May/June 2022

Which atom has its outermost electron in an orbital with the shape shown, with principal quantum number 3?

Atomic structure

The reaction pathway diagram for aqueous sodium hydroxide reacting with dilute sulfuric acid is shown. What is the enthalpy change of neutralisation, $\Delta H_{\text{neut}}$, equal to?

Chemical energetics

A student carries out the reaction of $4\,\text{mol}$ of ammonia with oxygen to form only an oxide of nitrogen and water. In this reaction, each nitrogen atom has its oxidation state raised by $5$. What number of moles of oxygen gas reacts with $4\,\text{mol}$ of ammonia in this reaction?

Electrochemistry

During the treatment of domestic water supplies, chlorine is added to water to destroy bacteria. A small amount of $\text{ClO}^-$ ions is produced. When the $\text{ClO}^-$ ion is formed from aqueous chlorine, what change occurs in the oxidation number of chlorine?

Electrochemistry

Ethanoic acid is combined with ethanol. The ethanol contains a small quantity of methanol as an impurity. The equilibria below are set up. $\text{CH}_3\text{CO}_2\text{H}(l) + \text{CH}_3\text{CH}_2\text{OH}(l) \rightleftharpoons \text{CH}_3\text{CO}_2\text{CH}_2\text{CH}_3(l) + \text{H}_2\text{O}(l)$, $K_c = K_1$ $\text{CH}_3\text{CO}_2\text{H}(l) + \text{CH}_3\text{OH}(l) \rightleftharpoons \text{CH}_3\text{CO}_2\text{CH}_3(l) + \text{H}_2\text{O}(l)$, $K_c = K_2$ Which statement about the equilibrium mixture is correct?

Equilibria

$\text{SO}_3$ is produced from $\text{SO}_2$ and $\text{O}_2$ in the Contact process. This reaction is exothermic. Which row indicates the effect on the equilibrium yield in the Contact process of raising the temperature and of adding a vanadium(V) oxide catalyst?

Equilibria

The Boltzmann distribution for a gas held at a constant temperature of $50\,^{\circ}\text{C}$ is illustrated. When the gas temperature is lowered by $10\,^{\circ}\text{C}$, the graph alters its shape. What change occurs in the values of $n$ for the molecular energies X, Y and Z?

Reaction kinetics

A sample of $\text{Na}_2\text{CO}_3$ powder with a mass of $3.0\,\text{g}$ is mixed with $50\,\text{cm}^3$ of $1.0\,\text{mol dm}^{-3}$ HCl. The $\text{CO}_2$ collected has a volume of $600\,\text{cm}^3$. $\text{Na}_2\text{CO}_3(s) + 2\text{HCl}(aq) \rightarrow 2\text{NaCl}(aq) + \text{CO}_2(g) + \text{H}_2\text{O}(l)$ $[M_r: \text{Na}_2\text{CO}_3, 106.0]$ Under these same conditions, what volume of $\text{CO}_2$ would be formed if $1.0\,\text{g}$ of $\text{Na}_2\text{CO}_3$ powder were mixed into $50\,\text{cm}^3$ of $1.0\,\text{mol dm}^{-3}$ HCl?

Atoms, molecules and stoichiometry

When solid sodium iodide reacts with concentrated sulfuric acid, more than one sulfur-containing product is formed. What is the smallest oxidation number of sulfur in these products?

Group 17

Which of the following statements about the element in Period 3 and Group 13 of the Periodic Table is correct?

The Periodic Table: chemical periodicity

A student separately reacts $0.100\,\text{mol}$ of atoms of sodium, magnesium and phosphorus with an excess of oxygen. Which rows are correct?

Atoms, molecules and stoichiometry

Which atom has an electron count equal to that of the hydroxide ion, $\text{OH}^-$?

Atomic structure

A mixture consists only of magnesium carbonate and barium carbonate. A sample of this mixture is dissolved in nitric acid, forming a solution. How can this solution be treated so that a magnesium compound and a separate barium compound are obtained?

Group 2

Magnesium nitrate is heated in the apparatus illustrated. The pH of the liquid in the trough is then measured. The gas obtained is tested with a glowing splint. What results are observed?

Group 2

The results from tests carried out on a white crystalline solid, X, are shown in the table. X is heated gently: X sublimes. X is shaken with $\text{H}_2\text{O}$: a colourless solution, Y, is produced. Y is warmed with $\text{NaOH}(aq)$: a gas is evolved. $\text{AgNO}_3(aq)$ is added to Y: a white precipitate, Z, is produced. Z is shaken with $\text{NH}_3(aq)$: a colourless solution is formed. What is X?

Atoms, molecules and stoichiometry

Silicon is warmed in excess chlorine to form compound J. Then an excess of water is added to the sample of J that is obtained. Which row is correct?

Chemical bonding

Inside a catalytic converter, $5.6\,\text{g}$ of carbon monoxide react with an excess of nitrogen monoxide. What product is formed in this reaction?

Atoms, molecules and stoichiometry

Which reaction mixture gives off an acidic gas?

Group 17

Ethanol may be transformed into propanenitrile in two stages. $\text{CH}_3\text{CH}_2\text{OH} \xrightarrow{X} \text{CH}_3\text{CH}_2\text{Br} \xrightarrow{Y} \text{CH}_3\text{CH}_2\text{CN}$. What types of reaction are $X$ and $Y$?

Halogen compounds

Which compound reacts with $\text{LiAlH}_4$ to produce two optical isomers?

Carbonyl compounds

How many esters have molecular formula $\text{C}_4\text{H}_8\text{O}_2$?

Carboxylic acids and derivatives

Carbon monoxide, CO, nitrogen dioxide, $\text{NO}_2$, and sulfur dioxide, $\text{SO}_2$, are all pollutants in the atmosphere. Which reaction takes place in the atmosphere?

Equilibria

In separate experiments, $5.0\,\text{g}$ samples of four different s-block metals are each placed in an excess of water. The gas given off is collected, and its volume is measured under the same temperature and pressure conditions for every sample. Which metal gives the greatest volume of gas?

Atoms, molecules and stoichiometry

Oct-1-ene, $\text{CH}_3(\text{CH}_2)_5\text{CH}=\text{CH}_2$, is capable of being thermally cracked. Which of compounds W, X, Y and Z could be formed by thermally cracking oct-1-ene? W: $\text{CH}_2=\text{CH}_2$, X: $\text{CH}_3\text{CH}=\text{CH}_2$, Y: $\text{CH}_3\text{CH}_2\text{CH}_3$, Z: $\text{CH}_2=\text{CHCH}=\text{CH}_2$.

Chemical bonding

When answering this question, allow for structural isomerism and stereoisomerism. How many isomeric alkenes with formula $\text{C}_5\text{H}_8$ are found in the mixture formed when $1,4$-dibromopentane reacts with NaOH in ethanol?

Hydrocarbons

A halogen in an organic compound may be identified by warming the organic compound with aqueous silver nitrate. Which compound would form a precipitate the fastest?

Reaction kinetics

$17.6\,\text{g}$ of pentan-1-ol is fully burned. What volume of gaseous products is produced when measured at s.t.p.?

Atoms, molecules and stoichiometry

Crotyl alcohol, $\text{CH}_3\text{CH}=\text{CHCH}_2\text{OH}$, is a colourless liquid and is used as a solvent. Under suitable conditions, crotyl alcohol reacts separately with $\text{Br}_2$, $\text{K}_2\text{Cr}_2\text{O}_7/\text{H}^+$, conc. $\text{KMnO}_4/\text{H}^+$ and $\text{PCl}_5$. Which row is the correct one?

Hydroxy compounds

The displayed skeletal structures represent two organic compounds. Which reagents could be used to tell these two compounds apart?

An introduction to AS Level organic chemistry

When a carbonyl compound, $X$, is treated with HCN in the presence of NaCN, a product with $M_r = 85$ is formed. $X$ gives no reaction with Fehling’s reagent. Which compound is $X$?

Carbonyl compounds

Which compound gives butan-2-ol and ethanoic acid when it is hydrolysed?

Carboxylic acids and derivatives

Two $1\,\text{g}$ portions of $Y$ are each allowed to react fully, one with sodium and the other with sodium carbonate. The gas volumes formed are then gathered and measured. The relative gas volumes are: with $\text{Na}$: $2$ with $\text{Na}_2\text{CO}_3$: $1$ What might $Y$ be?

Atoms, molecules and stoichiometry

The diagram illustrates part of an addition polymer made from two different monomers. One monomer is propene. Identify the other monomer.

Chemical bonding

A student reacts $1\,\text{mol}$ of copper with concentrated nitric acid so that $1\,\text{mol}$ of copper(II) nitrate, $2\,\text{mol}$ of water and substance $X$ are produced. There is no additional product. Substance $X$ contains neither copper nor hydrogen. What might substance $X$ be?

Atoms, molecules and stoichiometry

A scientist selects either infrared spectroscopy or mass spectrometry in order to obtain a specific item of information. In which row has the most suitable choice been made?

Analytical techniques

In which structure are three atoms joined in a straight-line arrangement?

Chemical bonding

Which of the following statements about aluminium chloride is correct?

Chemical bonding

‘Black powder’ is a blend of potassium nitrate, carbon and sulfur. Its reaction is represented below. $4\text{KNO}_3(s) + 7\text{C}(s) + \text{S}(s) \rightarrow 3\text{CO}_2(g) + 3\text{CO}(g) + 2\text{N}_2(g) + \text{K}_2\text{S}(s) + \text{K}_2\text{CO}_3(s)$ A sealed tube with black powder has a volume of $10.0\,\text{cm}^3$. After the whole sample reacts, the process produces a pressure of $2 \times 10^6\,\text{Pa}$ and a temperature of $2500\,\text{K}$. The volume occupied by the produced $\text{K}_2\text{CO}_3$ and $\text{K}_2\text{S}$ may be neglected. What is the amount in moles of $\text{KNO}_3$ in the sealed tube?

States of matter

Which pair has the first compound boiling at a higher temperature than the second compound?

States of matter

An enthalpy change equation is presented below. The enthalpy change is $Q$. $2\text{C}(s) + 3\text{H}_2(g) + 3.5\text{O}_2(g) \xrightarrow{Q} 2\text{CO}_2(g) + 3\text{H}_2\text{O}(l)$ What expression should be used to calculate $Q$?

Chemical energetics

The four enthalpy-change equations are listed below. $ \begin{aligned} \text{Na(g)} &\rightarrow \text{Na}^+(\text{g}) + e^- && \Delta H = W \\ \text{Na(g)} &\rightarrow \text{Na}^{2+}(\text{g}) + 2e^- && \Delta H = X \\ \text{Na(s)} &\rightarrow \text{Na(g)} && \Delta H = Y \\ \text{Na(s)} &\rightarrow \text{Na}^{2+}(\text{g}) + 2e^- && \Delta H = Z \end{aligned} $ Which equation represents the second ionisation energy of sodium?

The Periodic Table: chemical periodicity

Three separate portions of $25.0\,\text{cm}^3$ of $0.1\,\text{mol dm}^{-3}\,\text{NaOH(aq)}$ are each introduced into one of three different acid solutions, as outlined. Before any mixing takes place, the temperature of each solution is $298\,\text{K}$. Which statement correctly describes the temperature increases produced when each acid is mixed separately with NaOH?

Chemical energetics

$\text{NCl}_3$ undergoes reaction with $\text{H}_2\text{O}$. $\text{NCl}_3 + 3\text{H}_2\text{O} \rightarrow \text{NH}_3 + 3\text{HClO}$ In this reaction, the oxidation state of nitrogen stays the same. Which statement is correct?

Nitrogen and sulfur

In which row do the oxidation numbers of vanadium become higher?

Electrochemistry

The methanol synthesis equation is shown below. $\text{CO}_2 + 3\text{H}_2 \rightleftharpoons \text{CH}_3\text{OH} + \text{H}_2\text{O} \qquad \Delta H = -49\,\text{kJ mol}^{-1}$ Under which conditions would the highest yield of methanol be obtained at equilibrium?

Equilibria

Hydrogen and iodine are able to react reversibly to form hydrogen iodide. The equation is given below. $\text{H}_2(\text{g}) + \text{I}_2(\text{g}) \rightleftharpoons 2\text{HI}(\text{g})$ $4.00\,\text{mol}$ of hydrogen gas and $X\,\text{mol}$ of iodine vapour are placed together in a sealed container with a volume of $1.00\,\text{dm}^3$ at $460\,\text{K}$. The mixture is then left until equilibrium is reached. At equilibrium, the mixture contains $2.00\,\text{mol}$ of hydrogen iodide. For this reaction at $460\,\text{K}$, the equilibrium constant, $K_c$, is $4.0$. Determine the value of $X$.

Equilibria

A substantial quantity of $\text{N}_2\text{O}(\text{g})$ breaks down into nitrogen gas and oxygen gas in the presence of a very small amount of gold foil catalyst. The gold foil offers a solid surface on which the catalysed reaction occurs. The graph plots the concentration of $\text{N}_2\text{O}(\text{g})$ against time while it decomposes. The graph is a straight line. Which row shows: • how the rate of reaction changes as $\text{N}_2\text{O}(\text{g})$ decomposes from $0$ to $10$ minutes • what happens to the rate of decomposition for the same amount and concentration of $\text{N}_2\text{O}(\text{g})$ if more gold foil catalyst is added?

Reaction kinetics

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

Equilibria

$\text{NH}_3(\text{aq})$ is introduced to separate samples of $\text{NaCl}(\text{aq})$, $\text{MgCl}_2(\text{aq})$, $\text{BaCl}_2(\text{aq})$ and $\text{SiCl}_4(\ell)$. In this experiment, only two of the samples give a white precipitate on addition of $\text{NH}_3(\text{aq})$. Which two samples are these?

Equilibria

What explains why the ionic radius of a sulfide ion is greater than the ionic radius of a potassium ion?

The Periodic Table: chemical periodicity

Which graph correctly displays relative electronegativity plotted against relative atomic radius for the elements Na, Mg, Al and Si?

The Periodic Table: chemical periodicity

This question concerns isolated gaseous atoms in their ground state. In which atom are all of the electrons paired?

Atomic structure

The table shows details about calcium carbonate and calcium hydroxide. Which row is correct?

Group 2

Q belongs to Group 2 metals. An excess of $\text{QCO}_3(\text{s})$ is added to $\text{H}_2\text{SO}_4(\text{aq})$, and the resulting mixture is filtered. A sample of $\text{QSO}_4$ is then collected by evaporating the filtrate. Which element could Q be?

Group 2

X, Y and Z are three elements that belong to Group 17. $\text{X}_2$ contains weaker covalent bonds than $\text{Y}_2$. The intermolecular instantaneous dipole-induced dipole forces in $\text{X}_2$ are stronger than those in $\text{Z}_2$. $\text{Y}_2$ acts as a stronger oxidising agent than $\text{Z}_2$. Which elements could X, Y and Z be?

Chemical bonding

When chlorine reacts with aqueous sodium hydroxide, two products that contain chlorine are produced. Which row gives the oxidation numbers of chlorine in those products for the conditions given?

Electrochemistry

A catalytic converter lowers the quantity of pollutants in the gases released from a car exhaust. Which row names a pollutant and indicates how it is removed by the action of the catalyst?

Reaction kinetics

A solid, R, is put into a solution of ammonium nitrate and the mixture is heated. A gas is released that changes red litmus paper to blue. What could R be?

Nitrogen and sulfur

A skeletal formula is displayed. What is the total number of stereoisomers, including the one shown?

An introduction to A Level organic chemistry

The molecular formula $\text{CH}_3$ may correspond to an anion, a cation or a free radical. A species with the molecular formula $\text{CH}_3$ can behave as an electrophile, a free radical or a nucleophile, depending on how many outer shell electrons are on the central carbon atom. How many outer shell electrons must the central carbon atom have for $\text{CH}_3$ to behave in each of these ways?

Chemical bonding

Compound Z, $\text{C}_7\text{H}_{13}\text{Br}$, contains two chiral centres. A sample of Z includes all four of the possible optical isomers. When this sample of Z is reacted with hot ethanolic NaOH, a mixture of only three isomers is formed. Two of these are optical isomers of one another. What could be the formula of Z?

Chemical bonding

In the free-radical substitution reaction of methane with chlorine, there are initiation, propagation and termination steps. Which row is correct?

Reaction kinetics

Which sample has the greatest amount of iodine?

Atoms, molecules and stoichiometry

The alkene displayed reacts with an excess of HBr by electrophilic addition. Which is the major product that is produced?

Hydrocarbons

The diagram illustrates the structures of two halogenoalkanes, P and Q. Both compounds can undergo hydrolysis. Which row is correct?

Halogen compounds

The displayed structure is that of coniine. Coniine may be prepared by allowing ammonia to react with a dibromo compound, X. $\text{NH}_3 + \text{C}_8\text{H}_{16}\text{Br}_2 \rightarrow \text{coniine} + 2\text{HBr}$ Which compound is X?

Chemical bonding

Primary alcohols may be oxidised to aldehydes by using either acidified potassium dichromate(VI) or acidified potassium manganate(VII). As the oxidising agent is reduced, the reaction mixtures undergo colour changes. What colour changes are observed?

Electrochemistry

Which reaction has a product that forms a yellow precipitate when it is treated with alkaline $\text{I}_2(aq)$?

Analytical techniques

The skeletal formula of M is shown. M is treated with an excess of LiAlH$_4$. Dilute acid is then added. What is the molecular formula of the final organic product?

Organic synthesis

Which compound gives a precipitate on mixing with 2,4-DNPH reagent and also gives a precipitate on mixing with Fehling’s reagent?

Carbonyl compounds

Which reaction can be described as a redox reaction?

Electrochemistry

Ethyl butanoate is used as a flavouring and has a fruity taste. Which row is the correct one?

Carboxylic acids and derivatives

As illustrated in the diagram, cyclohexene can undergo addition polymerisation. Which structure shows a segment of the polymer?

Chemical bonding

When a small amount of hydrocarbon Q is burned completely, it forms $3.52\,\text{g}$ of carbon dioxide and $1.44\,\text{g}$ of water. What might the structure of hydrocarbon Q be?

Atoms, molecules and stoichiometry

The following three organic compounds are given. 1. ethanal 2. propan-1-ol 3. propan-2-ol Which of these compounds would produce a mass spectrum with a fragment peak at $m/e = 43$?

Analytical techniques

Ethane and ethene are each hydrocarbon molecules. Which characteristic is shared by both molecules?

Chemical bonding

J and L are both elements in Group 15. Each of J and L forms a gaseous covalent hydride in which the oxidation number is $-3$. In the liquefied states of these hydrides, substantial hydrogen bonding is present only in the hydride of L. Which row concerning J and L could be correct?

Nitrogen and sulfur

At $150^\circ\text{C}$ and $101\,\text{kPa}$, which gas would deviate most from ideal-gas behaviour?

States of matter

An evacuated glass bulb with a volume of $200\,\text{cm}^3$ is filled with a gas at $300\,\text{K}$ and $101\,\text{kPa}$, and its mass then increases by $0.68\,\text{g}$. The gas follows the ideal gas equation. What is the identity of the gas?

States of matter

The standard enthalpy of formation of $\text{NO}_2(\text{g})$ is $+33.2\,\text{kJ mol}^{-1}$. The standard enthalpy of formation of $\text{N}_2\text{O}_4(\text{g})$ is $+9.2\,\text{kJ mol}^{-1}$. What is the standard enthalpy change for the reaction $2\text{NO}_2(\text{g}) \rightarrow \text{N}_2\text{O}_4(\text{g})$?

Chemical energetics

Which atom has precisely three unpaired electrons in its ground state?

Atomic structure

When magnesium carbonate is heated in a Bunsen burner flame, it decomposes. The values of the standard enthalpies of formation, $\Delta H_f^\circ$, for the species present are given below. $\Delta H_f^\circ\,\text{MgCO}_3 = -1095.8\,\text{kJ mol}^{-1}$ $\Delta H_f^\circ\,\text{MgO} = -601.7\,\text{kJ mol}^{-1}$ $\Delta H_f^\circ\,\text{CO}_2 = -393.5\,\text{kJ mol}^{-1}$ Calculate the standard enthalpy change for the decomposition of magnesium carbonate.

Chemical energetics

On heating, $\text{NH}_4\text{NO}_3$ decomposes to form $\text{N}_2\text{O}$ and $\text{H}_2\text{O}$. Which of the following statements are true?

Atoms, molecules and stoichiometry

A student adds $3$ mol of acidified $\text{K}_2\text{Cr}_2\text{O}_7$ to an excess of $\text{I}^-$ ions. All the chromium is reduced completely to $\text{Cr}^{3+}$, while the $\text{I}^-$ ions are oxidised to $\text{I}_2$. The $\text{I}_2$ formed is then reduced back to $\text{I}^-$ by $X$ mol of $\text{S}_2\text{O}_3^{2-}$ ions. $1$ mol of $\text{I}_2$ is reduced by $2$ mol of $\text{S}_2\text{O}_3^{2-}$ ions. What is the value of $X$?

Electrochemistry

Which statement regarding acids and bases is always true?

Equilibria

The reaction of sulfur dioxide with oxygen can proceed in both directions. $\text{2SO}_2\text{(g)} + \text{O}_2\text{(g)} \rightleftharpoons \text{2SO}_3\text{(g)}$ $K_c = 280\,\text{mol}^{-1}\,\text{dm}^3$ at $1000\,\text{K}$. For an equilibrium mixture at $1000\,\text{K}$, the sulfur trioxide concentration is $6.00\,\text{mol dm}^{-3}$. The sulfur dioxide concentration is double the oxygen concentration. What is the concentration of sulfur dioxide?

Equilibria

The particles in a mixture of gas X and gas Y have a Boltzmann distribution as shown in diagram 1. X and Y react, and this reaction leads to a greater number of gas molecules being present. The reaction proceeds to completion. For experiment 1, the rise in volume is recorded every $10\,\text{s}$. Throughout the reaction, temperature and pressure are kept constant. The volume increase is displayed on the volume-time graph in diagram 2. For experiment 2, the experiment is carried out again with the same amounts of X and Y. A different temperature is chosen from that used in experiment 1, but the same pressure is maintained. The Boltzmann distribution for the second mixture of X and Y is shown in diagram 3. During the reaction, the temperature and pressure stay constant. Which curve on the volume-time graph would represent the increase in volume against time for experiment 2? (The original line for experiment 1 is shown again as a solid line.)

Reaction kinetics

If the temperature of a particular reaction is raised by $10\,^{\circ}\text{C}$ (for example, from $20\,^{\circ}\text{C}$ to $30\,^{\circ}\text{C}$), the reaction rate roughly doubles. Which is the main explanation for this increase?

Reaction kinetics

Which ion is the smallest in radius?

The Periodic Table: chemical periodicity

Which row is the correct one?

Atoms, molecules and stoichiometry

The chlorides below are each put into water. 1 aluminium chloride 2 magnesium chloride 3 silicon tetrachloride 4 phosphorus pentachloride Which of these chlorides give an aqueous solution that reacts with sodium carbonate to release carbon dioxide?

The Periodic Table: chemical periodicity

Which element is second smallest in atomic radius within its group and second highest in electrical conductivity across its period?

The Periodic Table: chemical periodicity

$\text{NaOH(aq)}$ is introduced separately to samples of magnesium chloride solution and barium chloride solution. $\text{H}_2\text{SO}_4\text{(aq)}$ is then added drop by drop to each reaction mixture until it is in excess. What is seen at the end of this sequence of reactions?

Group 2

A sample of anhydrous Group 2 metal nitrate, Z, with mass $4.00\,\text{g}$ is heated strongly until its mass no longer changes. A solid residue of mass $1.37\,\text{g}$ is obtained. Which metal is present in Z?

Atoms, molecules and stoichiometry

Chlorine is passed as bubbles through a cylinder that holds aqueous sodium iodide and a hexane layer that does not mix with it. As the bubbles move through the cylinder, what is seen in the lower layer and in the upper layer?

Electrochemistry

Chlorine and bromine differ in volatility. Which row names the element with the greater volatility and gives the correct reason?

States of matter

Ammonium chloride dissolves easily in water. Which statement about the colourless solution that is produced is correct?

Equilibria

At $550^\circ\text{C}$, nitrogen dioxide reacts with unburnt hydrocarbon fragments such as $\text{CH}_3$ inside the catalytic converter of a motor vehicle. $4\text{CH}_3 + 7\text{NO}_2 \rightarrow 3\frac{1}{2}\text{N}_2 + 4\text{CO}_2 + 6\text{H}_2\text{O}$ Which row shows the energy change for this reaction and a reason that could explain it?

Chemical energetics

Compound X contains an alcohol group and a carbonyl group. Which row is correct?

Chemical bonding

The diagram illustrates the skeletal formula of phenazine. What is the empirical formula for phenazine?

Atoms, molecules and stoichiometry

The diagram gives the structural formula of mevalonic acid. Which reagent and conditions would react with mevalonic acid to form an organic compound that contains no chiral carbon atom?

Chemical bonding

When answering this question, both structural isomerism and stereoisomerism need to be taken into account. Y is a gaseous hydrocarbon that turns aqueous bromine colourless. $10.0\,\text{g}$ of Y occupies a volume of $3.43\,\text{dm}^3$ under room conditions. What number of isomeric structures can Y have?

Atoms, molecules and stoichiometry

An analysis of the hormone thyroxine produces the following results. When $0.500\,\text{g}$ of thyroxine is heated with aqueous silver nitrate, $0.604\,\text{g}$ of silver iodide is formed. Every atom of iodine in the thyroxine sample is converted into silver iodide. On complete combustion of $0.500\,\text{g}$ of thyroxine, $232\,\text{cm}^3$ of carbon dioxide and $7.72\,\text{cm}^3$ of nitrogen are produced, measured under room conditions. Which molecular formula of thyroxine is consistent with these values?

Atoms, molecules and stoichiometry

Limonene occurs in lemon and orange oils. What is the principal product formed when limonene reacts with an excess of dry hydrogen chloride?

Hydrocarbons

Which statement about the hydrolysis of 1-bromopropane in water is correct?

Reaction kinetics

When Compound J, $\text{C}_{15}\text{H}_{23}\text{Br}_2\text{Cl}$, is treated with an excess of hot concentrated sodium hydroxide solution in ethanol, one product formed is X. Which skeletal formula could represent X?

Halogen compounds

Only structural isomerism should be taken into account when answering this question. A number of compounds with molecular formula $\text{C}_4\text{H}_8\text{O}_2$ contain one carbonyl group and one OH group. How many of these compounds form yellow crystals with alkaline $\text{I}_2(aq)$ at room temperature?

Carbonyl compounds

Pentaerythritol is used as an intermediate in the production of paint. Which statement is correct?

Hydroxy compounds

Which reaction follows a nucleophilic addition mechanism and produces a good yield of product under the conditions given?

Carbonyl compounds

A carbonyl compound has the structural formula $\text{CH}_3\text{COCHO}$. Which row shows the correct observations when this compound is reacted with the reagents given?

Carbonyl compounds

An ester is displayed. Which two compounds combine to produce this ester?

Carboxylic acids and derivatives

Which compound can be converted into propanoic acid using a single reagent?

Carboxylic acids and derivatives

A sample of sulfur is made up mainly of $^{32}\text{S}$. It also includes $4.2\%$ $^{34}\text{S}$ and $2.8\%$ $^{36}\text{S}$. There are no further isotopes of sulfur in the sample. Calculate the relative atomic mass, $A_r$, of this sulfur sample.

Atomic structure

What number of moles of oxygen, $\text{O}_2$, are required to burn $1$ mol of ethane if the products of the reaction are water and carbon only?

Atoms, molecules and stoichiometry

A single molecule of an addition polymer with 2000 repeat units has an $M_r$ of $112000$. The polymer molecule contains chiral centres. Which monomer could be a possible precursor for this polymer?

Polymerisation

Which compound shows the least electronegativity difference between the two elements it contains?

Chemical bonding

To answer this question, use VSEPR theory. The structure of hydrazine is shown below. What value is predicted for bond angle $X$?

Chemical bonding

These questions refer to buckminsterfullerene, graphite, iodine and diamond. How many of these substances are simple molecular substances?

Chemical bonding

A student completely reacts $1$ mol of magnesium powder with oxygen in a sealed container of volume $0.030\,\text{m}^3$, where the oxygen is at a pressure of $2.0 \times 10^5\,\text{Pa}$ and a temperature of $600\,\text{K}$. The magnesium reacts completely to form $\text{MgO}$. What percentage of the oxygen is consumed?

Atoms, molecules and stoichiometry

Which equation shows the enthalpy change corresponding to the average bond energy for the C-H bond in methane?

Chemical energetics