction kinetics

Which diagram represents the electronegativity of the elements Na, Mg, Al and Si when this is plotted against their first ionisation energies?

The Periodic Table: chemical periodicity

Radium is an element that lies beneath barium in Group 2 of the Periodic Table. Which equation represents the change when solid radium nitrate, $\text{Ra(NO}_3)_2$, is heated strongly?

Group 2

The table presents some information about the elements in Period 3 of the Periodic Table. Which of the statements is correct?

The Periodic Table: chemical periodicity

Each mineral named here acts as a blend of two carbonate compounds. They may serve as fire retardants because, on heating, they break down to give $\text{CO}_2$. This gas then helps to extinguish the fire. barytocite, $\text{BaCa(CO}_3)_2$ dolomite, $\text{CaMg(CO}_3)_2$ huntite, $\text{Mg}_3\text{Ca(CO}_3)_4$ What is the ranking of fire-retardant effectiveness, from most effective to least effective?

Atoms, molecules and stoichiometry

Compound X is made up of two Period 3 elements, Y and Z. When Compound X reacts with water, it forms only two products: a hydroxide that is slightly soluble and compound Q. Q is a compound containing element Z and hydrogen. When compound Q burns in moist air, it produces an oxide and water. In the oxide, element Z has an oxidation number of $+5$. Which row gives the identities of element Y and element Z?

The Periodic Table: chemical periodicity

The three reagents below are given. 1 aqueous sodium carbonate 2 $\text{LiAlH}_4$ 3 water Which of these reagents will react with pure ethanoic acid to form a solution that contains ethanoate ions?

Equilibria

When compound T undergoes complete combustion, the only products are carbon dioxide and water. With $\text{PCl}_5$, compound T gives steamy fumes. Compound T shows no visible product with 2,4-dinitrophenylhydrazine reagent. What can be deduced with certainty from this evidence?

Hydroxy compounds

Some details about carbonyl compound X are provided. • When X is treated with $\text{LiAlH}_4$, a secondary alcohol is formed. • If X is reacted with alkaline $\text{I}_2 (aq)$, a yellow precipitate is produced. Which compound is X?

Carbonyl compounds

An organic compound J reacts with excess sodium to form an organic ion carrying a charge of $-3$. J also reacts with excess $\text{NaOH} (aq)$ to form an organic ion carrying a charge of $-1$. What is the structural formula of J?

Hydroxy compounds

Which organic compound formula is produced when propanoic acid reacts with methanol, using concentrated sulfuric acid as a catalyst?

Carboxylic acids and derivatives

From the diagram, curve X was produced by recording the volume of oxygen given off during the decomposition of $100\ \text{cm}^3$ of $1.0\ \text{mol dm}^{-3}$ hydrogen peroxide. Manganese(IV) oxide was used as the catalyst. Which change to the initial experimental conditions would generate curve Y?

Reaction kinetics

Structural isomerism and stereoisomerism ought to be taken into account when answering this question. 2,5-dibromohexane is heated under reflux with ethanolic KOH. How many isomeric compounds are produced with molecular formula $\text{C}_6\text{H}_{10}$?

Hydrocarbons

If only structural isomers are considered, how many alcohols of each type have the formula $\text{C}_5\text{H}_{12}\text{O}$?

Hydroxy compounds

Which structure shows a section of the PVC polymer chain?

Chemical bonding

A suggested mechanism for the exothermic hydrolysis of 2-chloro-2-methylpropane is shown. Which diagram shows the reaction pathway diagram for this mechanism?

Chemical energetics

Compound W is made up of carbon, nitrogen and hydrogen atoms. When Compound W is reacted with $\text{HCl(aq)}$, propanoic acid is formed. Which row is correct?

Nitrogen compounds

Two reactions are given. 1. 2-bromo-2-methylbutane is heated with $\text{NaOH(aq)}$ 2. 2-chloro-2-methylbutane is heated with $\text{NaOH(aq)}$ The conditions are identical in both reactions, and $\text{NaOH(aq)}$ is present in excess. From $30.18\,\text{g}$ of 2-bromo-2-methylbutane, $12.32\,\text{g}$ of product X is produced. [$M_r$: 2-bromo-2-methylbutane, $150.9$; 2-chloro-2-methylbutane, $106.5$] Which row is the correct one?

Atoms, molecules and stoichiometry

An alkene P reacts with an excess of hot concentrated acidified $\text{KMnO}_4\text{(aq)}$. Methylpropanoic acid is the only organic product formed. Which alkene is P?

Hydrocarbons

Three substances are given below. 1. butane 2. hydrogen 3. hydrogen bromide Which substances could be formed in the free-radical substitution reaction between ethane and bromine?

Hydrocarbons

The diagram shows the structure of a testosterone molecule. Which of the following statements are correct?

Chemical bonding

The displayed structural formula for hept-1,4,5-triene is $\text{CH}_2\text{CHCH}_2\text{CHCCHCH}_3$. In one molecule of hept-1,4,5-triene, how many carbon atoms are $sp^2$ hybridised?

Chemical bonding

The first seven ionisation energies for an element lying between lithium and neon in the Periodic Table are given below. $1310\quad 3390\quad 5320\quad 7450\quad 11000\quad 13300\quad 71000\ \text{kJ mol}^{-1}$ What is the outer electronic configuration of this element?

The Periodic Table: chemical periodicity

Hydrocarbon X is a saturated compound. Each molecule has one ring made up of carbon atoms. The mass spectrum for hydrocarbon X has been recorded. The peak for the $\text{M}^+$ ion measures $14\,\text{mm}$ in height. The peak for the $[\text{M}+1]^+$ ion measures $0.77\,\text{mm}$ in height. What is the $m/e$ value of the $\text{M}^+$ ion of X?

Hydrocarbons

The equation for the reaction between hydrogen and oxygen is shown. $2\text{H}_2(g) + \text{O}_2(g) \rightarrow 2\text{H}_2\text{O}(l)$ Which expression represents the standard enthalpy change for this reaction?

Chemical energetics

$P$ is a compound that, when it burns in an excess of oxygen, produces only carbon dioxide and water. A sample of $2.20\ \text{g}$ of $P$ contains $1.20\ \text{g}$ of carbon and $0.20\ \text{g}$ of hydrogen. If $P$ is added to a solution of sodium carbonate, gas bubbles are observed. What is $P$?

Atoms, molecules and stoichiometry

Substance $W$ shows the physical properties listed below. Melting point $= 2072^\circ\text{C}$ Boiling point $= 2980^\circ\text{C}$ Electrical conductivity: poor (solid), good (liquid), insoluble in water. What substance is $W$?

Chemical bonding

Which diagram shows the lattice structure of sodium chloride?

Chemical bonding

An aqueous solution X contains the substance HQ, which acts as a weak acid. $\text{HQ(aq)} \rightleftharpoons \text{H}^+(\text{aq}) + \text{Q}^-(\text{aq})$ The soluble salt NaQ is then introduced into X. What effect does this have on the $[\text{H}^+(\text{aq})]$ and on the pH of X?

Equilibria

Examine the statements below. 1. Silicon dioxide has a greater melting point than sulfur dioxide. 2. Ammonia has a higher boiling point than phosphine, $\text{PH}_3$. Which of these statements is correct?

Chemical bonding

On average, the intermolecular forces in water are much stronger than the average intermolecular forces in steam. On average, the intermolecular forces in ice are a little stronger than the average intermolecular forces in water. The equilibrium processes shown are linked to enthalpy changes. $\text{H}_2\text{O}(l) \rightleftharpoons \text{H}_2\text{O}(g) \quad \Delta H_b$ $\text{H}_2\text{O}(s) \rightleftharpoons \text{H}_2\text{O}(l) \quad \Delta H_m$ Which statements are correct?

States of matter

An experiment is performed to find the value of $x$ in hydrated lithium hydroxide, $\text{LiOH}\cdot x\text{H}_2\text{O}$. A portion of the solid is heated in a crucible using a Bunsen flame. The sample is fully dehydrated; no decomposition occurs. mass of empty crucible / g = $Q$ mass of crucible with $\text{LiOH}\cdot x\text{H}_2\text{O}$ / g = $R$ mass of crucible and residue after heating / g = $S$ Which equation is used to obtain the correct value of $x$?

Atoms, molecules and stoichiometry

A sample of an ideal gas occupies $240\,\text{cm}^3$ at $37^\circ\text{C}$ and $100\,\text{kPa}$. Calculate the number of moles of gas in the sample.

States of matter

In certain conditions, $\text{CCl}_4$ and $\text{H}_2\text{O}$ undergo reaction as represented below. The activation energy for this reaction is $+62\,\text{kJ mol}^{-1}$. $\text{CCl}_4 + 2\text{H}_2\text{O} \rightarrow \text{CO}_2 + 4\text{HCl}$\quad $\Delta H = -61.5\,\text{kJ mol}^{-1}$ Which enthalpy profile diagram is the best match for this reaction?

Chemical energetics

A helium ion has two protons, two neutrons and one electron. This helium ion and a proton are each sent separately through a uniform electric field. The particles move at the same velocity. Which arrow shows the path of each particle?

Atomic structure

The skeletal formulae for arginine and lysine are shown. Which row is correct?

Chemical bonding

The oxide and the chloride of an element $X$ are each mixed separately with water. The two solutions formed have the same action on litmus. What might element $X$ be?

The Periodic Table: chemical periodicity

What is the reason that the halogens become less volatile as Group 17 is descended?

States of matter

Compound $M$ is a white solid. It is the chloride belonging to a Period 3 element. Details of some reactions that begin with compound $M$ are shown below. compound $M$ + non‑polar solvent → colourless solution compound $M$ added in small portions to water → steamy fumes, $Q$; colourless solution, $R$ fumes $Q$ tested with moist blue litmus paper → paper turns red solution $R$ + a few drops of $\text{NaOH(aq)}$ + excess $\text{NaOH(aq)}$ → white precipitate; dissolves to give a colourless solution What is compound $M$?

The Periodic Table: chemical periodicity

Which of the following statements about strontium and its compounds is true?

Group 2

How many neutrons are present in an iron atom that has a mass number of 60?

Atomic structure

Sodium bromide is heated with concentrated sulfuric acid. Which row shows the change in sulfur’s oxidation number and the function of the bromide ions in the reaction?

Electrochemistry

When ammonium chloride is mixed with calcium hydroxide, a reaction takes place. What function do the ammonium ions have in this reaction?

Equilibria

Elements Y and Z are both found in Period 3. Y is the Period 3 element with the smallest atomic radius. In Period 3, only two elements have a melting point lower than that of Z. Y and Z combine to make compound R. Which compound could R be?

The Periodic Table: chemical periodicity

$1.0\,\text{g}$ of each of four distinct compounds of Group 2 elements is heated so that thermal decomposition takes place. The solid residue from every decomposition is the oxide of the Group 2 element. The volume of gas released by each reaction is measured at room conditions. Which substance gives the greatest gas volume?

Atoms, molecules and stoichiometry

Sulfur dioxide in the atmosphere can lead to acid rain. This happens in two steps. 1 oxidation of $\text{SO}_2$ to $\text{SO}_3$ 2 formation of dilute $\text{H}_2\text{SO}_4$. Which row gives the atmospheric catalyst for step 1 and the reagent for step 2?

Nitrogen and sulfur

Which statement about the mechanism of an $\text{S}_\text{N}1$ reaction involving a halogenoalkane is correct?

Halogen compounds

The repeat unit of a polymer is shown. Three claims about this polymer are listed. Which claims are correct?

Chemical bonding

Methanoic acid, $\text{HCO}_2\text{H}$, shows acidic behaviour in the same way as other carboxylic acids. It is also oxidised by the same oxidising agents that can oxidise aldehydes. Which pair of compounds would lead to the same observations with Fehling’s reagent?

Electrochemistry

Which row shows pentanenitrile as one of the products?

Nitrogen compounds

An ester, $\text{R}'\text{CO}_2\text{R}''$, is hydrolysed under alkaline conditions. $\text{R}'$ and $\text{R}''$ are not the same alkyl groups. Which row shows the two products that are produced?

Carboxylic acids and derivatives

The diagram illustrates a Boltzmann distribution for molecular energies in a gaseous reaction at two temperatures and two activation energies. Which pairing of temperature and activation energy would produce the greatest reaction rate?

Reaction kinetics

Which compound is not oxidised by acidified potassium dichromate(VI) solution, yet does react with sodium metal?

Hydroxy compounds

Butan-2-one undergoes reaction with alkaline $\text{I}_2\text{(aq)}$. After that, excess dilute sulfuric acid is added to the reaction mixture. The organic products formed in this reaction sequence are triiodomethane and product M. What is product M?

Carbonyl compounds

Four reagents are given below. 1 aqueous $\text{KCl}$ 2 dilute $\text{HCl}$ 3 liquid $\text{SOCl}_2$ 4 solid $\text{PCl}_5$. Which of these reagents, when added to ethanol, would quickly generate a gas that makes blue litmus turn red?

Hydroxy compounds

Four separate drops of 1-chlorobutane, 1-bromobutane and 1-iodobutane are each introduced into three test-tubes containing $1.0\,\text{cm}^3$ of aqueous silver nitrate at $60^\circ\text{C}$. In each instance, hydrolysis occurs. $\text{H}_2\text{O(l)} + \text{R-X(l)} + \text{Ag}^+\text{(aq)} \rightarrow \text{R-OH(aq)} + \text{AgX(s)} + \text{H}^+\text{(aq)}$. $\text{R}$ represents $\text{C}_4\text{H}_9$ and $\text{X}$ represents the halogen atom. The rate at which cloudiness forms in the test-tubes is in the order $\text{RCl} < \text{RBr} < \text{RI}$. Why does this happen?

Halogen compounds

Propanoic acid is reduced by $\text{LiAlH}_4$ to form organic product P. Methanoic acid then reacts with organic product P, with a few drops of concentrated sulfuric acid present, to form organic product Q. What are the skeletal formulae of these two organic products?

Chemical bonding

A mixture of the gases $\text{CH}_3\text{Cl}$ and $\text{Cl}_2$ is exposed to ultraviolet light. Which compound is formed in a termination step of the reaction?

Reaction kinetics

Propan-1-ol, $\text{C}_3\text{H}_7\text{OH}$, is dehydrated by passing its vapour over hot aluminium oxide, producing a hydrocarbon. Which structural formula shows the product formed when this hydrocarbon reacts with bromine?

Chemical bonding

Alkane S has the molecular formula $\text{C}_4\text{H}_{10}$. In sunlight, S reacts with $\text{Cl}_2(g)$ to form just two distinct monochloroalkanes, $\text{C}_4\text{H}_9\text{Cl}$. Each of these monochloroalkanes is then heated with ethanolic $\text{KOH}$. In both cases, the same alkene T is formed, with no additional organic products. What is formed when T is reacted with hot concentrated acidified $\text{KMnO}_4$?

Hydrocarbons

When structural isomers and stereoisomers are both counted, how many isomers does $\text{C}_2\text{H}_2\text{Br}_2$ have?

Halogen compounds

Which compound displays stereoisomerism?

Chemical bonding

The equation for the reaction of sulfur dioxide with oxygen is shown below. $\text{2SO}_2(g) + \text{O}_2(g) \rightleftharpoons \text{2SO}_3(g) \quad \Delta H = -197\,\text{kJ mol}^{-1}$ A closed container is charged with $1.0\,\text{mol}$ of $\text{SO}_2$ and $1.0\,\text{mol}$ of $\text{O}_2$, then the mixture is heated and kept at a steady temperature. When equilibrium is reached at this temperature, the equilibrium mixture contains $0.8\,\text{mol}$ of $\text{SO}_3$. Which statement is correct?

Equilibria

In the mass spectrum of $\text{CH}_3\text{Cl}$, a molecular ion peak, $\text{M}^+$, appears at $m/e = 50$ with a relative abundance of $18.0\%$. There are also other peaks in the spectrum. What peak is observed at $m/e = 52$?

Analytical techniques

'Red lead' is a red pigment whose formula is $\text{Pb}_3\text{O}_4$. Every formula unit of 'red lead' is identical. A formula unit contains three lead ions and four oxide ions. In 'red lead', lead has two different oxidation states. State the oxidation states of lead in 'red lead'.

Atoms, molecules and stoichiometry

Some standard enthalpy of combustion data are provided. From these data, determine the enthalpy change of formation of methanol.

Chemical energetics

Which row is the correct one?

The Periodic Table: chemical periodicity

In the Haber process, the two gaseous reactants must react in the presence of a catalyst made from a transition element. State the metal and the mole ratio in which the gases combine?

Chemistry of transition elements

In aqueous solution, hydrogen peroxide, $\text{H}_2\text{O}_2$, decomposes to form water and oxygen when an appropriate catalyst is present. $50\,\text{cm}^3$ of a $0.50\,\text{mol dm}^{-3}$ hydrogen peroxide solution gave $120\,\text{cm}^3$ of oxygen in $2.0$ minutes. The gas volume was recorded at room conditions. Calculate the average rate at which hydrogen peroxide decomposed over this $2.0$ minute interval.

Reaction kinetics

Which uncombined gaseous atom contains a total of five electrons in spherically shaped orbitals?

Atomic structure

Why does sodium have a higher second ionisation energy than magnesium?

The Periodic Table: chemical periodicity

$\text{BF}_3$ reacts with $\text{NH}_3$ to produce a lone compound with a simple molecular structure. $\text{BF}_3 + \text{NH}_3 \rightarrow \text{F}_3\text{B--NH}_3$ Which row shows how the bond angles alter during the reaction?

Chemical bonding

The equation for nitrogen reacting with hydrogen is given below. $\text{N}_2(\text{g}) + 3\text{H}_2(\text{g}) \rightleftharpoons 2\text{NH}_3(\text{g}) \qquad \Delta H_r^\circ = -92.2\,\text{kJ mol}^{-1}$ Which statement is correct?

Equilibria

Hydrogen peroxide, $\text{H}_2\text{O}_2$, breaks down into water and oxygen when an appropriate catalyst is introduced. $20.0\,\text{cm}^3$ of aqueous hydrogen peroxide decomposes and gives $600\,\text{cm}^3$ of oxygen under room conditions. What is the concentration of the aqueous hydrogen peroxide?

Atoms, molecules and stoichiometry

A $0.15\,\text{g}$ sample of an organic compound is turned into vapour and then takes up a volume of $65.0\,\text{cm}^3$ at $405\,\text{K}$ and $1.00 \times 10^5\,\text{Pa}$. By applying $pV = nRT$, which equation should be used to find the relative molecular mass, $M_r$, of the compound?

Atoms, molecules and stoichiometry

One of the ingredients in a washing powder is sodium hydrogencarbonate, $\text{NaHCO}_3$. During a titration, $1.00\,\text{g}$ of the washing powder is found to need $7.15\,\text{cm}^3$ of $0.100\,\text{mol dm}^{-3}$ sulfuric acid for the reaction to go to completion. Sodium hydrogencarbonate is the only substance in the washing powder that reacts with the acid. Determine the percentage by mass of sodium hydrogencarbonate in the washing powder?

Atoms, molecules and stoichiometry

The flow chart illustrates some reactions involving nitrogen compounds. gas 1 $\xrightarrow{\text{acid}}$ salt 1 $\xrightarrow{\text{alkali}}$ salt 2 + other products Which row correctly identifies gas 1 and salt 2?

Nitrogen and sulfur

When aqueous silver nitrate is mixed with aqueous sodium chloride, a precipitate is formed. Which reagent, when added to this mixture, results in a colourless solution?

Analytical techniques

Which of the statements is correct?

Group 2

Which statement concerning the properties of halogens and hydrogen halides is correct?

Group 17

Diagram 1 illustrates the reaction pathway for a reaction. Diagram 2 shows a graph of reactant concentration against time for the same reaction. Which diagrams, when drawn to the same scale, display the effect of a higher temperature on this reaction?

Reaction kinetics

Three statements concerning the chemical periodicity of Period 3 oxides are given. 1. The highest oxidation state shown by the Period 3 elements in their oxides rises from sodium to phosphorus, then falls from phosphorus to sulfur. 2. The oxides from sodium to aluminium dissolve in water with no hydrolysis; from silicon to sulfur they undergo hydrolysis by water. 3. The structure and bonding change from giant ionic to giant covalent to simple molecular. Which statements are correct?

Chemical bonding

Which dot-and-cross diagrams show molecules that can react with unburned hydrocarbons to produce peroxyacetyl nitrate, PAN, a constituent of photochemical smog?

Nitrogen and sulfur

Which group of three elements includes one element that has both the highest melting point and the lowest electrical conductivity among the three elements in the group

The Periodic Table: chemical periodicity

In which row do the particles become larger? smallest $\rightarrow$ largest

Atoms, molecules and stoichiometry

W, X, Y and Z are Group 2 elements: barium, calcium, magnesium and strontium, although not necessarily in that sequence. W reacts with dilute hydrochloric acid more quickly than Y does. The hydroxide of X is less soluble in water than the hydroxide of W. The sulfate of Y is the most soluble among the sulfates of W, X, Y and Z. At the same temperature, the carbonate of Z decomposes more slowly than the carbonate of W. What is the $M_r$ of the nitrate of W?

Group 2

Polymer J contains the repeat unit $[-\text{CH}(-\text{C}_2\text{H}_5)\text{CH}(-\text{CH}_3)-]$. Polymer K contains the repeat unit $[-\text{CH}(-\text{CH}_3)\text{CH}(-\text{CH}_3)-]$. Which row is correct?

Chemical bonding

$0.200\text{ mol}$ ethanenitrile is allowed to react with excess dilute sodium hydroxide. Only organic compound S and ammonia gas are formed. The yield for this reaction is $80.0\%$. What mass of S is produced?

Atoms, molecules and stoichiometry

The structure of butenedioic acid is given below. If excess $\text{NaOH(aq)}$ is added to butenedioic acid, what organic product is produced?

Carboxylic acids and derivatives

Four organic compounds are shown. A mixture containing these four compounds is reacted with hot aqueous sodium hydroxide. The products from this reaction are then acidified. Which organic acids are present in the products?

Carboxylic acids and derivatives

Ethanal undergoes reaction with KCN dissolved in liquid HCN. An intermediate is formed during this reaction. Which statement is correct?

Carbonyl compounds

The equation represents the overall reaction of an amine with an acid chloride. $\text{2CH}_3\text{CH}_2\text{NH}_2 + \text{CH}_3\text{CH}_2\text{COCl} \rightarrow \text{CH}_3\text{CH}_2\text{CONHCH}_2\text{CH}_3 + \text{CH}_3\text{CH}_2\text{NH}_3\text{Cl}$ The mechanism can be divided into four steps, listed below. Which of these steps are Brønsted-Lowry acid-base reactions?

Equilibria

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

Carbonyl compounds

All of the compounds illustrated are made by plants. Every compound is heated with acidified $\text{K}_2\text{Cr}_2\text{O}_7$. Which compound would produce an observation that is different from the other three?

Electrochemistry

When answering this question, take both structural isomerism and stereoisomerism into account. How many alcohols with molecular formula $\text{C}_5\text{H}_{12}\text{O}$ produce a yellow precipitate with alkaline $\text{I}_2\text{(aq)}$?

Hydroxy compounds

The reaction below produces an amine. $\text{C}_2\text{H}_5\text{I} + 2\text{NH}_3 \rightarrow \text{C}_2\text{H}_5\text{NH}_2 + \text{NH}_4\text{I}$ What is the mechanism?

Halogen compounds

The reaction below may be used to extend a carbon chain. $\text{CH}_3\text{CH}_2\text{CH}_2\text{Br} + \text{CN}^- \rightarrow \text{CH}_3\text{CH}_2\text{CH}_2\text{CN} + \text{Br}^-$ Which row gives the correct reagent and conditions for carrying out this reaction?

Halogen compounds

Which row gives the products produced when cyclohexene reacts with acidified $\text{KMnO}_4$ under different conditions?

Hydrocarbons

Two stages of the free-radical substitution reaction between methane and chlorine are given below. step 1 $\text{CH}_3\boldsymbol{\cdot} + \text{Cl}_2 \rightarrow \text{CH}_3\text{Cl} + \text{Cl}\boldsymbol{\cdot}$ step 2 $\text{CH}_3\text{Cl} + \text{Cl}\boldsymbol{\cdot} \rightarrow \text{CH}_2\text{Cl}\boldsymbol{\cdot} + \text{HCl}$ Which statement is the correct one?

Reaction kinetics

Compound P exhibits cis/trans isomerism and forms a red-brown precipitate with Fehling’s solution. What is P?

Carbonyl compounds

Fructose is a sugar containing more than one chiral centre. The fructose molecule is shown below, with X, Y and Z marking three carbon atoms. Which carbon atoms are chiral centres?

An introduction to AS Level organic chemistry

Organic compound T contains only a single functional group. The empirical formula of compound T is $\text{C}_2\text{H}_4\text{O}$. Some functional groups are listed below. 1 alcohol 2 aldehyde 3 ester 4 ketone Which functional groups are possible for compound T?

Atoms, molecules and stoichiometry

Chromium is contained in compound $X$. • When 2 moles of compound $X$ react with exactly 3 moles of silicon. • The only substances formed in this reaction are 4 moles of chromium and 3 moles of a silicon compound in which silicon has oxidation state $+4$. • In this reaction, chromium and silicon are the only elements whose oxidation states change. What could compound $X$ be?

Electrochemistry

An organic compound gives a mass spectrum with the following characteristics. • The molecular ion peak appears at $m/e = 60$. Its relative intensity = 100. • A peak is present at $m/e = 61$, and its relative intensity = 2.2. • No fragment peak is seen at $m/e = 17$. • A fragment peak is observed at $m/e = 31$. What may be the identity of the organic compound?

Analytical techniques

At a temperature of $450\,^\circ\text{C}$, the reversible reaction below has reached equilibrium. $\text{H}_2 + \text{I}_2 \rightleftharpoons \text{2HI} \qquad \Delta H = -9.5\,\text{kJ mol}^{-1}$ The table gives the equilibrium concentrations in the reaction mixture. $[\text{H}_2] = 1.02\,\text{mol dm}^{-3}$, $[\text{I}_2] = 0.02\,\text{mol dm}^{-3}$, $[\text{HI}] = 0.98\,\text{mol dm}^{-3}$. The temperature of the reaction mixture is raised while the volume stays constant. Under these conditions, the concentration of one component decreases to $0.80\,\text{mol dm}^{-3}$ at equilibrium. What is the concentration of $\text{H}_2$ in the new equilibrium mixture?

Equilibria

The initial step in the industrial manufacture of nitric acid starting from ammonia is shown by this equation. $4\text{NH}_3(\text{g}) + 5\text{O}_2(\text{g}) \rightleftharpoons 4\text{NO}(\text{g}) + 6\text{H}_2\text{O}(\text{g})$ By using the standard enthalpy change of formation data below, determine the value of the standard enthalpy change, $\Delta H^\circ$, for this reaction.

Chemical energetics

The gaseous compound $Z$ breaks down when heated. The diagram shows Boltzmann distributions for $Z$ at two different temperatures, $P$ and $Q$. The lines $X$ and $Y$ show the activation energies for the decomposition of $Z$ with and without a catalyst. At the higher temperature and with a catalyst present, which curve and which line represent the decomposition of $Z$?

Reaction kinetics

The arrangement of a molecule present in food is shown. Four statements about the molecule are given. Which two of the statements are correct?

An introduction to AS Level organic chemistry

As it melts, in which substance do covalent bonds break?

Chemical bonding