O Level Chemistry 5070 Paper 11, Oct/Nov 2025

The pressure of a sample of air is reduced and its temperature remains constant. Which row describes the changes in the volume of the air and the distance between the particles in the air?

Which substance would diffuse most quickly? A carbon dioxide at $0{}^{\circ }\mathrm{C}$ B carbon dioxide at $25{}^{\circ }\mathrm{C}$ C neon at $0{}^{\circ }\mathrm{C}$ D neon at $25{}^{\circ }\mathrm{C}$

The main component of mineral X is calcium carbonate, ${\mathrm{C}\mathrm{a}\mathrm{C}\mathrm{O}}_3$. X also contains tiny grains of silicon(IV) oxide, ${\mathrm{S}\mathrm{i}\mathrm{O}}_2$. There are no other substances in X. Which row shows two correct statements about X?

The structure of hydroxylamine, ${\mathrm{N}\mathrm{H}}_2\mathrm{O}\mathrm{H}$, is shown. Which row about hydroxylamine is correct?

Metals lose electrons when they combine with a non-metal to form an ionic compound. Calcium combines with hydrogen to form the ionic compound calcium hydride, ${\mathrm{C}\mathrm{a}\mathrm{H}}_2$. How many electrons are there in the outer shell of each of the two hydride ions in ${\mathrm{C}\mathrm{a}\mathrm{H}}_2$? A 0 B 1 C 2 D 4

What is a property of diamond? A It can be used as a lubricant. B It has a melting point below $200{}^{\circ }\mathrm{C}$. C It has good electrical conductivity. D It is extremely hard.

Which statement about the bonding in copper is correct? A Copper atoms are attracted to a 'sea' of delocalised electrons. B Copper atoms are attracted to a shared pair of electrons. C Copper ions are attracted to a 'sea' of delocalised electrons. D Copper ions are attracted to a shared pair of electrons.

Aluminium ions, ${\mathrm{A}\mathrm{l}}^{3+}$, react with sulfate ions, ${\mathrm{S}\mathrm{O}}_4^{2-}$, to form aluminium sulfate. Which row shows the correct empirical formula and ionic formula of aluminium sulfate?

Which statement is correct? A The concentration of a solution is expressed in ${\mathrm{d}\mathrm{m}}^3\mathrm{/}\mathrm{m}\mathrm{o}\mathrm{l}$. B The empirical formula of a compound always gives the actual numbers of each type of atom in one molecule. C The molecular formula of a compound always contains more atoms than the empirical formula. D The relative atomic mass of an element is $\frac{\text{the average mass of one atom of the element}}{\frac{1}{12}\text{ the mass of one atom of carbon-12}}$.

How many atoms are there in $27.0\mathrm{g}$ of water, ${\mathrm{H}}_2\mathrm{O}$? A $9.030\times {10}^{23}$ B $1.806\times {10}^{24}$ C $2.709\times {10}^{24}$ D $3.612\times {10}^{24}$

A mixture of sodium hydrogencarbonate and sodium chloride is heated. The equation for the reaction that takes place when sodium hydrogencarbonate is heated is shown. $$2{\mathrm{N}\mathrm{a}\mathrm{H}\mathrm{C}\mathrm{O}}_3(\mathrm{s})\to {\mathrm{N}\mathrm{a}}_2{\mathrm{C}\mathrm{O}}_3(\mathrm{s})+{\mathrm{C}\mathrm{O}}_2(\mathrm{g})+{\mathrm{H}}_2\mathrm{O}(\mathrm{g})$$ Sodium chloride is unchanged on heating. When $6.0\mathrm{g}$ of the mixture is heated, the loss in mass is $1.5\mathrm{g}$. What is the percentage by mass of sodium hydrogencarbonate in the mixture? [relative molecular mass, $M_r$: ${\mathrm{N}\mathrm{a}\mathrm{H}\mathrm{C}\mathrm{O}}_3$, 84; ${\mathrm{N}\mathrm{a}}_2{\mathrm{C}\mathrm{O}}_3$, 106; ${\mathrm{C}\mathrm{O}}_2$, 44; ${\mathrm{H}}_2\mathrm{O}$, 18] A 34% B 48% C 68% D 95%

Electrolysis is used to plate a metal statue with silver. The statue is an electrode in a suitable electrolyte. Which row is correct?

Which row is correct?

Some bond energy data are given in the table.

Hydrazine, ${\mathrm{N}}_2{\mathrm{H}}_4$, reacts with oxygen, as shown. A value for the enthalpy change, $\mathrm{\Delta }H$, of this reaction is calculated by selecting and using data from the table. What is the value of $\mathrm{\Delta }H$? A $-728\mathrm{k}\mathrm{J}\mathrm{/}\mathrm{m}\mathrm{o}\mathrm{l}$ B $-568\mathrm{k}\mathrm{J}\mathrm{/}\mathrm{m}\mathrm{o}\mathrm{l}$ C $-34\mathrm{k}\mathrm{J}\mathrm{/}\mathrm{m}\mathrm{o}\mathrm{l}$ D $+352\mathrm{k}\mathrm{J}\mathrm{/}\mathrm{m}\mathrm{o}\mathrm{l}$

The rate of reaction between calcium carbonate and dilute hydrochloric acid is measured in three separate experiments. In experiment 1, the calcium carbonate is powdered, and an excess of hydrochloric acid is used. In experiment 2, the calcium carbonate is in lumps, and an excess of hydrochloric acid is used. In experiment 3, the calcium carbonate is in lumps, less hydrochloric acid is used, and the calcium carbonate is in excess. The results of these experiments are shown. Which statement is correct? A Experiment 1 is shown by curve X. B Experiment 1 is shown by curve Y. C Experiment 2 is shown by curve Y. D Experiment 3 is shown by curve Z.

The equation shows the reversible reaction between nitrogen and hydrogen to form ammonia. $${\mathrm{N}}_2+3{\mathrm{H}}_2\rightleftharpoons 2{\mathrm{N}\mathrm{H}}_3$$ The forward reaction is exothermic. Which statement is correct when the temperature is increased? A The activation energy increases. B The equilibrium shifts to form more ammonia. C The rate of the forward reaction decreases. D The rate at which ammonia decomposes increases.

Which statement is correct? A Ethanoic acid is a weak acid because when it is added to excess alkali not all of the ethanoic acid reacts. B Ethanoic acid is a weaker acid than sulfuric acid because a smaller proportion of its molecules dissociate in aqueous solution. C Hydrochloric acid is a stronger acid than ethanoic acid because hydrochloric acid always has a higher pH than ethanoic acid. D Sulfuric acid is a strong acid because it produces two hydrogen ions for every molecule that dissociates.

Some properties of a solid oxide are listed. ● It reacts with dilute sulfuric acid giving a salt and water. ● It is insoluble in water. ● It reacts with aqueous sodium hydroxide. Which oxide is being described? A aluminium oxide B magnesium oxide C phosphorus(V) oxide D sodium oxide

Two compounds are dissolved separately in water. When the two solutions are mixed, there is no observable change. What are the two compounds? A sodium chloride and barium nitrate B sodium chloride and lead nitrate C sodium sulfate and barium chloride D sodium sulfate and lead chloride

Part of the Periodic Table is shown. W, X, Y and Z are not the correct symbols of the elements. Which statement is correct? A The compound formed between X and W has covalent bonds. B W and Y are both gases at r.t.p. that contain covalent bonds. C X and Y react together more vigorously than Z and Y at r.t.p. D X and Z both have two outer-shell electrons.

The Group I metals lithium, sodium and potassium show trends in their melting points and in their reactions with water. Which statement is correct going down the group from lithium to potassium? A Their melting points decrease and their reaction with water becomes less vigorous. B Their melting points decrease and their reaction with water becomes more vigorous. C Their melting points increase and their reaction with water becomes less vigorous. D Their melting points increase and their reaction with water becomes more vigorous.

Chlorine gas is bubbled into separate samples of aqueous potassium iodide and aqueous potassium bromide. In which solutions is there a colour change?

Which statement about the elements in Group VIII of the Periodic Table is correct? A Going down the group, the number of electrons in the atom increases by eight for each noble gas. B Going down the group, the number of electrons in the outer shell increases by eight for each noble gas. C The number of electrons in the outer shell is the same for each noble gas. D The outer shell of each noble gas is fully occupied by electrons.

Which statement is correct? A Aluminium is used in food containers because of its resistance to corrosion. B Aluminium is used in the manufacture of aircraft because of its low ductility. C Copper is used in electrical wiring because of its high density. D Copper is used in the manufacture of overhead electrical cables because it forms an unreactive oxide layer.

Which elements are the major constituents of brass? A Br and As B Cu and Sn C Cu and Zn D Sn and Zn

The diagrams show two methods in which metal X is used to prevent the rusting of iron. A student suggests that metal X must be less reactive than iron and must have a lower proton number than iron. Which suggestions are correct?

Aluminium is extracted from molten aluminium oxide by electrolysis. Which material is used for the electrodes in the industrial extraction? A aluminium B carbon C cryolite D platinum

Which substance is used to remove odours in the treatment of the domestic water supply? A carbon B chlorine C fluorine D silver

Carbon dioxide, methane and oxygen are gases involved in the carbon cycle. Which of these gases cause global warming? A carbon dioxide only B carbon dioxide and methane C carbon dioxide and oxygen D methane only

How many structural isomers are there with the molecular formula ${\mathrm{C}}_4{\mathrm{H}}_9\mathrm{C}\mathrm{l}$? A 2 B 3 C 4 D 5

P is a branched hydrocarbon with the ratio of carbon atoms to hydrogen atoms being $1:2$. P has a relative molecular mass of 56. What is the identity of P?

Which row gives the correct names of the two compounds?

Which equation represents the reaction of ethane with chlorine in the presence of ultraviolet light? A ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_3+{\mathrm{C}\mathrm{l}}_2\to {\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_3\mathrm{C}\mathrm{l}+\mathrm{C}\mathrm{l}$ B ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_3+{\mathrm{C}\mathrm{l}}_2\to {\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2\mathrm{C}\mathrm{l}+\mathrm{H}\mathrm{C}\mathrm{l}$ C ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_3+{\mathrm{C}\mathrm{l}}_2\to {\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{l}\mathrm{C}\mathrm{H}}_2\mathrm{C}\mathrm{l}+{\mathrm{H}}_2$ D ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_3+{\mathrm{C}\mathrm{l}}_2\to {\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2+2\mathrm{H}\mathrm{C}\mathrm{l}$

Which compound reacts with hydrogen in an addition reaction? A ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}\mathrm{C}\mathrm{H}\mathrm{C}\mathrm{H}}_3$ B ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_3$ C ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}$ D ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2\mathrm{O}\mathrm{H}$

Which statement about carboxylic acids is correct? A They are prepared by the oxidation of alkanes. B They decolourise bromine water. C They react with alcohols to form esters. D They react with carbonates to form a salt, hydrogen and water.

The structures of X and Y are shown. What is the structure of the polymer formed when X and Y react together?

Which diagram shows a measuring cylinder?

A chromatogram of mixture X and pure substances P, Q, R and S is shown. Which statement is correct? A R is completely insoluble in the solvent used. B The $R_f$ value of Q is greater than the $R_f$ value of S. C X is a mixture of Q, R and S. D The paper is placed in the solvent with the solvent above the baseline.

Sulfur dioxide is a gas that is prepared by heating sodium sulfite with hydrochloric acid. It is an acidic gas. Sulfur dioxide is more dense than air. Which set of apparatus is suitable for preparing and collecting a dry sample of sulfur dioxide?

A colourless solution of compound W is tested separately with a few drops of aqueous sodium hydroxide and a few drops of aqueous ammonia. No precipitate is observed in either of the tests. What is the cation in W? A ${\mathrm{A}\mathrm{l}}^{3+}$ B ${\mathrm{C}\mathrm{a}}^{2+}$ C ${\mathrm{C}\mathrm{u}}^{2+}$ D ${\mathrm{N}\mathrm{H}}_4^{+}$