Feb/March 2017

Which ion has an electronic configuration that is the same as $\text{Cl}^-$?

Atomic structure

The oxidation of ethanedioate ions by acidified manganate(VII) ions proceeds very slowly at room temperature. $2\text{MnO}_4^- + 5\text{C}_2\text{O}_4^{2-} + 16\text{H}^+ \rightarrow 2\text{Mn}^{2+} + 10\text{CO}_2 + 8\text{H}_2\text{O}$ $\text{Mn}^{2+}$ ions act as catalysts for this reaction. Which graph shows the way the concentration of acidified manganate(VII) ions changes after ethanedioate ions are added?

Reaction kinetics

Ammonia is produced from nitrogen and hydrogen by the Haber process. $\text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g)$ What is the expression for $K_c$ for this equilibrium?

Equilibria

The table shows the electrical conductivities of two compounds, Y and Z. - conductivity of the compound in the liquid state: Y good, Z does not conduct - conductivity of the mixture formed when the compound is added to water: Y good, Z good Which compounds could Y and Z be?

Chemical bonding

Which reagent, when combined with ammonium sulfate and then heated, gives off ammonia?

Atoms, molecules and stoichiometry

Why does barium react with cold water more quickly than magnesium?

Group 2

The values of property X for five elements from the third period of the Periodic Table, P, Q, R, S and T, are shown. P, Q, R, S and T have consecutive atomic numbers. The letters do not stand for the symbols of the elements. Which row correctly identifies property X and element R?

The Periodic Table: chemical periodicity

Several uses of chlorine and bromine are listed below. Which one is a use of bromine?

Group 17

In an experiment, $0.600\text{ mol}$ of chlorine gas, $\text{Cl}_2$, is reacted with an excess of hot aqueous sodium hydroxide. One of the products formed is $\text{NaClO}_3$. What mass of $\text{NaClO}_3$ is produced?

Atoms, molecules and stoichiometry

Z is an anhydrous compound formed from a Group 2 element. On heating, Z thermally decomposes to give two different gases. Compared with other Group 2 compounds that contain the same anion as Z, Z has a relatively low thermal stability. What is compound Z?

Group 2

Methylamine, $\text{CH}_3\text{NH}_2$, has chemical properties that are very similar to those of ammonia, $\text{NH}_3$. When methylamine reacts with hydrogen chloride, a white crystalline salt called methylammonium chloride is produced. $\text{CH}_3\text{NH}_2 + \text{HCl} \rightarrow \text{CH}_3\text{NH}_3^+\text{Cl}^-$ A sample of methylammonium chloride is warmed with aqueous sodium hydroxide. Which products are formed?

Nitrogen compounds

By mass, each of compounds J and K is $40\%$ carbon. What might J and K be?

Atoms, molecules and stoichiometry

When answering this question, take both structural isomerism and stereoisomerism into account. What is the number of isomers with the formula $\text{C}_4\text{H}_8$ whose structures include a $\pi$ bond?

Chemical bonding

Kerosene is employed as an aircraft fuel. Q is one of the molecules present in kerosene, and its skeletal formula is shown. Kerosene also contains other structural isomers of this molecule. Which structure is a structural isomer of Q?

Chemical bonding

Which radical is most likely to be produced when one covalent bond in bromochloromethane, $\text{CH}_2\text{BrCl}$, undergoes homolytic fission?

An introduction to AS Level organic chemistry

Propene can take part in several different reactions. Which row is correct?

Hydrocarbons

When ethene undergoes polymerisation, poly(ethene) is formed. How does the bonding between the carbon atoms in poly(ethene) differ from that in ethene?

Chemical bonding

Diols in which both hydroxy groups are attached to the same carbon atom can spontaneously lose a molecule of water to form a carbonyl compound. Which compound, after complete hydrolysis, gives a positive result with Tollens’ reagent?

Carbonyl compounds

Propan-2-ol takes part in many reactions. Which row is the correct one?

Hydroxy compounds

The structure of Ethane-1,2-diol is shown below. If the C-C bond is not cleaved, five oxidation products are possible. What is the combined number of aldehyde groups ($-\text{CHO}$) and carboxylic acid groups ($-\text{COOH}$) present in these five products?

Hydroxy compounds

$\text{CH}_3\text{CH}_2\text{COCH}_2\text{CH}_3$ reacts with hydrogen cyanide to produce an organic compound known as a cyanohydrin. Which statement is correct?

Carbonyl compounds

Compound X, $\text{CH}_3\text{CH(OH)CH(CHO)CH}_3$, is refluxed with an excess of acidified $\text{K}_2\text{Cr}_2\text{O}_7$ so that compound Y is produced. X and Y are then each warmed separately with Fehling’s solution and the observations recorded. What are the observations?

Carbonyl compounds

A sealed container was charged with two moles of compound P. The container was then heated, causing P to decompose partly to give only Q and R. A dynamic equilibrium involving P, Q and R was set up. When equilibrium was reached, $x$ moles of R were present, and the total number of moles present was $\left(2 + \frac{x}{2}\right)$. What equation represents this reversible reaction?

Equilibria

Which two compounds can combine to form an ester?

Carboxylic acids and derivatives

Nitrogen and phosphorus are both placed in Group 15 of the Periodic Table. Phosphorus forms a chloride with the formula $\text{PCl}_5$, but nitrogen does not form $\text{NCl}_5$. Which statements would help to account for this?

Chemical bonding

A sample of gas is compressed while its temperature is kept constant, from $1500\,\text{kPa}$ to $6000\,\text{kPa}$. Its volume decreases from $76.0\,\text{cm}^3$ to $20.5\,\text{cm}^3$. Which statements could explain this result?

States of matter

Which of the following statements are always correct?

Atoms, molecules and stoichiometry

Sulfur dioxide and oxygen undergo reaction in the gas phase. $2\text{SO}_2(g) + \text{O}_2(g) \\rightleftharpoons 2\text{SO}_3(g) \\qquad \\Delta H = -197\\,\\text{kJ mol}^{-1}$ Which of these statements are correct?

Equilibria

Test-tubes X, Y and Z each hold a small volume of water. A little $\text{NaCl}$ is then put into test-tube X. A little $\text{SiCl}_4$ is then put into test-tube Y. A little $\text{AlCl}_3$ is then put into test-tube Z. After a brief interval, two drops of Universal Indicator solution are placed into each test-tube. Which observations are seen?

Equilibria

Sodium chloride and sodium iodide are reacted with concentrated sulfuric acid. Which of these statements are correct?

Electrochemistry

Which compounds can be produced from but-2-ene in one reaction?

Hydrocarbons

Which statements can be used to explain the mechanism for the reaction of 1-chloropropane with ammonia?

Halogen compounds

Which compounds produce a pale yellow precipitate of tri-iodomethane when they react with alkaline aqueous iodine?

Carbonyl compounds

The boiling points for methane, ethane, propane and butane are listed below. $ \begin{aligned} \text{CH}_4 &: 112\,\text{K}\\ \text{CH}_3\text{CH}_3 &: 185\,\text{K}\\ \text{CH}_3\text{CH}_2\text{CH}_3 &: 231\,\text{K}\\ \text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_3 &: 273\,\text{K} \end{aligned} $ Which statement accounts for the rise in boiling point from methane to butane?

States of matter

Propanoic acid is produced naturally through bacterial fermentation of milk, and it contributes in part to the flavour of Swiss cheese. Which starting materials could be used to make propanoic acid?

Carboxylic acids and derivatives

The distinctive smell of garlic is caused by alliin. What are the approximate bond angles $x$, $y$ and $z$ in a molecule of alliin?

Chemical bonding

Which gas sample has the smallest number of molecules?

States of matter

A student combined $25.0\,\text{cm}^3$ of $4.00\,\text{mol dm}^{-3}$ hydrochloric acid with the same volume of $4.00\,\text{mol dm}^{-3}$ sodium hydroxide. At the start, both solutions were at $15.0\,^{\circ}\text{C}$. The greatest temperature measured was $30.0\,^{\circ}\text{C}$. From these measurements, determine the enthalpy change of neutralisation of hydrochloric acid?

Chemical energetics

$\text{HOCl(aq)}$ is the molecule responsible for killing bacteria when chlorine is added to water. The reaction below forms this molecule. $\text{Cl}_2(g) + \text{H}_2\text{O}(l) \rightleftharpoons \text{HOCl}(aq) + \text{H}^+(aq) + \text{Cl}^-(aq)$ Which statement about this reaction is correct?

Equilibria

Every reactant and product in an exothermic reaction is in the gaseous state. Which statement about this reaction is correct?

Equilibria

The table gives information about some of the elements in period 3.

The Periodic Table: chemical periodicity

Hydrogen halides are compounds produced when halogens (Group 17 elements) react with hydrogen. The bond polarity of the hydrogen halides decreases from HF to HI. Some relevant data are shown in the table.

Group 17

A sequence of reactions beginning with 1-bromobutane is shown.

Organic synthesis

The mass spectrum for silicon is shown. Calculate the $A_r$ of silicon. Give your answer to two decimal places.

States of matter

Complete the table with ticks ($\checkmark$) to show whether each energy change, under standard conditions, is always positive, always negative, or may be either positive or negative: electron affinity; enthalpy change of atomisation; ionisation energy; lattice energy.

Chemical energetics

Identify what $A$ to $F$ stand for.

Electrochemistry

Chlorine dioxide reacts in aqueous solution as follows: $\text{2ClO}_2 + 2\text{OH}^- \rightarrow \text{ClO}_2^- + \text{ClO}_3^- + \text{H}_2\text{O}$. The starting rate of this reaction was determined for several different initial concentrations of $\text{ClO}_2$ and $\text{OH}^-$. The results are listed in the table.

Reaction kinetics

Compound H may be prepared from benzene as illustrated.

Nitrogen compounds

Sketch the form of one $d$ orbital.

Chemistry of transition elements

Advantame is a sweetener that is about 2500 times sweeter than sucrose.

States of matter

Compounds in the root of the ginger plant give it medicinal and flavouring properties. Three of the most important compounds are gingerol, shogaol and zingerone.

Hydroxy compounds

This question concerns compound $T$, $\text{C}_x\text{H}_y\text{O}_z$. A section of the mass spectrum for $T$ is shown. The peak heights of the $M$ and $M+1$ peaks are 33.9 and 3.4 respectively.

Analytical techniques