Feb/March 2020

How many protons, neutrons and electrons are there in the ion $^{54}_{26}\text{Fe}^{3+}$?

Atomic structure

After the equation has been balanced correctly, what is the value of $c$? $a\text{C}_2\text{H}_4 + b\text{H}_2\text{O} + c\text{H}^+ + 2\text{MnO}_4^- \rightarrow d\text{C}_2\text{H}_6\text{O}_2 + e\text{Mn}^{2+}$

Electrochemistry

A key stage in the Contact process involves an equilibrium reaction. $2\text{SO}_2 + \text{O}_2 \rightleftharpoons 2\text{SO}_3$ Which row shows the effect of the named condition on the equilibrium yield?

Equilibria

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

Equilibria

Compound Z does not dissolve in water, but it does dissolve at low pH. What might compound Z be?

Equilibria

Aqueous sodium hydroxide, when heated, reacts with chlorine. $6\text{NaOH(aq)} + 3\text{Cl}_2(g) \rightarrow 5\text{NaCl(aq)} + \text{NaClO}_3(aq) + 3\text{H}_2\text{O(l)}$ Which statement is correct?

Electrochemistry

Solid ammonium nitrate is placed in a test-tube and solution X is added to it. The mixture formed is then warmed, and the gas released is tested using damp red litmus paper. The litmus paper changes colour from red to blue. What could be the identity of X and its role in the reaction?

Nitrogen and sulfur

Sodium, magnesium and aluminium are three elements in Period 3 of the Periodic Table. Each one forms an oxide. Which row is correct?

Atoms, molecules and stoichiometry

A student heats calcium nitrate crystals using the apparatus illustrated. A colourless gas escapes from the apparatus at Y. A flame is brought to this gas. Which observations would the student make?

Nitrogen and sulfur

What occurs when concentrated sulfuric acid reacts with sodium chloride?

Atoms, molecules and stoichiometry

Which of the following statements about nitrogen or its compounds is correct?

Nitrogen and sulfur

For which hydrocarbon are the molecular formula and empirical formula identical?

Atoms, molecules and stoichiometry

Which two compounds are a pair of functional group isomers?

An introduction to AS Level organic chemistry

Which row gives a suitable starting material and reagent that can be used to prepare butanenitrile?

Nitrogen compounds

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

Chemical bonding

The infrared spectrum shown here was obtained from compound J. Which of the following statements about J is correct?

Chemical bonding

A portion of a polymer chain is shown. Which monomer is correct?

Chemical bonding

When answering this question, take into account structural isomerism and stereoisomerism. How many isomers are non-cyclic with the molecular formula $\text{C}_5\text{H}_{10}$?

Hydrocarbons

Compound Y is heated with an excess of dry HBr. What is the main product formed in the reaction?

Halogen compounds

Which reaction would form propanoic acid as one of the products?

Carboxylic acids and derivatives

Compound X is exposed to an excess of lithium aluminium hydride, and the reaction is permitted to proceed to completion. What is the structure of the organic product?

Carboxylic acids and derivatives

When $\text{CH}_3\text{CH}=\text{CHCH}_2\text{OH}$ is heated under reflux with $\text{K}_2\text{Cr}_2\text{O}_7/\text{H}^+$, what skeletal formula is formed for the compound produced?

Hydroxy compounds

In which molecule are there no bond angles of $90^\circ$ or $180^\circ$?

Chemical bonding

The diagram illustrates the structure of compound Q. Two of the rings, X and Y, each contain a $\text{C}=\text{C}$ bond. Which row is the correct one?

Chemical bonding

Carbon and nitrogen lie next to each other in the Periodic Table. Which properties do they both share?

The Periodic Table: chemical periodicity

Which properties are increased by the strong hydrogen bonding present in liquid water?

States of matter

A reaction involving carbon and oxygen is given. $\text{C(s)} + \frac{1}{2}\text{O}_2\text{(g)} \rightarrow \text{CO(g)}$ Which description correctly identifies the standard enthalpy change for this reaction?

Chemical energetics

Zinc reacts with hydrochloric acid. $\text{2HCl (aq)} + \text{Zn (s)} \rightarrow \text{ZnCl}_2 \text{ (aq)} + \text{H}_2 \text{ (g)}$ Which change would make this reaction faster but leave the Boltzmann distribution of molecular energies unchanged?

Reaction kinetics

The element astatine, At, lies beneath iodine in Group 17 of the Periodic Table. Which of the following statements about At are likely to be true?

Group 17

Which of the statements are correct?

Atoms, molecules and stoichiometry

Ethanal and hydrogen cyanide react with each other. Cyanide ions take part in the reaction mechanism. Which statements about this mechanism are correct?

Reaction kinetics

Which compounds give a yellow precipitate when tested with alkaline aqueous iodine?

Carbonyl compounds

Which statements are true for tetrafluoromethane?

Chemical bonding

Use the information below to answer this question. $\text{NaHCO}_3(s) + \text{HCl}(aq) \rightarrow \text{NaCl}(aq) + \text{H}_2\text{O}(l) + \text{CO}_2(g)$, $\Delta H = -38.97\ \text{kJ mol}^{-1}$ $\text{Na}_2\text{CO}_3(s) + 2\text{HCl}(aq) \rightarrow 2\text{NaCl}(aq) + \text{H}_2\text{O}(l) + \text{CO}_2(g)$, $\Delta H = -96.59\ \text{kJ mol}^{-1}$ When heated, sodium hydrogencarbonate breaks down as follows. $2\text{NaHCO}_3(s) \rightarrow \text{Na}_2\text{CO}_3(s) + \text{H}_2\text{O}(l) + \text{CO}_2(g)$ Determine the enthalpy change for this decomposition?

Chemical energetics

Which of the following statements comparing ethene and ethane are correct?

Chemical bonding

For the redox equation below, in what way do the oxidation states of vanadium and sulfur alter? $\text{VO}_2^+ + \text{SO}_2 \rightarrow \text{V}^{3+} + \text{SO}_4^{2-}$

Electrochemistry

The reaction equation for silver chloride with aqueous ammonia is given below. $\text{AgCl}(s) + 2\text{NH}_3(aq) \rightleftharpoons [\text{Ag(NH}_3)_2]^+(aq) + \text{Cl}^-(aq)$ State the units of $K_c$ for this reaction.

Equilibria

Sodium azide, $\text{NaN}_3$, breaks down as shown. $2\text{NaN}_3 \rightarrow 2\text{Na} + 3\text{N}_2$ What volume of nitrogen, measured at room temperature and pressure, is formed when $150\ \text{g}$ of sodium azide decomposes?

Atoms, molecules and stoichiometry

Research chemists have prepared a stable ion $\text{N}_5^+$. Which structure is most likely to represent the electron arrangement of this ion?

Chemical bonding

A sealed container contains $1.8\ \text{g}$ of water. When it is heated to $227^\circ\text{C}$, the water changes into steam at a pressure of $200\ \text{kPa}$. What is the container’s approximate volume?

States of matter

When Group 2 metals react with water, they produce alkaline solutions.

Group 2

The Group 17 elements chlorine, bromine and iodine are non-metals, and their physical and chemical properties follow clear trends.

Group 17

Glycerol, $\text{CH}_2(\text{OH})\text{CH(OH)}\text{CH}_2\text{OH}$, is used extensively in food manufacture and in pharmaceuticals. A sequence of reactions beginning with glycerol is shown.

Organic synthesis

Iron is a transition element in the fourth period. It forms compounds that contain the ions $\text{Fe}^{2+}$ and $\text{Fe}^{3+}$.

Chemistry of transition elements

State and explain the pattern in the thermal stability of the Group 2 carbonates down the group.

Group 2

Gold is a metal with very low reactivity, so it is oxidised only in particular conditions. The standard electrode potential, $E^\circ$, for $\text{Au}^{3+}(aq)/\text{Au}(s)$ is $+1.50\,\text{V}$.

Electrochemistry

Compound F has been discovered in small amounts in certain cereals and dried fruits.

Organic synthesis

Gallic acid, $\text{C}_7\text{H}_6\text{O}_5$, is an aromatic compound found in nature. Its structure is displayed.

Equilibria

Valinol may be made by the reactions shown below, with valine serving as the starting material in reaction 1.

Nitrogen compounds