May/June 2023

For a change of state occurring at constant temperature and pressure: • energy is given out as stronger attractive forces develop between the particles • the mean separation between the particles alters only a little. Which change of state is being described?

Solids, liquids and gases

Which substance has a mass equal to that of one mole of water?

The mole and the Avogadro constant

A concentrated aqueous solution of sodium chloride is electrolysed with inert electrodes. Which row shows the changes in this electrolysis and the reason for them?

Electrolysis

Which statements concerning the energy changes in a chemical reaction are correct?

Exothermic and endothermic reactions

Two gases undergo reaction in a sealed vessel. Which change in conditions would make the reaction rate higher?

Rate of reaction

Catalysts alter the rate of chemical reactions. Which statements correctly describe what happens when a catalyst is added to a reaction?

Rate of reaction

The reaction equation for the Contact process is given below. $2\text{SO}_2(g) + \text{O}_2(g) \rightleftharpoons 2\text{SO}_3(g) \qquad \Delta H = -197\,\text{kJ mol}^{-1}$ The reaction is carried out at $450^\circ\text{C}$, $2$ atmospheres pressure and in the presence of a catalyst. What happens if the temperature is lowered to $250^\circ\text{C}$ and the catalyst is taken away?

Reversible reactions and equilibrium

Universal indicator is made up of several dyes. The reversible reaction for one dye, $\text{IndOH}$, is shown. $\text{IndOH}(aq) + \text{H}^+(aq) \rightleftharpoons \text{Ind}^+(aq) + \text{H}_2\text{O}(l)$ A few drops of universal indicator solution are placed into $50\,\text{cm}^3$ of water. Then a few drops of dilute hydrochloric acid are added to this mixture. Which row shows what occurs when the acid is added?

The characteristic properties of acids and bases

Methane combustion is a redox reaction. $\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O}$ Which of the following statements about this reaction is correct?

Redox

Which preparation method for magnesium sulfate is an example of a redox reaction?

Redox

Samples of $\text{HCl}(aq)$ and $\text{HNO}_3(aq)$ are examined with universal indicator paper. The $\text{HCl}(aq)$ sample shows a pH of $4$, while the $\text{HNO}_3(aq)$ sample shows a pH of $2$. Which statement is correct?

The characteristic properties of acids and bases

X, Y and Z are chemical elements. X and Y are located in the same period of the Periodic Table. Y and Z are located in the same group of the Periodic Table. What could be the electronic configurations of X, Y and Z?

Atomic structure and the Periodic Table

Which two substances combine to produce only a salt and water?

The characteristic properties of acids and bases

In the Periodic Table, the elements are organised into groups and periods. Which row is correct?

Atomic structure and the Periodic Table

Sodium, potassium and rubidium belong to Group I of the Periodic Table. Chlorine, bromine and iodine belong to Group VII. Which statement is correct?

Arrangement of elements

Which statement concerning transition elements and their compounds is true?

Transition elements

Three statements concerning the properties of metals are shown. 1 All metals conduct electricity. 2 All metals have two electrons in their innermost shell. 3 All metals have high melting points. Which statements are correct?

Properties of metals

Which of the following statements about metals and their uses are correct? 1 Aluminium is used to produce overhead electrical cables because of its low density. 2 Aluminium is used to produce food containers because it resists corrosion. 3 Copper is used for electrical wiring because it is ductile.

Uses of metals

Stainless steel is an alloy. It is made from iron plus more than one additional element. Which elements, apart from iron, are commonly present in stainless steel?

Alloys and their properties

The equations for several reactions involving metals Q, R and T are shown below. $\text{2QNO}_3(aq) + \text{Cu}(s) \rightarrow \text{2Q}(s) + \text{Cu(NO}_3)_2(aq)$ $\text{R}(s) + \text{TSO}_4(aq) \rightarrow \text{T}(s) + \text{RSO}_4(aq)$ $\text{T}(s) + \text{H}_2\text{SO}_4(aq) \rightarrow \text{TSO}_4(aq) + \text{H}_2(g)$ From these equations, what is the reactivity order of Q, R and T?

Reactivity series

Zinc is used to galvanise iron, which stops the iron from rusting. Which of these statements are correct? 1 The zinc layer acts as a barrier separating the iron from oxygen and water in the air. 2 Zinc oxidises before the iron does, even if the zinc layer is scratched. 3 When iron rusts, iron atoms gain electrons and form ions.

Corrosion of metals

Three statements about aluminium extraction are listed below. 1 The electrolyte consists of aluminium oxide dissolved in molten cryolite. 2 Carbon is used for both the cathode and the anode. 3 Carbon dioxide is released at the cathode. Which of these statements are correct?

Extraction of metals

The electron, proton and neutron counts for four different particles are shown. Which of the particles are isotopes of the same element?

Isotopes

What is one cause of deoxygenation of lake water?

Water

Dissolved substances may lead to eutrophication and deoxygenation of water. How many of the ions shown here cause this effect? $\text{Cl}^-$, $\text{CO}_3^{2-}$, $\text{Na}^+$, $\text{NO}_3^-$, $\text{PO}_4^{3-}$

Water

Which of the following statements about global warming is correct?

Air quality and climate

The displayed diagrams show the structures of three compounds, W, X and Y. Which of the following statements about these three compounds are correct? 1 W and Y are both alcohols, while X is a carboxylic acid. 2 W, X and Y all have the same molecular formula. 3 W and Y are structural isomers of each other.

Formulae, functional groups and terminology

What is the displayed formula for propyl methanoate?

Naming organic compounds

The table lists some fractions produced by the fractional distillation of petroleum together with their uses. Which rows are correct?

Fuels

Which equation represents the reaction between ethane and chlorine when ultraviolet light is present?

Alkanes

Hexan-3-ol belongs to the alcohols. How many molecules of oxygen are required for the complete combustion of one molecule of hexan-3-ol?

Alcohols

An organic compound, $P$, is in aqueous solution. The solution has a concentration of $0.1\,\text{mol dm}^{-3}$ and a pH of $3$. A solid is then added to the solution and fizzing is observed. Which equation could represent this reaction?

The characteristic properties of acids and bases

A paper chromatography investigation is carried out to determine an $R_f$ value for $\text{Fe}^{3+}(aq)$. The chromatogram is shown. To make the spot that contains $\text{Fe}^{3+}(aq)$ easier to see, the paper is sprayed with aqueous sodium hydroxide so that iron(III) hydroxide precipitate is produced. In the chromatogram, the $R_f$ of $\text{Fe}^{3+}(aq)$ is shown by ......1...... and the colour of the precipitate is ......2...... . Which row gives the correct answers for gaps 1 and 2?

Chromatography

Several statements concerning the bonding in magnesium chloride are given below. Which statements are correct?

Ion and ionic bonds

A laboratory contains a powdered blend of solid iodine and solid carbon. Iodine is very soluble in hexane and only slightly soluble in water. Carbon is insoluble in both solvents. One portion of the mixture is shaken with hexane. This is $X$. A different portion of the mixture is shaken with water. This is $Y$. Which procedure is used to obtain a pure sample of iodine?

Separation and purification

Ethane, $\text{C}_2\text{H}_6$, and ammonia, $\text{NH}_3$, are covalent compounds. The dot-and-cross diagrams for these compounds are displayed. Which statements are true?

Simple molecules and covalent bonds

If a piece of copper is added to aqueous silver nitrate, a displacement reaction occurs. What is the ionic equation for the reaction that occurs?

Redox

The following three compounds are given: • calcium carbonate • potassium sulfate • zinc nitrate In which row is the element that makes up the largest percentage by mass in each compound shown? [$A_r$: Ca, $40$; C, $12$; O, $16$; K, $39$; S, $32$; Zn, $65$; N, $14$]

Relative masses of atoms and molecules

The two aqueous solutions, Q and R, match in concentration when this is expressed in $\text{mol dm}^{-3}$. Solution Q includes $4.0\,\text{g}$ of NaOH in $500\,\text{cm}^3$ of solution. Which one could be solution R? [$A_r$: Na, $23$; O, $16$; H, $1$]

The mole and the Avogadro constant

Two hydrated compounds are first weighed, then heated so that water of crystallisation is removed. The resulting anhydrous compounds are weighed, and the measurements are listed below. $3.97\,\text{g FeSO}_4\cdot x\text{H}_2\text{O}$ produces $2.17\,\text{g}$ of anhydrous $\text{FeSO}_4$. $2.88\,\text{g CaSO}_4\cdot y\text{H}_2\text{O}$ produces $2.27\,\text{g}$ of anhydrous $\text{CaSO}_4$. What are the values of $x$ and $y$? $[M_r: \text{FeSO}_4, 152; \text{CaSO}_4, 136; \text{H}_2\text{O}, 18]$

The mole and the Avogadro constant

Iodine is present in a sample at room temperature and pressure. Which statement about the particles in this sample is correct?

Solids, liquids and gases

The diagram illustrates the structures of the atoms of two elements, X and Z. X and Z are not the atomic symbols used for these elements. The elements combine to make a compound. What is the mass of 1 mole of this compound?

Relative masses of atoms and molecules

Which compound has a nitrogen mass percentage of $45.2\%$? $[A_r: \text{C}, 12; \text{H}, 1; \text{N}, 14]$

Relative masses of atoms and molecules

Aqueous copper(II) sulfate is electrolysed with copper electrodes. The current remains constant, and the anode is measured at regular intervals of time. Which graph is produced when the mass of the anode is plotted against time?

Electrolysis

In a hydrogen-oxygen fuel cell, what chemical product is formed?

Hydrogen–oxygen fuel cells

Hydrogen may be obtained by reacting methane with steam. $\text{CH}_4 + 2\text{H}_2\text{O} \rightarrow \text{CO}_2 + 4\text{H}_2$ With the bond energies shown in the table, what is the enthalpy change of reaction, $\Delta H$?

Exothermic and endothermic reactions

Which method would be most effective for reducing the rate of the reaction between magnesium and sulfuric acid?

Rate of reaction

The gas volume formed when $100\,\text{cm}^3$ of hydrochloric acid reacts with excess calcium carbonate is recorded in two experiments. The gas volumes are taken at r.t.p., and the findings are displayed. Which single change in the conditions for experiment 1 would produce the results shown for experiment 2? Assume that every other condition stays the same.

The mole and the Avogadro constant

Hydrogen is produced on an industrial scale by the reaction below. $\text{CO}(g) + \text{H}_2\text{O}(g) \rightleftharpoons \text{CO}_2(g) + \text{H}_2(g) \qquad \Delta H = -41\,\text{kJ mol}^{-1}$ Several statements about this industrial process are listed. Which of them are correct?

Reversible reactions and equilibrium

The table shows two important industrial reactions involving gases. Which catalysts are stated correctly?

Rate of reaction

Iron(II) ions undergo reaction with chlorine. $2\text{Fe}^{2+}(aq) + \text{Cl}_2(g) \rightarrow 2\text{Fe}^{3+}(aq) + 2\text{Cl}^-(aq)$ Which statement is correct for this reaction?

Redox

Element Z, nucleon number $31$, forms the ion $Z^{3-}$. In which part of the Periodic Table is Z located?

Atomic structure and the Periodic Table

Which reagent and which observation are used for the test for a reducing agent?

Redox

At room temperature, compound X is a gas. When X dissolves in water, the resulting solution has a pH of 4. Which statement about compound X is correct?

The characteristic properties of acids and bases

Which of the following statements about hydrochloric acid is correct?

The characteristic properties of acids and bases

Which two equations account for the fact that adding calcium hydroxide to soil lowers its acidity but also lowers fertiliser efficiency?

The characteristic properties of acids and bases

Which anions are present in salts that are always soluble in water?

Ion and ionic bonds

The element phosphorus, $P$, lies directly beneath nitrogen in the Periodic Table. It forms an oxide with the empirical formula $P_2O_5$. Using phosphorus’s position in the Periodic Table, the element would be expected to be .....1..... and the bonds in its oxide to be .....2...... Which words correctly fill gaps 1 and 2?

Arrangement of elements

Which one of the statements is correct?

Elements, compounds and mixtures

The table gives some properties of transition elements and explains why they have them. Which row shows a correct property and the reason transition elements display this property?

Transition elements

Which equation is the correct one?

Formulae

Metal X reacts with cold water and gives off a gas. Zinc can displace metal Y from a solution of its salts. The carbonate of metal Z does not dissolve. Which metals could X, Y and Z be?

Reactivity series

Naturally occurring bromine has a relative atomic mass of $80$ and is made up entirely of two isotopes with relative atomic masses $79$ and $81$. What conclusion can be drawn about naturally occurring bromine from this information alone?

Isotopes

Which one of the statements about alloys is correct?

Alloys and their properties

Small pieces of magnesium may be fixed onto the steel hull of a ship in order to stop rust from forming. This is known as sacrificial protection. Which of the following statements about sacrificial protection are correct?

Corrosion of metals

What makes carbon suitable for water purification?

Water

Which statement regarding air pollutants is correct?

Air quality and climate

What structural formula represents propyl methanoate?

Naming organic compounds

Which statement about ethane is true?

Alkanes

Isoprene is an alkene that occurs commonly in plants. Which properties are shown by isoprene?

Alkenes

An ester structure is illustrated. Which two compounds react together to make this ester?

Carboxylic acids

A sample of $25.0\,\text{cm}^3$ of $1.0\,\text{mol dm}^{-3}$ sodium hydroxide is titrated using dilute sulfuric acid and a suitable indicator. Reaching the end-point needs $25.0\,\text{cm}^3$ of the acid. What is the concentration of the sulfuric acid and which indicator is used?

Acid–base titrations

The outcomes from a paper chromatography experiment are displayed. X is an aqueous solution containing a salt of a Group I element. Y is an aqueous solution containing a salt of a transition element. Which row is correct?

Chromatography

Element X and element Y combine to make a compound. The electronic configurations for X and Y are X = $2,8,3$ and Y = $2,6$. Which row indicates the electron transfer that occurs and the kind of compound produced?

Ion and ionic bonds

Aqueous sodium hydroxide is used to identify the ions present in the aqueous solutions of compounds Q and R. The outcomes are displayed. Which row is correct?

Identification of ions and gases

Which molecule contains the greatest number of electrons participating in covalent bonds?

Simple molecules and covalent bonds

X is the bond pattern surrounding a carbon atom in graphite. Y is the bond pattern surrounding a carbon atom in diamond. Z is the bond pattern surrounding a silicon atom in silicon(IV) oxide, $\text{SiO}_2$. Which of these arrangements of bonds are identical?

Giant covalent structures

What chemical equation represents the reaction of sodium carbonate with dilute nitric acid?

The characteristic properties of acids and bases

Which statements concerning relative atomic mass and relative molecular mass are correct?

Relative masses of atoms and molecules

Aqueous hydrogen peroxide, $\text{H}_2\text{O}_2$, breaks down slowly at $25^\circ\text{C}$. $2\text{H}_2\text{O}_2(aq) \rightarrow 2\text{H}_2\text{O}(l) + \text{O}_2(g)$ When a catalyst is introduced, this decomposition occurs more quickly. A student adds a small quantity of catalyst to $10\,\text{cm}^3$ of $1.0\,\text{mol dm}^{-3}$ $\text{H}_2\text{O}_2(aq)$ and then collects the gas produced. The collected gas has a volume of $90\,\text{cm}^3$. All measurements are taken at room temperature and pressure. What is the percentage yield of $\text{O}_2(g)$?

The mole and the Avogadro constant

Select the answers from the oxides listed below. Al$_2$O$_3$ Co CO$_2$ CaO Fe$_2$O$_3$ H$_2$O Na$_2$O SO$_2$ SiO$_2$ Each oxide may be used once, more than once or not at all. State which oxide:

Oxides

PVC and poly(propene) are polymers formed by a reaction known as addition polymerisation.

Polymers

Group I is made up of the elements lithium, sodium and potassium.

Group I properties

This question concerns how salts are made.

Preparation of salts

This question focuses on compounds that include phosphorus.

Ion and ionic bonds

When heated, ammonium chloride breaks down to form hydrogen chloride and ammonia. The reaction can proceed in both directions, and the forward change takes in thermal energy. $\text{NH}_4\text{Cl}(s) \rightleftharpoons \text{HCl}(g) + \text{NH}_3(g)$

Reversible reactions and equilibrium

This question concerns the energy changes that occur during chemical reactions.

Exothermic and endothermic reactions

Methanol, propan-1-ol and propan-2-ol belong to the alcohol family. Fig. 7.1 shows the displayed formulae for methanol and propan-1-ol.

Alcohols

This question concerns electrolysis.

Electrolysis

Nitrogen oxides, for instance nitrogen monoxide, NO, are pollutants in the atmosphere. In the exhaust from a car engine, nitrogen monoxide accounts for 0.00200% by volume.

Air quality and climate

Select one oxide from the list below to answer the questions. CO CO$_2$ CaO CuO Fe$_2$O$_3$ H$_2$O SO$_2$ SiO$_2$ ZnO Use each oxide no more than once, more than once, or not at all. State which oxide:

Oxides

Proteins and PET are polymers formed by a reaction known as condensation polymerisation.

Polymers

The elements in Group VII are fluorine, chlorine, bromine and iodine.

Group VII properties

This question concerns how salts are prepared.

Preparation of salts

This question focuses on compounds made from magnesium and nitrogen.

Ion and ionic bonds

Carbon reacts with steam to form carbon monoxide and hydrogen. This reaction is reversible, and the forward reaction takes in thermal energy. $\text{C}(s) + \text{H}_2\text{O}(g) \rightleftharpoons \text{CO}(g) + \text{H}_2(g)$

Reversible reactions and equilibrium

This question concerns the energy transfers that occur in chemical reactions.

Exothermic and endothermic reactions

Ethene, but-1-ene and but-2-ene belong to the alkene family. Figure 7.1 shows the displayed formulae for ethene and but-1-ene.

Alkenes

This question concerns electrolysis.

Electrolysis

By volume, a sample of clean, dry air contains 0.0400% carbon dioxide.

The mole and the Avogadro constant

A student is using chromatography to separate the dyes in a food colouring. Fig. 1.1 shows the apparatus that the student uses.

Chromatography

White vinegar is a colourless solution of ethanoic acid. A student carries out titrations of $0.400\,\text{mol dm}^{-3}$ aqueous sodium hydroxide with two vinegar samples, A and B. Four titrations are done in total, two with A and two with B. The student: Step 1 uses a volumetric pipette to place $25.0\,\text{cm}^3$ of $0.400\,\text{mol dm}^{-3}$ sodium hydroxide into a conical flask. Step 2 adds five drops of an indicator to the conical flask. Step 3 runs A from a burette into the flask while swirling the contents, then adds it drop by drop close to the end-point until the solution just changes colour. Step 4 empties the conical flask and rinses it with distilled water. Step 5 repeats steps 1 to 4. Step 6 repeats steps 1 to 5 using B instead of A.

Acid–base titrations

A student carries out an investigation using solution W and copper(II) carbonate.

Identification of ions and gases

Baking powder helps cakes to expand. If water is mixed with baking powder, carbon dioxide gas is given off. The longer baking powder has been kept, the less carbon dioxide it gives off when water is added. Plan an investigation to determine which of two different samples of baking powder has been kept for a longer time. Your plan should include: • the apparatus needed • the method to use • the measurements to take • the variables to control • how to use the results to work out which sample has been kept for longer. You may draw a diagram to help answer the question.

Experimental design

A student is investigating rusting in iron. Fig. 1.1 displays the apparatus used by the student.

Corrosion of metals

A student carries out an investigation on solution W and solid X.

Identification of ions and gases

Baking soda helps bread rise. When baking soda is heated, it breaks down and carbon dioxide gas is given off. Baking soda also breaks down slowly while it is stored. The longer it is stored, the less carbon dioxide it gives off when heated. Plan an investigation to show which of two different samples of baking soda has been stored for longer. Your plan should include the use of common laboratory apparatus and the two samples of baking soda. No other chemicals are to be used. Your plan should include: - the apparatus needed - the method to use - the measurements to take - the variables to control - how to use the results to decide which sample has been stored for longer. You may draw a diagram to help you answer the question.

Experimental design