May/June 2017

Which molecule has six bonding electrons?

Chemical bonding

Methanol may be made from hydrogen and carbon monoxide. $2\text{H}_2(g) + \text{CO}(g) \rightleftharpoons \text{CH}_3\text{OH}(g)$. What is the $K_p$ expression for this reaction?

Equilibria

After $4\,\text{g}$ of powdered calcium carbonate, $M_r = 100$, was added to $100\,\text{cm}^3$ of $0.10\,\text{mol dm}^{-3}$ hydrochloric acid, the volume of carbon dioxide formed was measured. Which row contains the correct explanations for these observations?

Atoms, molecules and stoichiometry

Explain why the second ionisation energy of sodium is greater than the second ionisation energy of magnesium.

The Periodic Table: chemical periodicity

Which graph shows correctly how the relative melting points of the elements Mg, Al, Si and P are plotted against their relative electronegativities?

Chemical bonding

An excess of MgO is shaken with water. The mixture formed is then filtered into test-tube X. An excess of BaO is shaken with water. The mixture formed is then filtered into test-tube Y. Which oxide reacts more easily with water, and which filtrate has the lower pH?

Group 2

Samples of magnesium carbonate, $\text{MgCO}_3$, are put into crucibles R and S. The material in crucible R is heated until its mass no longer decreases, then it is left to cool. The material in crucible S is not heated. Dilute hydrochloric acid is then added to both crucibles. After the dilute hydrochloric acid is added, which observations are correct?

Group 2

Which statement concerning nitrogen or one of its compounds is correct?

Nitrogen and sulfur

If concentrated sulfuric acid is allowed to react with sodium iodide, the products formed include sulfur, iodine, hydrogen sulfide and sulfur dioxide. Which statement is correct?

Electrochemistry

Under specific conditions, a solution of sodium hydroxide reacts with $3\text{ mol}$ of chlorine. From the reaction, $5\text{ mol}$ of sodium chloride and $1\text{ mol}$ of X are formed; X is the only other product that contains chlorine. What formula does compound X have?

Atoms, molecules and stoichiometry

Redox reactions occur frequently in Group 17 chemistry. Which statement is correct?

Electrochemistry

A mass spectrum for a lithium sample indicates the presence of two isotopes, $^6\text{Li}$ and $^7\text{Li}$. The isotopic abundances are given in the table: $^6\text{Li}$ = $7.42\%$, $^7\text{Li}$ = $92.58\%$. What is the relative atomic mass of this lithium sample, to three significant figures?

Atoms, molecules and stoichiometry

You should take both structural isomerism and stereoisomerism into account when answering this question. Each carbonyl compound below is treated with $\text{NaBH}_4$. The product from each reaction is then heated with $\text{Al}_2\text{O}_3$ at $600^\circ\text{C}$, forming either a single product or a mixture of isomers. Which carbonyl compound would give the greatest number of isomers?

Carbonyl compounds

The formula for the drug cortisone is shown. Apart from the chiral centres indicated by an asterisk (*), how many additional chiral centres are found in the cortisone molecule?

Chemical bonding

An alkene is treated with acidified manganate(VII) ions, $\text{MnO}_4^-$. The required organic product has a relative molecular mass that is $34$ higher than that of the alkene. What conditions should be used?

Hydrocarbons

The diagram represents a small section of an addition polymer chain. This polymer has a relative molecular mass of about $10000$. About how many monomer units are linked together in each polymer molecule?

Atoms, molecules and stoichiometry

Lactide is an intermediate used in the production of a synthetic fibre. Which compound can form lactide when heated with an acid catalyst?

Carboxylic acids and derivatives

Diols in which both hydroxy groups are attached to the same carbon atom readily lose a molecule of water to form a carbonyl compound. Which compound is hydrolysed to give a product that gives a positive reaction with 2,4-dinitrophenylhydrazine but not with Fehling’s reagent?

Carbonyl compounds

X and Y are the reagents needed to change 1-bromopropane into butanoic acid. Which substances are X and Y?

Organic synthesis

Q is a compound with the molecular formula $\text{C}_4\text{H}_{10}\text{O}$. Q may be oxidised using acidified potassium dichromate(VI). Q cannot be obtained by reducing a carboxylic acid with $\text{LiAlH}_4$. Identify the structure of Q.

Hydroxy compounds

A $2.30\,\text{g}$ sample of ethanol was combined with an excess of aqueous acidified potassium dichromate(VI). The reaction mixture was then heated under reflux for one hour. The desired organic product was afterwards obtained by distillation. The yield of product was $60.0\%$. Calculate the mass of product obtained.

Atoms, molecules and stoichiometry

Which compound produces a positive result with alkaline aqueous iodine and does not exhibit optical isomerism?

Analytical techniques

A sports medal has a total surface area of $150\,\text{cm}^2$. It was coated uniformly with silver by electrolysis. Its mass rose by $0.216\,\text{g}$. How many silver atoms were deposited on each $\text{cm}^2$ of the medal's surface?

Atoms, molecules and stoichiometry

Citral is present in lemongrass oil. It may react to form compound W. Citral $\xrightarrow[\text{an excess of }\text{H}_2/\text{Ni}]{}$ V $\xrightarrow[\text{hot, concentrated acidified manganate(VII) under reflux}]{}$ W What might compound W be?

Carboxylic acids and derivatives

A beam of charged particles is bent by an electric field. When the conditions are the same, the angle through which a particle is deflected is proportional to its charge/mass ratio. In one experiment, protons are deflected through an angle of $+15^{\circ}$. In a second experiment under the same conditions, particle Y is deflected through an angle of $-5^{\circ}$. What could particle Y consist of?

Atomic structure

Graphene, graphite and the fullerene $\text{C}_{60}$ are allotropes of carbon. Which of the following statements are true for all three of these carbon allotropes?

Chemical bonding

The reaction between carbon and oxygen is given. $\text{C(s)} + \frac{1}{2}\,\text{O}_2(\text{g}) \rightarrow \text{CO(g)}$ Which description best matches the enthalpy change for this reaction?

Chemical energetics

Which changes may be used to measure the rates of chemical reactions?

Reaction kinetics

Which statements describe a trend in Period 3 for each neighbouring pair of elements from sodium through to chlorine?

The Periodic Table: chemical periodicity

X is either nitrogen or sulfur, and in a car engine it forms the pollutant oxide Y. Y is then further oxidised to Z in the atmosphere. During this additional oxidation, $1\,\text{mol}$ of Y reacts with $0.5\,\text{mol}$ of gaseous oxygen molecules. Which of the following statements about X, Y and Z could be correct?

Atoms, molecules and stoichiometry

P and Q form a pair of cis-trans isomers. Which feature must be identical for P and Q?

Chemical bonding

The reaction of NaOH(aq) with the three chloroalkanes shown is considered below. $\text{CH}_3\text{CH}_2\text{CHClCH}_3$ \quad $(\text{CH}_3)_2\text{CHCH}_2\text{Cl}$ \quad $(\text{CH}_3)_3\text{CCl}$ Which of these statements are correct?

Halogen compounds

Which reactions have the colour changes stated accurately?

Group 17

Which property of an atom has no influence on its first ionisation energy?

The Periodic Table: chemical periodicity

Which of these statements about ethanol and ethanoic acid are correct?

Carboxylic acids and derivatives

Which molecule shows the greatest overall dipole?

Chemical bonding

When $2$ moles of a straight chain alkane undergo complete combustion, $400\,\text{dm}^3$ of carbon dioxide are produced, with the gas volume taken at $301\,\text{K}$ and $1 \times 10^5\,\text{Pa}$. It may be assumed that carbon dioxide behaves ideally under these conditions. Determine the formula of the straight chain alkane.

Atoms, molecules and stoichiometry

Which expression represents the standard enthalpy change of combustion of methane?

Chemical energetics

Household bleaches and disinfectants often contain solutions with chlorate(I) ions. When these solutions are heated, they decompose as shown: $3\text{ClO}^- \rightarrow \text{ClO}_3^- + 2\text{Cl}^-$. Which oxidation state is shown by chlorine in each of these three ions?

Electrochemistry

When $\text{K}_2\text{MnO}_4$ is added to water, this reaction takes place: $a\,\text{MnO}_4^{2-}(aq) + b\,\text{H}_2\text{O}(l) \rightarrow c\,\text{MnO}_4^{-}(aq) + d\,\text{MnO}_2(s) + e\,\text{OH}^-(aq)$. What are the values of $a$ and $c$ in the balanced chemical equation?

Electrochemistry

For which species are the numbers of protons, neutrons and electrons all different?

Atomic structure

The reaction below is part of the Contact process. $2\text{SO}_2(g) + \text{O}_2(g) \rightleftharpoons 2\text{SO}_3(g) \quad \Delta H^\circ = -197\,\text{kJ mol}^{-1}$ This reaction is studied at $200\,\text{kPa}$ and $700\,\text{K}$, and the equilibrium constant, $K_p$, is determined to be $Y$. It is then studied again at $1000\,\text{kPa}$ and $700\,\text{K}$, and the value of $K_p$ is found to be $Z$. Which statement about the comparison between $Y$ and $Z$ is correct?

Equilibria

The Boltzmann distribution for the hydrogenation of an alkene at a specific temperature without a catalyst is shown. Which row correctly describes what happens when nickel is added to the reaction vessel?

Reaction kinetics

Magnesium and sulfur each produce ions with a 2+ charge. How do the atomic radii and ionic radii of these two elements compare?

The Periodic Table: chemical periodicity

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

The Periodic Table: chemical periodicity

Patterns can be observed in the physical and chemical properties of the elements in Group 2 and in their compounds. Which property decreases from magnesium to barium?

Group 2

Calcium oxide is mixed with water, and the mixture is then filtered. The liquid that passes through is filtrate X. If carbon dioxide is bubbled through filtrate X, a white precipitate appears. Which equation correctly represents the reaction between filtrate X and carbon dioxide?

Group 2

When element X is treated with cold, dilute, aqueous sodium hydroxide, two distinct chlorine-containing products, Y and Z, are produced. What are the oxidation states of chlorine in Y and Z?

Electrochemistry

The powder is known to be either a single sodium halide or a blend of two sodium halides. A portion of the powder was dissolved in water. Aqueous silver nitrate was added, and a pale yellow precipitate appeared. When concentrated aqueous ammonia was then added, part of this precipitate dissolved, leaving behind a darker yellow precipitate. What could the powder be?

Group 17

The ammonium ion is produced by the reaction shown below. $\text{NH}_3 + \text{H}^+ \rightarrow \text{NH}_4^+$ Which of the following statements about the species taking part in this reaction is correct?

Chemical bonding

A chemist used $2.00\,\text{dm}^3$ of nitrogen gas, measured at room conditions, and allowed it to react with an excess volume of hydrogen gas to make ammonia. Only $15.0\%$ of the nitrogen gas went on to react to form ammonia. What mass of ammonia was produced?

Atoms, molecules and stoichiometry

Which option would include $9.03 \times 10^{23}$ oxygen atoms?

Atoms, molecules and stoichiometry

A carbonyl compound X reacts with HCN in the presence of NaCN to produce a compound with $M_r = 85$. Compound X does not react with Fehling’s reagent. Identify X.

Carbonyl compounds

Geraniol and linalool are compounds present in certain flower fragrances. Which statement is correct?

Hydroxy compounds

Which equation shows the initiation step in the substitution reaction of methane with chlorine?

Halogen compounds

When aqueous sodium hydroxide reacts with 1-bromopropane to form propan-1-ol, what needs to be shown in a diagram for the first step in the mechanism?

Halogen compounds

A $2.76\,\text{g}$ sample of ethanol was combined with excess aqueous acidified potassium dichromate(VI). The reaction mixture was then heated under reflux for one hour. The organic product needed was afterwards obtained by distillation. The product yield was $75.0\%$. What mass of product was collected?

Atoms, molecules and stoichiometry

Compound X is a single, pure optical isomer. When X is heated with an excess of concentrated $\text{H}_2\text{SO}_4$, only one organic product is produced. What could X be?

Hydroxy compounds

When heated under reflux with an aqueous solution of sodium hydroxide, 2-bromo-2-methylpropane undergoes nucleophilic substitution. Which row is correct?

Halogen compounds

$\text{H}_2\text{NNHC}_6\text{H}_3(\text{NO}_2)_2$ gives the structural formula of 2,4-DNPH. A large number of organic reactions, though not all, have to be heated before they take place. Which reaction proceeds at a satisfactory rate at room temperature ($20\,^{\circ}\text{C}$)?

Reaction kinetics

A carboxylic acid, P, cannot form any chain isomers. It reacts with an alcohol, Q, which has only one positional isomer. What ester could be produced by a reaction between P and Q?

Carboxylic acids and derivatives

Which compound is chiral and reacts with $\text{Na}_2\text{CO}_3$ to produce $\text{CO}_2$?

Carboxylic acids and derivatives

In some fireworks, powdered aluminium reacts with powdered barium nitrate. Heat is released, an unreactive gas is formed, and every nitrogen atom is reduced. What is the equation for this reaction?

Nitrogen and sulfur

When hydrolysed, which compound produces propanoic acid together with propan-2-ol?

Carboxylic acids and derivatives

For a single gaseous atom of element X, at least one of the $3d$ orbitals contains a pair of electrons, and the $4s$ subshell is full. What is the possible identity of element X?

Atomic structure

Which carbon allotropes possess a giant molecular structure?

Chemical bonding

Which of the following statements concerning endothermic reactions are correct?

Chemical energetics

The rate of a chemical reaction can be increased by adding a suitable catalyst. Which of these reactions can make use of a heterogeneous catalyst? 1 $\text{N}_2 + 3\text{H}_2 \rightleftharpoons 2\text{NH}_3$ 2 $2\text{SO}_2 + \text{O}_2 \rightleftharpoons 2\text{SO}_3$ 3 $2\text{NO} + 2\text{CO} \rightleftharpoons \text{N}_2 + 2\text{CO}_2$

Reaction kinetics

Which chlorides, if placed in water, can form a solution with pH below $5$? 1 $\text{SiCl}_4$ 2 $\text{AlCl}_3$ 3 $\text{MgCl}_2$

Equilibria

Acid rain remains an environmental issue. Which of the following statements about acid rain are correct? 1 Acid rain is produced when oxides of nitrogen or oxides of sulfur react with water in the atmosphere. 2 Acid rain leads to a rise in the concentration of heavy metal ions in water courses. 3 Nitrogen dioxide will catalyse the formation of $\text{SO}_3$ from $\text{SO}_2$ in the atmosphere.

Nitrogen and sulfur

Among the compounds below, which one contains a chiral centre? 1 2-hydroxybutanoic acid 2 3-hydroxybutanoic acid 3 4-hydroxybutanoic acid

Chemical bonding

The diagram illustrates the monomer from which polyvinyl chloride, PVC, is made. If one particular polymer molecule is formed from $n$ monomer molecules (where $n$ is many thousands), which of the following statements are true? 1 The relative molecular mass of this polymer molecule is about $62.5n$. 2 This polymer molecule contains $n$ chiral carbon atoms. 3 A single polymer molecule has $5n$ $\sigma$ bonds.

Chemical bonding

An organic compound, $X$, has the skeletal formula shown below. Which of the following statements about $X$ are correct? 1 $X$ is a primary alcohol. 2 $X$ will dehydrate to produce a single alkene. 3 $X$ will take part in a substitution reaction with chloride ions.

Chemical bonding

Which organic compound has the greatest boiling point?

States of matter

2,2,4-trimethylpentanal is employed in the production of adhesives. With which reagents would 2,2,4-trimethylpentanal react? 1 2,4-dinitrophenylhydrazine reagent 2 Tollens' reagent 3 alkaline aqueous iodine

Carbonyl compounds

For a sample of $0.321\,\text{g}$ of sulfur vapour, the volume is $2.08 \times 10^6\,\text{m}^3$ at $2500\,\text{K}$ and a pressure of $1.00 \times 10^{-4}\,\text{Pa}$. What molecular formula does sulfur have under these conditions?

Atoms, molecules and stoichiometry

Which reaction results in a reduction in the bond angle at a carbon atom?

Chemical bonding

At the elevated temperatures found in car engines, nitrogen reacts with oxygen to produce nitrogen monoxide. $\tfrac{1}{2}\text{N}_2(g) + \tfrac{1}{2}\text{O}_2(g) \rightarrow \text{NO}(g) \quad \Delta H^\circ = +90\,\text{kJ mol}^{-1}$ This reaction has activation energy $E_a$. Which reaction pathway diagram could show this reaction correctly?

Reaction kinetics

A reaction pathway is illustrated. $\text{SO}_2 \xrightarrow{1} \text{SO}_3 \xrightarrow{2} \text{H}_2\text{SO}_4 \xrightarrow{3} \text{H}_2\text{S} \xrightarrow{4} \text{SO}_2$ At each step in this pathway, sulfur is oxidised, reduced, or neither oxidised nor reduced. Which row is correct?

Electrochemistry

Hydrogen gas and carbon dioxide gas are combined at $800\,\text{K}$. A reversible reaction occurs. $\text{H}_2(g) + \text{CO}_2(g) \rightleftharpoons \text{H}_2\text{O}(g) + \text{CO}(g)$ When equilibrium is reached, the partial pressures of $\text{H}_2$ and $\text{CO}_2$ are each $10.0\,\text{kPa}$. The value of $K_p$ at $800\,\text{K}$ is $0.288$. What is the partial pressure of $\text{CO}$ in the equilibrium mixture?

Equilibria

The ion $\text{Y}^{3-}$ has 18 electrons and a mass number of 31. How many protons and neutrons are present in $\text{Y}^{3-}$?

Atomic structure

For the equation shown, an equilibrium is reached at a temperature of $700\,\text{K}$. The equilibrium constant, $K_p$, for this reaction is $9.80\,\text{kPa}$. At equilibrium, the partial pressure of $\text{N}_2\text{O}_4$ is $80.0\,\text{kPa}$. $\text{N}_2\text{O}_4\text{(g)} \rightleftharpoons 2\text{NO}_2\text{(g)}$ What is the partial pressure of $\text{NO}_2$ at equilibrium?

Equilibria

The diagram illustrates the Boltzmann distribution for the energy of gaseous molecules at a given temperature. Which statement is correct?

Reaction kinetics

Magnesium chloride, $\text{MgCl}_2$, and silicon tetrachloride, $\text{SiCl}_4$, are each placed into water separately. What approximate pH values do the resulting solutions have?

The Periodic Table: chemical periodicity

Which graph accurately displays the relative melting points of the elements Mg, Al, Si and P when plotted against their relative first ionisation energies?

The Periodic Table: chemical periodicity

The table provides information about calcium carbonate and calcium hydroxide. Which row is correct?

Group 2

Which row gives the correct description of how calcium and strontium react with water?

Group 2

When chlorine gas is introduced into cold aqueous sodium hydroxide, one reaction occurs. In a different experiment, chlorine gas is introduced into hot aqueous sodium hydroxide. Which oxidation states of chlorine appear in the reactants and products for the two reactions that occur?

Electrochemistry

A test-tube containing $\text{HBr(g)}$ and another separate test-tube containing $\text{HI(g)}$ are heated until both reach the same temperature. Which set of observations could be seen?

Halogen compounds

Ammonia is made up of simple covalent molecules, $\text{NH}_3$. It may react with suitable reagents to produce substances that contain ammonium ions, $\text{NH}_4^+$. It can also react with suitable reagents to produce substances that contain amide ions, $\text{NH}_2^-$. Which of these nitrogen-containing species are found in an aqueous solution of ammonia?

Equilibria

What substance would be formed when $60\,\text{g}$ of nitrogen monoxide reacts with an excess of carbon monoxide in a catalytic converter?

Atoms, molecules and stoichiometry

When a $0.216\,\text{g}$ sample of an aluminium compound $X$ is reacted with water present in excess, one hydrocarbon gas is produced. That gas undergoes complete combustion in $\text{O}_2$, giving only $\text{H}_2\text{O}$ and $\text{CO}_2$. The volume of $\text{CO}_2$ measured at room temperature and pressure is $108\,\text{cm}^3$. What formula does $X$ have?

Atoms, molecules and stoichiometry

Structural isomerism and stereoisomerism must be taken into account when answering this question. Which formula identifies only one substance?

An introduction to AS Level organic chemistry

Both structural isomerism and stereoisomerism need to be taken into account when you answer this question. When a molecule has two non-identical chiral carbon atoms, there are four optical isomers. What is the number of isomers with molecular formula $\text{C}_7\text{H}_{14}\text{O}$, a five-membered ring and a tertiary alcohol group?

Atoms, molecules and stoichiometry

The formulae for three compounds are given: $\text{C}_3\text{H}_7\text{CHO}$, $\text{C}_2\text{H}_5\text{COCH}_3$ and $\text{CH}_2\text{CHCH}_2\text{CH}_2\text{OH}$. Of these compounds, only one will decolourise bromine water. Of these compounds, only one will produce a silver mirror with Tollens’ reagent. Which row gives the correct outcomes?

Carbonyl compounds

Carboxylic acids can be made by a number of different routes. In which reaction would propanoic acid be produced?

Carboxylic acids and derivatives

The diagram shows the arrangement of a polymer. By what method could this polymer be produced?

Chemical bonding

In the dark, bromine reacts with ethene. Which statement correctly describes the organic intermediate formed in this reaction?

Hydrocarbons

Which statement concerning butan-1-ol, butan-2-ol, and 2-methylbutan-2-ol is incorrect?

Hydroxy compounds

Which compound reacts with acidified potassium dichromate(VI) and with alkaline aqueous iodine?

Hydroxy compounds

Chlorogenic acid occurs in green coffee beans and is used in weight-loss treatments. Which product is obtained in good yield when chlorogenic acid is reacted with an excess of sodium carbonate solution at room temperature? ($R = \text{C}_5\text{H}_9\text{O}_2$ and does not take part in the reaction with sodium carbonate.)

Carboxylic acids and derivatives

Butanoic acid may be made from 1-bromopropane by using reagents X and Y, as illustrated: 1-bromopropane $\xrightarrow{\text{reagent X}}$ compound Q $\xrightarrow{\text{reagent Y}}$ butanoic acid. What could be reagents X and Y?

Atoms, molecules and stoichiometry

Which equation shows the complete combustion of an alkene, $\text{C}_n\text{H}_{2n}$?

Atoms, molecules and stoichiometry

How many esters having the molecular formula $\text{C}_5\text{H}_{10}\text{O}_2$ can be prepared by reacting a primary alcohol with a carboxylic acid?

Carboxylic acids and derivatives

Which statements concerning the atoms $^{23}_{11}\text{Na}$ and $^{24}_{12}\text{Mg}$ are correct?

Atomic structure

Which of the following compounds have covalent bonds?

Chemical bonding

Ethylene glycol, $\text{HOCH}_2\text{CH}_2\text{OH}$, is used as a de-icer. It enables ice to melt at temperatures below $0\,^\circ\text{C}$. Which statements are correct?

States of matter

A student performed two experiments in which $\text{MnO}_2$ acted as a catalyst to break down hydrogen peroxide. The equation for this reaction is shown. $2\text{H}_2\text{O}_2\text{(aq)} \rightarrow 2\text{H}_2\text{O(l)} + \text{O}_2\text{(g)}$. Which statements are correct?

Reaction kinetics

A solid magnesium compound has the formula $\text{Mg(NO}_3)_2\cdot 6\text{H}_2\text{O}$. If this solid is heated in a hard-glass test-tube, one or more changes may be seen. Which statements are correct?

Group 2

Sulfur dioxide is a pollutant in the atmosphere. What could happen if sulfur dioxide gas were released into the atmosphere?

Nitrogen and sulfur

Which reaction mechanisms are shown by this sequence of reactions? $\text{CH}_3\text{CH}_2\text{CH}_3 \rightarrow \text{CH}_3\text{CH}_2\text{CH}_2\text{Cl} \rightarrow \text{CH}_3\text{CH}_2\text{CH}_2\text{OH} \rightarrow \text{CH}_3\text{CHCH}_2 \rightarrow \text{CH}_3\text{CHBrCH}_2\text{Br}$

Chemical bonding

Which compounds, when heated in ethanolic NaOH, yield more than one product with molecular formula $\text{C}_4\text{H}_8$?

Halogen compounds

Substance M is heated under reflux with aqueous sodium hydroxide. One of the products formed in this reaction gives a pale yellow precipitate when it reacts with alkaline aqueous iodine. Which compounds could be substance M?

Carbonyl compounds

The two conversions below are shown. $\text{NH}_4^+ \rightarrow \text{NH}_3$ $\text{C}_2\text{H}_4 \rightarrow \text{C}_2\text{H}_6$ What common feature do these two conversions share?

Atomic structure

Propanal reacts with hydrogen cyanide to produce 2-hydroxybutanenitrile. Sodium cyanide is a suitable catalyst for this reaction. $\text{CH}_3\text{CH}_2\text{CHO} + \text{HCN} \xrightleftharpoons[\text{ }]{\text{NaCN}} \text{CH}_3\text{CH}_2\text{CH(OH)CN}$. Which of the statements below about propanal reacting with hydrogen cyanide are correct?

Carbonyl compounds

All of the gases named are under the same pressure. Which gas is expected to behave most nearly as an ideal gas?

States of matter

Use the data below for this question. $\Delta H_f^\circ(\text{CO(g)}) = -111\,\text{kJ mol}^{-1}$ $\Delta H_f^\circ(\text{CO}_2\text{(g)}) = -394\,\text{kJ mol}^{-1}$ $\Delta H_f^\circ(\text{Fe}_2\text{O}_3\text{(s)}) = -822\,\text{kJ mol}^{-1}$ Iron(III) oxide reacts with carbon monoxide. $3\text{CO(g)} + \text{Fe}_2\text{O}_3\text{(s)} \rightarrow 3\text{CO}_2\text{(g)} + 2\text{Fe(s)}$ Calculate the enthalpy change when $55.8\,\text{g}$ of iron are produced by this reaction?

Chemical energetics

Vanadium reacts with dilute sulfuric acid and produces $\text{V}_2(\text{SO}_4)_3$ plus hydrogen gas. What change do vanadium atoms undergo in this reaction?

Electrochemistry

$\text{Na}_2\text{S}_2\text{O}_3$ reacts with $\text{HCl}$ as shown. $\text{Na}_2\text{S}_2\text{O}_3\text{(aq)} + 2\text{HCl(aq)} \rightarrow 2\text{NaCl(aq)} + \text{H}_2\text{O(l)} + \text{SO}_2\text{(g)} + \text{S(s)}$ To determine the oxidation number of sulfur in $\text{Na}_2\text{S}_2\text{O}_3$, the mean oxidation number for the two sulfur atoms should be used. State the oxidation number of sulfur in each of $\text{Na}_2\text{S}_2\text{O}_3$, $\text{SO}_2$, and $\text{S}$?

Electrochemistry

Ammonia is made by using the Haber process. $\text{N}_2 + 3\text{H}_2 \rightleftharpoons 2\text{NH}_3 \qquad \Delta H^\circ = -92\,\text{kJ mol}^{-1}$ A problem with the temperature control in the process caused the temperature to rise to $600^\circ\text{C}$ for two hours. How did this affect ammonia production during this period?

Equilibria