Feb/March 2019

A Boltzmann distribution is given for a gas sample at an initial temperature, $T_1$. The gas sample is then heated to temperature, $T_2$. Which distribution correctly represents the gas at the higher temperature, $T_2$?

Reaction kinetics

In acidic solution, potassium manganate(VII) is reacted with iron(II) ethanedioate, $\text{FeC}_2\text{O}_4$. The half-equations involved are shown below. $\text{MnO}_4^- + 8\text{H}^+ + 5\text{e}^- \rightarrow \text{Mn}^{2+} + 4\text{H}_2\text{O}$ $\text{Fe}^{2+} \rightarrow \text{Fe}^{3+} + \text{e}^-$ $\text{C}_2\text{O}_4^{2-} \rightarrow 2\text{CO}_2 + 2\text{e}^-$ How many moles of iron(II) ethanedioate are required to react with 1 mole of potassium manganate(VII)?

Electrochemistry

When copper is introduced into a silver-ion solution, the equilibrium below is set up. $\text{Cu}(s) + 2\text{Ag}^+(aq) \rightleftharpoons \text{Cu}^{2+}(aq) + 2\text{Ag}(s) \quad K_c = 1.0 \times 10^5$ What is the equilibrium concentration of silver ions when $[\text{Cu}^{2+}] = 0.10\,\text{mol dm}^{-3}$?

Equilibria

X, Y and Z are elements from Period 3 of the Periodic Table. The outcomes of several experiments performed with compounds of these elements are shown.

Chemical bonding

A solid Period 3 element, Q, is allowed to react with oxygen gas, producing compound R. If R is then added to water, the pH falls. What might the empirical formula of R be?

The Periodic Table: chemical periodicity

When metal T is reacted with water, a colourless solution forms. If this colourless solution is then mixed with aqueous sulfuric acid, a white precipitate forms. Which metal is T?

Group 2

When calcium nitrate undergoes thermal decomposition, one of the products is oxygen. What volume of oxygen is formed under room conditions when $0.50\,\text{mol}$ of calcium nitrate undergoes thermal decomposition?

Atoms, molecules and stoichiometry

L, M and N are Group 2 metals. L reacts with dilute hydrochloric acid more vigorously than N does. $\text{M(OH)}_2$ is more soluble than $\text{N(OH)}_2$. Which metals could L, M and N be?

Group 2

The table summarises some reactions of a white compound, G. When silver nitrate is added to a solution of G, and then aqueous ammonia is added, a precipitate appears and it does not dissolve after the ammonia is added. When solid G is heated with concentrated sulfuric acid, a gaseous mixture is produced that includes hydrogen sulfide. What could G be?

Group 17

At standard conditions, which statement is correct?

Chemical energetics

Ammonia, $\text{NH}_3$, and hydrazine, $\text{NH}_2\text{NH}_2$, are both nitrogen-containing compounds, $\text{N}_2$. Which of the statements is correct?

Nitrogen and sulfur

When a $3.7\,\text{g}$ sample of copper(II) carbonate is put into $25\,\text{cm}^3$ of $2.0\,\text{mol dm}^{-3}$ hydrochloric acid, what volume of gas is formed under room conditions?

Atoms, molecules and stoichiometry

How many structural isomers exist for trichloropropane, $\text{C}_3\text{H}_5\text{Cl}_3$?

Halogen compounds

Compound L has molecular formula $\text{C}_{10}\text{H}_{16}$. A sample of L was then reacted with an excess of hot, concentrated, acidified potassium manganate(VII), and compound M was formed. What might the structure of compound L be?

Hydrocarbons

A number of reactions occur in a car engine and in its catalytic converter. Which pair of substances are formed by reactions in both a car engine and a catalytic converter?

Hydrocarbons

When working through this question, you should take account of structural isomerism and stereoisomerism. 2-bromopentane is heated with an excess of ethanolic sodium hydroxide. How many different hydrocarbons are formed?

Hydrocarbons

The reaction of bromopropane with water is shown here. $\text{CH}_3\text{CH}_2\text{CH}_2\text{Br} + \text{H}_2\text{O} \rightarrow \text{CH}_3\text{CH}_2\text{CH}_2\text{OH} + \text{HBr}$ Which statement is right?

Halogen compounds

What product is obtained if 3-methylpentane-1,3,4-triol is heated under reflux in the presence of excess acidified potassium dichromate(VI)?

Electrochemistry

Menthol is an alcohol that occurs naturally. If menthol is heated with concentrated sulfuric acid, a reaction takes place. Among the products produced is compound T. Which structure could compound T have?

Hydroxy compounds

Only structural isomerism should be taken into account for this question. Each of the isomeric alcohols having molecular formula $\text{C}_5\text{H}_{12}\text{O}$ is added on its own to warm alkaline aqueous iodine. For how many of the isomers is a yellow precipitate produced?

Hydroxy compounds

On heating compound X with $\text{Cr}_2\text{O}_7^{2-}/\text{H}^+$, the solution changes from orange to green. The organic product from this reaction is then tested in two ways. Tollens’ reagent: no visible change 2,4-dinitrophenylhydrazine: orange precipitate forms What could compound X be?

Electrochemistry

1 mole of each of the following four compounds is reacted separately with: • an excess of sodium • an excess of sodium carbonate. Which compound gives the same volume of gas with both reagents?

Carboxylic acids and derivatives

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

Atomic structure

An infra-red spectrum displays a wide peak at $3000\,\text{cm}^{-1}$ and a pronounced peak at $1710\,\text{cm}^{-1}$. Which substance might have given rise to this spectrum?

Chemical bonding

In an experiment, a gaseous sample of an organic compound, J, with a volume of $10\,\text{cm}^3$ is burned in excess oxygen. The only products formed are steam, $20\,\text{cm}^3$ of carbon dioxide and $5\,\text{cm}^3$ of nitrogen. Every gas volume was taken at the same temperature and pressure. What could J be?

Atoms, molecules and stoichiometry

Which of the following pairs contain species that each have the same count of unpaired electrons in $p$ orbitals?

Atomic structure

In which of these reactions is the underlined substance reduced?

Electrochemistry

A catalytic converter is used to take away some polluting gases from car exhaust fumes. Platinum or palladium may be used as the catalyst. The reactions proceed more quickly with platinum than they do with palladium. Which statements are correct?

Reaction kinetics

Which of the following statements about ceramics are correct?

Chemical bonding

What kinds of bonding occur in ammonium carbonate, $(\text{NH}_4)_2\text{CO}_3$?

Chemical bonding

The diagram illustrates the structure of cholesterol. Which of the following statements about cholesterol are correct?

Hydroxy compounds

Chlorine atoms present in the upper atmosphere bring about the breakdown of ozone. $\text{Cl} + \text{O}_3 \rightarrow \text{O}_2 + \text{ClO}$ $\text{ClO} + \text{O} \rightarrow \text{Cl} + \text{O}_2$ Which of the following statements about these chlorine atoms are correct?

Reaction kinetics

The compounds below are treated with hydrogen cyanide. Which compounds form a molecule with a chiral centre?

Carbonyl compounds

Each of the eight species listed below contains covalent bonds. In which pair are the species shaped differently from one another?

Chemical bonding

Carboxylic acids may be prepared from alcohols, nitriles or esters. Which statements are correct?

Carboxylic acids and derivatives

Histidine is an amino acid. What are the approximate values of bond angles $1$, $2$, and $3$?

Chemical bonding

A gas sample has a volume of $240\,\text{cm}^3$ at $37\,^\circ\text{C}$ and $100\,\text{kPa}$. How many moles of gas are in the sample?

States of matter

$P$, $Q$ and $R$ are three distinct structures of an element. Which of these structures are giant molecular?

Chemical bonding

The standard enthalpy changes for combustion of carbon, hydrogen and methanol are listed below. $\text{C}(s)+\text{O}_2(g)\rightarrow\text{CO}_2(g)\quad\Delta H_c^\circ=-394\,\text{kJ mol}^{-1}$ $\text{H}_2(g)+\frac{1}{2}\text{O}_2(g)\rightarrow\text{H}_2\text{O}(l)\quad\Delta H_c^\circ=-286\,\text{kJ mol}^{-1}$ $\text{CH}_3\text{OH}(l)+\frac{3}{2}\text{O}_2(g)\rightarrow\text{CO}_2(g)+2\text{H}_2\text{O}(l)\quad\Delta H_c^\circ=-726\,\text{kJ mol}^{-1}$ Which expression represents the standard enthalpy change of formation of methanol, in $\text{kJ mol}^{-1}$?

Chemical energetics

A chemical reaction equation is given below. Every substance is in its standard state. $\text{XeF}_6 + 3\text{H}_2\text{O} \rightarrow \text{XeO}_3 + 6\text{HF}$ Which statement gives the standard enthalpy change of reaction for this reaction?

Chemical energetics

Nitrogen, $\text{N}_2$, is the most plentiful gas in the Earth’s atmosphere and is highly unreactive.

Nitrogen and sulfur

The elements in Group 17 of the Periodic Table are known as the halogens. They form stable compounds with metals and with non-metals. The table provides some data for $\text{F}_2$, $\text{HCl}$ and $\text{CaF}_2$.

Atoms, molecules and stoichiometry

P, Q and R each have five carbon atoms. A student performs a number of tests to tell P, Q and R apart.

Carbonyl compounds

Allyl chloride is a significant chemical employed in making plastics, pharmaceuticals and pesticides.

Atoms, molecules and stoichiometry

State one natural source and one man-made source of oxides of nitrogen.

Chemical energetics

The table below gives the solubilities of the hydroxides and carbonates of several Group 2 elements, M, at $25\,^{\circ}\text{C}$.

Group 2

Give mathematical expressions for the following terms: pH; $K_a$ for a weak acid, $\text{HA}$.

Equilibria

Complete the electronic configuration for a copper atom. $$1s^22s^22p^6\ \ldots$$

Chemistry of transition elements

Methyl 2-cyanoprop-2-enoate, $W$, is the principal ingredient in Super Glue, a fast-setting adhesive. When the adhesive hardens, monomer $W$ undergoes polymerisation.

States of matter

Many drugs used in medicine often have names that contain fragments taken from the functional groups present in their molecules.

Analytical techniques

Ethanedioyl dichloride, $\text{ClCOCOCl}$, is a valuable reagent in organic synthesis. It can be prepared from compound A in one step.

States of matter