May/June 2014

The Data Booklet is relevant for this question. Atoms of element X contain six unpaired electrons. Which element could X be?

Atomic structure

For the reaction $\text{H}_2\text{(g)} + \text{I}_2\text{(g)} \rightleftharpoons 2\text{HI(g)}$, the equilibrium constant, $K_c$, is $60$ at $450\,^\circ\text{C}$. How many moles of hydrogen iodide are present at equilibrium with $2$ mol of hydrogen and $0.3$ mol of iodine at $450\,^\circ\text{C}$?

Equilibria

Boltzmann distributions are displayed in the diagrams. For diagram 1, either curve P or Q represents the higher temperature than the other curve. For diagram 2, either line X or Y represents the activation energy when a catalyst is present, while the other line shows the activation energy for the same reaction when no catalyst is present. Which combination gives the correct curve and line?

Reaction kinetics

Redox reactions take place very often in the chemistry of Group VII. Which statement is correct?

Group 17

If equal amounts by volume of saturated barium hydroxide solution and saturated calcium hydroxide solution are combined, a white precipitate, Y, is produced. The resulting mixture is then filtered and carbon dioxide is passed through the filtrate, giving a second white precipitate, Z. What are Y and Z?

Equilibria

In what sequence do the four chlorides listed have melting points from lowest to highest? $\text{CCl}_4$, $\text{HCl}$, $\text{MgCl}_2$, $\text{PCl}_5$

States of matter

When calcium is burned in oxygen, what colour does the flame give?

Group 2

Which statement correctly describes the bonding and acid / base nature of aluminium oxide?

Chemical bonding

The thermal decomposition of Group II nitrates follows the equation below. $\text{X(NO}_3)_2 \rightarrow \text{XO} + 2\text{NO}_2 + \tfrac{1}{2}\text{O}_2$ Which Group II nitrate needs the greatest temperature for its thermal decomposition to occur?

Chemical energetics

The Data Booklet is needed for this question. A chemist used $2.00\,\text{dm}^3$ of nitrogen gas, measured under room conditions, and made it react with a large volume of hydrogen gas to produce ammonia. Only $15.0\%$ of the nitrogen gas reacted to form ammonia. What mass of ammonia was formed?

Atoms, molecules and stoichiometry

Using the Data Booklet is relevant for this question. Which graph shows relative electronegativity plotted against relative atomic radius correctly for the elements Na, Mg, Al and Si?

The Periodic Table: chemical periodicity

Use of the Data Booklet is relevant for this question. Iodine is a black, lustrous, non-metallic solid and a member of Group VII. When heated, it sublimes readily to form a purple vapour. A sample of iodine vapour with a mass of $6.35\,\text{g}$ occupies a volume of $1.247\,\text{dm}^3$ when the temperature is kept constant and the pressure is $1.00 \times 10^5\,\text{Pa}$. Assuming iodine vapour behaves as an ideal gas, what is the temperature of the iodine vapour?

States of matter

A number of organic reactions have to be warmed before they take place, although others do not need heating. Which reaction takes place rapidly at room temperature?

Reaction kinetics

Hydroxyethanal, $\text{HOCH}_2\text{CHO}$, is warmed under reflux with excess acidified potassium dichromate(VI) until oxidation no longer occurs. What is the skeletal formula of the organic product?

Electrochemistry

An ester that smells like banana has the formula $\text{CH}_3\text{CO}_2\text{CH}_2\text{CH(CH}_3)\text{CH}_2\text{CH}_3$. Which pair of reactants, under suitable conditions, would form this ester?

Carboxylic acids and derivatives

The hydrolysis of 1-chloropropane to form propan-1-ol occurs much more slowly than the equivalent hydrolysis of 1-iodopropane. Which statement accounts for this observation?

Reaction kinetics

Three structural isomers have the formula $\text{C}_5\text{H}_{12}$. Which formulae correctly show these three structural isomers?

Atoms, molecules and stoichiometry

$\text{CH}_3\text{CH}_2\text{COCH}_2\text{CH}_3$ reacts with hydrogen cyanide to give an organic product known as a cyanohydrin. Which property is true of the cyanohydrin product?

Carbonyl compounds

What number of moles of oxygen molecules is required for the complete combustion of one mole of 3-methylpent-2-ene?

Atoms, molecules and stoichiometry

The hydrocarbon $\text{C}_{17}\text{H}_{36}$ can be cracked. Which compound is least likely to form in this reaction?

Hydrocarbons

X is a compound with molecular formula $\text{C}_4\text{H}_{10}\text{O}_2$. It has a straight-chain carbon skeleton and includes two OH groups. When X reacts with an excess of hot, acidified, aqueous manganate(VII) ions, it is changed into a compound with molecular formula $\text{C}_4\text{H}_6\text{O}_4$. To which two carbon atoms in the chain of X are the two OH groups attached?

Hydroxy compounds

How many geometrical (cis-trans) isomers exist for hex-2,4-diene, $\text{CH}_3\text{CH}=\text{CHCH}=\text{CHCH}_3$?

Chemical bonding

Enthalpy changes that are not easy to measure directly can often be found by using Hess’ Law to build an enthalpy cycle. Which enthalpy change does X represent in the enthalpy cycle shown? The cycle shows $\text{C(s)} + 2\text{H}_2\text{(g)} + 2\text{O}_2\text{(g)}$ changing to $\text{CH}_4\text{(g)} + 2\text{O}_2\text{(g)}$ with $\Delta H_f^\circ$, then to $\text{CO}_2\text{(g)} + 2\text{H}_2\text{O(l)}$ with $\Delta H_f^\circ$, and reaction arrows labelled $\Delta H_c^\circ$ and X.

Chemical energetics

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. Which reagents could X and Y be?

Chemical bonding

On heating liquid $\text{N}_2\text{F}_4$, it breaks down to form only one product, X. Which statements are correct?

Equilibria

P and Q are two liquid compounds with similar $M_r$ values. The molecules in P are held together by hydrogen bonds. The molecules in Q are held together only by van der Waals’ forces. In what way do the properties of P and Q differ?

Chemical bonding

R and S combine in a reversible reaction, $\text{R} + \text{S} \rightleftharpoons \text{T}$. Which factors influence the speed of the forward reaction?

Reaction kinetics

The Brønsted-Lowry theory explains how acids and bases are identified. If concentrated sulfuric acid is combined with concentrated nitric acid, the following reactions take place. $\text{H}_2\text{SO}_4 + \text{HNO}_3 \rightleftharpoons \text{HSO}_4^- + \text{H}_2\text{NO}_3^+$ $\text{H}_2\text{NO}_3^+ \rightleftharpoons \text{H}_2\text{O} + \text{NO}_2^+$ $\text{H}_2\text{O} + \text{H}_2\text{SO}_4 \rightleftharpoons \text{HSO}_4^- + \text{H}_3\text{O}^+$ Which species function as bases in these reactions?

Equilibria

Pollutant oxide Y, which contains non-metallic element X, is produced in a car engine. In the atmosphere, Y undergoes further oxidation to Z. In this additional oxidation, $1$ mol of Y reacts with $0.5$ mol of gaseous oxygen molecules. X may be nitrogen or sulfur. Which statements about X, Y and Z could be correct?

Atoms, molecules and stoichiometry

A test-tube containing HI gas and a test-tube containing HBr gas are put together in surroundings at temperature, $T$. Which sets of observations could occur, depending on the temperature, $T$?

Equilibria

Which pair of reagents would undergo a redox reaction?

Electrochemistry

The molecule that gives the pineapple flavour in sweets has the formula $\text{CH}_3\text{CH}_2\text{CH}_2\text{CO}_2\text{CH}_2\text{CH}_3$. Which of the following statements about this molecule are correct?

Chemical bonding

The compound pentan-1,4-diol contains two OH groups in each molecule and can be oxidised. Which statements concerning pentan-1,4-diol or its oxidation products are correct?

Hydroxy compounds

The table gives the physical properties of four substances. Which substance has a giant covalent structure?

Chemical bonding

The Data Booklet is needed for this question. A product is obtained in an organic synthesis with a $62\%$ yield. Which conversions agree with this information?

Atoms, molecules and stoichiometry

A student combined $25.0\,\text{cm}^3$ of $0.350\,\text{mol dm}^{-3}$ sodium hydroxide solution with $25.0\,\text{cm}^3$ of $0.350\,\text{mol dm}^{-3}$ hydrochloric acid. The temperature increased by $2.50\,^\circ\text{C}$. Assume that none of the heat was transferred to the surroundings. The resulting mixture had a specific heat capacity of $4.20\,\text{J cm}^{-3}\,\text{K}^{-1}$. Calculate the molar enthalpy change for the reaction.

Chemical energetics

$\text{AlCl}_3$ vapour forms molecules of formula $\text{Al}_2\text{Cl}_6$ as it is cooled. How do the bond angles change during the transformation from $\text{AlCl}_3$ to $\text{Al}_2\text{Cl}_6$?

Chemical bonding

The Contact process is employed in the production of sulfuric acid. The equation for the main reaction is shown below. $2\text{SO}_2\text{(g)} + \text{O}_2\text{(g)} \rightleftharpoons 2\text{SO}_3\text{(g)} \qquad \Delta H = -196\,\text{kJ mol}^{-1}$ Which statement concerning this reaction is not correct?

Equilibria

During the manufacture of sparkler fireworks, a paste made from barium nitrate powder, aluminium powder, water and glue is spread onto wires and left to dry. At this point, the following exothermic reaction may take place. $16\text{Al} + 3\text{Ba(NO}_3)_2 + 36\text{H}_2\text{O} \rightarrow 3\text{Ba(OH)}_2 + 16\text{Al(OH)}_3 + 6\text{NH}_3$ Which conditions would be most suitable for slowing the rate of this reaction while the aluminium and barium nitrate remain unchanged?

Reaction kinetics

Which molecular arrangement will possess the smallest net dipole?

Chemical bonding

The diagram illustrates a Boltzmann distribution for the molecular energies in a gaseous mixture. The distribution has a maximum, marked $P$ on the diagram. What occurs when the temperature of the mixture rises?

Reaction kinetics

The graph shows the relative values of the first ionisation energies for four elements with consecutive atomic numbers. One of these elements reacts with hydrogen to produce a covalent compound with the formula $\text{HX}$. Which element could be $X$?

The Periodic Table: chemical periodicity

The diagram illustrates the skeletal formula of cyclopropane. The enthalpy change of formation of cyclopropane is $+53.3\,\text{kJ mol}^{-1}$, while the enthalpy change of atomisation of graphite is $+717\,\text{kJ mol}^{-1}$. The bond enthalpy of H-H is $436\,\text{kJ mol}^{-1}$ and that of C-H is $410\,\text{kJ mol}^{-1}$. What value for the mean bond enthalpy of the C-C bond in cyclopropane can be determined from these data?

Chemical energetics

What colour does the flame have when barium is burned in oxygen?

Group 2

$X$ and $Y$ are oxides of two different Period 3 elements. When one mole of $Y$ is mixed with water, the resulting solution is neutralised by exactly one mole of $X$. What might the identities of $X$ and $Y$ be?

Equilibria

Ammonium sulfate present in soil is gradually oxidised by air, with sulfuric acid, nitric acid and water formed as the only products. How many moles of oxygen gas are required to completely oxidise one mole of ammonium sulfate?

Atoms, molecules and stoichiometry

Which statement concerning the oxides and hydroxides of the Group II elements Mg, Ca, Sr and Ba is correct?

Group 2

Which graph correctly plots the relative melting points of the elements Mg, Al, Si and P against their relative electronegativities?

Chemical bonding

When solid sodium iodide is treated with concentrated sulfuric acid, the products formed are NaHSO$_4$, H$_2$S, SO$_2$ and S. During the formation of which product does sulfur’s oxidation state change by 8?

Electrochemistry

A test tube containing HBr(g) and another test tube containing HI(g) are warmed to the same temperature. Which pairing of observations could be seen?

Group 17

The Data Booklet should be used for this question. During an experiment, $0.125\,\text{mol}$ of chlorine gas, Cl$_2$, reacts with an excess of cold aqueous sodium hydroxide. One product is a compound containing sodium, oxygen, and chlorine. What mass of this product is produced?

Atoms, molecules and stoichiometry

X, Y and Z are all in the solid state. The table shows some of their physical properties. What type of lattice could each substance have?

Chemical bonding

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

Atoms, molecules and stoichiometry

Halogenoalkanes take part in a variety of nucleophilic substitution reactions. Which reaction occurs only through an S$_\text{N}1$ mechanism?

Halogen compounds

Which alcohol contains a chiral centre and can be oxidised into a ketone?

Hydroxy compounds

An ester with structural formula $\text{CH}_3\text{CO}_2\text{CH}_3$ is warmed with aqueous sodium hydroxide. What are the two organic products formed in this reaction?

Carboxylic acids and derivatives

When ethene reacts with aqueous bromine, it produces two compounds, $\text{CH}_2\text{BrCH}_2\text{Br}$ and $\text{CH}_2\text{BrCH}_2\text{OH}$. Which of the following statements about these products is correct?

Hydrocarbons

Which statement does not accurately describe a problem associated with disposing of PVC?

Polymerisation

Compound X, $\text{C}_4\text{H}_8\text{O}$, gives an orange precipitate when reacted with 2,4-dinitrophenylhydrazine reagent. When compound X is heated under reflux with acidified potassium dichromate(VI) solution, it forms a carboxylic acid. What might compound X be?

Carbonyl compounds

Dichlorodifluoromethane, $\text{CCl}_2\text{F}_2$, has been used in aerosol propellants and as a refrigerant. Which statement best explains the chemical inertness of dichlorodifluoromethane?

Chemical bonding

The diagram illustrates the structure of ethanedioic acid. Ethanedioic acid reacts with ethanol, with a few drops of concentrated sulfuric acid present, to produce a diester. The molecular formula of the diester is $\text{C}_6\text{H}_{10}\text{O}_4$. What is the structural formula of this diester?

Chemical bonding

If halogenoalkanes are heated in ethanol containing KOH, they can undergo elimination to produce alkenes. Which elimination products may be formed if 2-bromobutane is heated with KOH dissolved in ethanol?

Halogen compounds

For carbon dioxide, the enthalpy change of formation is $-394\,\text{kJ mol}^{-1}$, for water it is $-286\,\text{kJ mol}^{-1}$, and for methane it is $-74\,\text{kJ mol}^{-1}$. Calculate the enthalpy change of combustion of methane.

Chemical energetics

Artemisinin is a potent anti-malarial medicine. What number of chiral centres are present in each molecule of artemisinin?

Chemical bonding

P and Q are two compounds with closely similar $M_r$ values. In P, the molecules attract one another through hydrogen bonding. In Q, the molecules attract one another by van der Waals’ forces alone. A sample of liquid P is compared with a sample of liquid Q. In what ways will their properties be different?

Chemical bonding

Platinum catalyses the reaction $E + F \rightleftharpoons G + H$. Which of these statements about the catalyst’s properties are correct?

Reaction kinetics

Which elements have atoms that are able to form $\pi$ bonds with atoms of other elements?

Chemical bonding

Sulfuric acid counts as a Brønsted-Lowry acid. In which of these reactions is sulfuric acid acting as an acid?

Equilibria

Silver chloride dissolves in aqueous ammonia. What occurs during this process?

Equilibria

A car is fitted with a catalytic converter in its exhaust system. When the exhaust gases are analysed, they are found to contain small amounts of nitrogen oxides. Which changes would lead to lower concentrations of nitrogen oxides in the exhaust?

Equilibria

Among the alcohols listed, which ones cannot undergo dehydration to produce alkenes?

Hydroxy compounds

Menthol is a naturally occurring alcohol present in peppermint oil. Which reagents react with menthol?

Hydroxy compounds

Under suitable conditions, which reagent pairs undergo a redox reaction?

Electrochemistry

Hydrogen gas and carbon dioxide gas are present in equal molar quantities 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 $10.0\,\text{kPa}$. At $800\,\text{K}$, $K_p$ is $0.288$. Calculate the partial pressure of $\text{CO}$ in the equilibrium mixture.

Equilibria

Propanoic acid is formed naturally when milk undergoes bacterial fermentation, and it contributes partly to the characteristic taste of Swiss cheese. Which starting materials could be chosen to prepare propanoic acid?

Carboxylic acids and derivatives

On the diagram, curve $X$ was produced by monitoring the decomposition of $100\,\text{cm}^3$ of $1.0\,\text{mol dm}^{-3}$ hydrogen peroxide, with manganese(IV) oxide as the catalyst. Which change to the original experimental conditions would give curve $Y$?

Reaction kinetics

In which reaction does the species shown in bold act as an oxidising agent?

Electrochemistry

A dynamic equilibrium is reached when methane produces hydrogen and ethyne, $\text{C}_2\text{H}_2$. $2CH_4(g) \rightleftharpoons 3H_2(g) + C_2H_2(g)$ What are the units of $K_c$?

Equilibria

Which equation shows the standard enthalpy change of formation of ethanol, $\text{C}_2\text{H}_5\text{OH}$?

Chemical energetics

During an experiment, $12.0\,\text{dm}^3$ of oxygen, measured under room conditions, is used to burn completely $0.10\,\text{mol}$ of propan-1-ol. What is the final volume of gas, measured under room conditions?

Atoms, molecules and stoichiometry

The Boltzmann distribution for a gas at a constant temperature is shown below. If the gas temperature is lowered by $10^{\circ}\text{C}$, the graph alters its form. What happens to the values of $n$ for the molecular energies $X$, $Y$ and $Z$?

Reaction kinetics

$X$ is an element from Period 2. In which fluoride does the $\text{F--}X\text{--F}$ angle have the greatest value?

Chemical bonding

Which reaction corresponds to the standard enthalpy change of formation of propane?

Chemical energetics

A student studied the chloride of a Period 3 element. The compound appeared as a white crystalline solid. It dissolved readily in water to produce a solution of $\text{pH }12$. When it was put into a test-tube and heated in a roaring Bunsen flame, the compound melted after several minutes of heating. What conclusion can be drawn from these observations?

Chemical bonding

The Data Booklet is needed for this question. $X$ belongs to the $s$-block. $X$ produces an insoluble carbonate with the formula $X\text{CO}_3$. $X$ also produces a hydroxide that is more soluble than strontium hydroxide. What could be the identity of $X$?

Group 2

Use of the Data Booklet is relevant for this question. Which graph accurately displays the melting points of the elements Mg, Al, Si and P plotted against their first ionisation energies?

The Periodic Table: chemical periodicity

Which substance is not produced when hydrated magnesium nitrate undergoes thermal decomposition?

Group 2

The species Ne, $\text{Na}^+$ and $\text{Mg}^{2+}$ are isoelectronic. This indicates that they each contain the same number of electrons. In what sequence do their radii increase?

The Periodic Table: chemical periodicity

The Data Booklet may be needed for this question. In an experiment, $0.6\,\text{mol}$ of chlorine gas, $\text{Cl}_2$, is reacted with excess hot aqueous sodium hydroxide. One of the products is a compound containing sodium, oxygen and chlorine. What mass of this product is obtained?

Atoms, molecules and stoichiometry

What properties are shared by compounds of aluminium and silicon?

The Periodic Table: chemical periodicity

When strontium is burned in oxygen, what colour does the flame have?

Group 2

Which compound contains the largest overall number of lone pairs of electrons in the valence shells of all its atoms?

Chemical bonding

Diesters may be prepared from diacids such as propane-1,3-dioic acid, $\text{HO}_2\text{CCH}_2\text{CO}_2\text{H}$. Which pair of reactants would produce the diester $\text{CH}_3\text{CH}_2\text{OCOCH}_2\text{CH}_2\text{CO}_2\text{CH}_2\text{CH}_3$?

Carboxylic acids and derivatives

When ultraviolet light is present, ethane reacts with chlorine to form a mixture of products. Which compound might be found in that mixture of products?

Halogen compounds

When compound $X$ is heated under reflux with acidified potassium dichromate(VI), it forms a carboxylic acid. Compound $X$ does not react with sodium metal. What might compound $X$ be?

Carbonyl compounds

Which molecule cannot be produced by cracking one molecule of nonane, $\text{CH}_3(\text{CH}_2)_7\text{CH}_3$?

Hydrocarbons

A student carries out an investigation using four different fuels. The fuels are tested one at a time to increase the temperature of $1\ \text{dm}^3$ of water from $20\degree\text{C}$ to $100\degree\text{C}$. In every case, the fuel burns completely. All the other conditions remain unchanged for each experiment. Which fuel would give the smallest amount of carbon dioxide in these experiments?

Chemical energetics

Most alcohols may be dehydrated to form alkenes. Which alcohol may be dehydrated to form three separate isomeric alkenes?

Hydroxy compounds

Hept-4-enal occurs in cow’s milk. $\text{CH}_3\text{CH}_2\text{CH=CHCH}_2\text{CH}_2\text{CHO}$ (hept-4-enal) Which row correctly gives the product obtained when hept-4-enal is reacted with the reducing agent shown?

Carbonyl compounds

The molecule illustrated below occurs naturally and may be produced by joining four identical monomer molecules. What might the structural formula of the monomer be?

Chemical bonding

The compound cetyl palmitate, $\text{C}_{15}\text{H}_{31}\text{CO}_2\text{C}_{16}\text{H}_{33}$, is a waxy solid. When cetyl palmitate is heated under reflux with an excess of aqueous sodium hydroxide, which products are produced?

Atoms, molecules and stoichiometry

Within the Krebs cycle, one step that releases energy for the human body is the conversion of fumaric acid to malic acid. $\text{HO}_2\text{CCH=CHCO}_2\text{H} \rightarrow \text{HO}_2\text{CCH(OH)CH}_2\text{CO}_2\text{H}$ Which reagent(s) would carry out this conversion in the laboratory?

Hydroxy compounds

A reaction pathway diagram is given. For which enthalpy change would this diagram not be suitable?

Chemical energetics

The free radical substitution reaction between methane and chlorine passes through initiation, propagation and termination stages. Which row is correct?

Hydrocarbons

In 2011, a group of scientists from around the world agreed to include two further elements in the Periodic Table. Both had been produced synthetically and were named ununquadium (Uuq) and ununhexium (Uuh). Which of the following statements about these elements is correct?

The Periodic Table: chemical periodicity

P and Q are two liquid compounds whose $M_r$ values are similar. The molecules of P are held together by hydrogen bonds, whereas the molecules of Q are attracted to one another only by van der Waals’ forces. In what ways do the properties of P and Q differ?

Chemical bonding

A proportion of crude oils contain $\text{H}_2\text{S}$. In refining, the Claus process turns the $\text{H}_2\text{S}$ into solid sulfur, and this is then taken off. reaction I $2\text{H}_2\text{S}(g) + 3\text{O}_2(g) \rightarrow 2\text{H}_2\text{O}(l) + 2\text{SO}_2(g)$ reaction II $2\text{H}_2\text{S}(g) + \text{SO}_2(g) \rightarrow 2\text{H}_2\text{O}(l) + 3\text{S}(s)$ Which of the statements about the Claus process are correct?

Nitrogen and sulfur

The stoichiometry for a catalysed reaction is represented by the equation below. $\text{P}(g) + \text{Q}(g) \rightleftharpoons \text{R}(g) + \text{S}(l)$ In two experiments, the rate at which $\text{R}$ was formed was measured. The outcomes are given in the diagram below. Which changes in the conditions might explain the results shown?

Reaction kinetics

Which statements explain why sulfur dioxide is used as a food preservative?

Electrochemistry

The intermolecular attractions between iodine molecules are instantaneous dipole-induced dipole forces. Which statements account for iodine having these intermolecular forces?

Chemical bonding

Which of these reactions has to be heated in order to produce a solid product?

Equilibria

Which compounds give propanoic acid after hydrolysis with dilute sulfuric acid?

Carboxylic acids and derivatives

Propane-1,2,3-triol is the starting material for many important industrial chemical processes. Which statements about propane-1,2,3-triol are correct?

Hydroxy compounds

The Data Booklet should be used for this question. The reaction shown is the most common ion-molecule reaction found in the gas clouds of the Universe. $\text{H}_2(\text{g}) + \text{H}_2^+(\text{g}) \rightarrow \text{H}(\text{g}) + \text{H}_3^+(\text{g})$. What might the composition of an $\text{H}_3^+$ ion be?

Atoms, molecules and stoichiometry

The diagram depicts an experimental arrangement that can be used in several different experiments. Which processes could be shown using the apparatus above?

Reaction kinetics

Electrolysing brine in a diaphragm cell is an important industrial process. What occurs at the anode?

Electrochemistry

Hydrazine, $\text{N}_2\text{H}_4$, is employed as a rocket fuel since it reacts with oxygen according to the equation shown, giving gases that are considered environmentally friendly. $\text{N}_2\text{H}_4(\ell) + \text{O}_2(\text{g}) \rightarrow \text{N}_2(\text{g}) + 2\text{H}_2\text{O}(\text{g}) \quad \Delta H = -534\,\text{kJ mol}^{-1}$. Although hydrazine is used as a rocket fuel, it does not ignite spontaneously in oxygen. Which statement accounts for the fact that hydrazine does not burn spontaneously?

Reaction kinetics

A $10.0\,\text{cm}^3$ bubble of an ideal gas is produced on the sea bed, where the pressure is $2020\,\text{kPa}$. Immediately below the sea surface, the pressure is $101\,\text{kPa}$ and the temperature is the same as at the sea bed. What volume does the bubble have when it reaches just below the sea surface?

States of matter

The physical properties of four substances are shown. Which one is an ionic solid?

Chemical bonding

The enthalpy change of formation of $\text{Mn(NO}_3)_2(s)$ is $-696\,\text{kJ mol}^{-1}$. The enthalpy change of formation of $\text{MnO}_2(s)$ is $-520\,\text{kJ mol}^{-1}$. The enthalpy change of formation of $\text{NO}_2(g)$ is $+33\,\text{kJ mol}^{-1}$. When heated, $\text{Mn(NO}_3)_2$ breaks down to form $\text{MnO}_2$ and $\text{NO}_2$. $\text{Mn(NO}_3)_2(s) \rightarrow \text{MnO}_2(s) + 2\text{NO}_2(g)$. What is the standard enthalpy change for this reaction?

Chemical energetics