O Level Chemistry 5070/11, May/June 2025

5070/11 · May/June 2025

Four gases are listed. 1 $C H_{4}$ 2 $N H_{3}$ 3 $C O_{2}$ 4 $N_{2}$ What is the order of their rate of diffusion at room temperature and pressure? slowest $⟶$ fastest A 1 2 4 3 B 2 1 3 4 C 3 4 2 1 D 4 1 3 2

Sodium is added to water and a chemical reaction occurs. Hydrogen and aqueous sodium hydroxide are produced. Which row describes the reactants and products in this reaction?

	reactants and products that are elements	reactants and products that are compounds	reactants and products that are mixtures
A	hydrogen	water and sodium	aqueous sodium hydroxide
B	hydrogen and sodium	water	aqueous sodium hydroxide
C	aqueous sodium hydroxide	hydrogen and sodium	water
D	sodium and water	aqueous sodium hydroxide	hydrogen

An atom of element X is shown. Which element is X? A beryllium B boron C carbon D magnesium

Which definition of isotopes is correct? A atoms of different elements that have the same number of electrons B atoms of different elements that have the same number of neutrons C atoms of the same element that have different numbers of electrons D atoms of the same element that have different numbers of neutrons

A pure sample of element X has a relative atomic mass of 51.8. The sample consists of three isotopes. The table shows the relative masses and percentage abundances of two of the isotopes.

relative mass of isotope	percentage abundance of isotope
50	40
55	20

What is the relative mass of the third isotope? A 51 B 52 C 53 D 54

Magnesium reacts with oxygen to form magnesium oxide. $2 M g + O_{2} \to 2 M g O$ Which row is correct?

	structure of $M g$	structure of $O_{2}$	$M g^{2 +}$	$O^{2 -}$
A	giant lattice	simple molecules	anion	cation
B	simple molecules	giant lattice	anion	cation
C	giant lattice	simple molecules	cation	anion
D	simple molecules	giant lattice	cation	anion

Which statement about solid calcium chloride is correct? A It conducts electricity. B It has a low melting point. C It has an ionic lattice structure. D It is insoluble in water.

Which description of metallic bonding is correct? A the electrostatic attraction between negative ions in a lattice and a 'sea' of electrons B the electrostatic attraction between negative ions in a lattice and a 'sea' of protons C the electrostatic attraction between positive ions and negative ions in a lattice D the electrostatic attraction between positive ions in a lattice and a 'sea' of electrons

The ions $C a^{2 +}$ and $P O_{4}^{3 -}$ combine to form an ionic compound. What is the formula of the compound? A $C a_{2} P O_{4}$ B $C a (P O_{4})_{3}$ C $C a_{2} (P O_{4})_{3}$ D $C a_{3} (P O_{4})_{2}$

Magnesium reacts with aqueous copper(II) sulfate to form copper and aqueous magnesium sulfate. What is the correct equation for this reaction? A $M g + C u S O_{4} \to C u + M g S O_{4}$ B $M g + C u_{2} S O_{4} \to 2 C u + M g S O_{4}$ C $2 M g + C u S O_{4} \to C u + M g_{2} S O_{4}$ D $2 M g + C u_{2} S O_{4} \to 2 C u + M g_{2} S O_{4}$

An organic compound has an $M_{r}$ of 88. What is the molecular formula of this compound? A $C_{10} H_{20} O$ B $C_{5} H_{10} O$ C $C_{4} H_{8} O_{2}$ D $C_{2} H_{4} O$

$10 {cm}^{3}$ of hydrogen gas is mixed with $x {cm}^{3}$ of chlorine gas. The equation for the reaction that takes place is shown. $H_{2} (g) + C l_{2} (g) \to 2 H C l (g)$ All the hydrogen reacts. The total volume of gas at the end of the reaction is $40 {cm}^{3}$ . All measurements are at room temperature and pressure. What is the value of $x$ ? A $10 {cm}^{3}$ B $20 {cm}^{3}$ C $30 {cm}^{3}$ D $40 {cm}^{3}$

$100 {cm}^{3}$ of aqueous potassium hydroxide with a concentration of $1.00 mol / {dm}^{3}$ reacts with excess dilute sulfuric acid. $2 K O H (a q) + H_{2} S O_{4} (a q) \to K_{2} S O_{4} (a q) + 2 H_{2} O (l)$ $3.48 g$ of pure anhydrous potassium sulfate is produced. What is the percentage yield of potassium sulfate? A $5 %$ B $10 %$ C $20 %$ D $40 %$

Which statement about electrolysis is correct? A Negative anions move towards the positive cathode. B Negative cations move towards the positive cathode. C Positive anions move towards the negative cathode. D Positive cations move towards the negative cathode.

The diagram shows an electrolysis experiment using inert electrodes. Which row shows what happens to the concentration of the electrolyte in L and in M as the electrolysis proceeds?

	L	M
A	✗	✗
B	✗	✓
C	✓	✗
D	✓	✓

key ✓ = concentration stays constant ✗ = concentration does not stay constant

Which row is correct for a chemical reaction in which $Δ H$ is negative?

	bond energy change	type of reaction
A	energy of bonds broken greater than energy of bonds formed	endothermic
B	energy of bonds broken less than energy of bonds formed	exothermic
C	energy of bonds broken greater than energy of bonds formed	exothermic
D	energy of bonds broken less than energy of bonds formed	endothermic

The diagram shows apparatus used to investigate two different reactions that produce gases. The reactants for each experiment are mixed and the mass of flask plus contents for each experiment is recorded every 30 seconds. A graph of the mass against time is drawn. In experiment 1, solid X is calcium carbonate. In experiment 2, solid X is magnesium. Which graph is correct? A B C D

In a closed flask, gases Q and R reach a dynamic equilibrium. $Q (g) ⇌ 2 R (g) Δ H is positive$ Which change will move the equilibrium to the right? A adding a catalyst B decreasing the temperature C increasing the pressure D increasing the volume of the flask

Which row shows the typical conditions used for the conversion of sulfur dioxide to sulfur trioxide in the Contact process?

	catalyst	pressure / kPa
A	iron	20 000
B	iron	200
C	vanadium(V) oxide	20 000
D	vanadium(V) oxide	200

The pH of dilute ethanoic acid is measured. The equation for the partial dissociation of ethanoic acid is shown. $C H_{3} C O O H (a q) ⇌ C H_{3} C O O^{-} (a q) + H^{+} (a q)$ Aqueous sodium ethanoate, $C H_{3} C O O N a$ , is added to the dilute ethanoic acid and the pH is measured again. What is the initial pH of the dilute ethanoic acid and how does it change after the addition of the aqueous sodium ethanoate?

	initial pH	change in pH after adding aqueous sodium ethanoate
A	3–4	increases
B	3–4	decreases
C	8–9	increases
D	8–9	decreases

Which element reacts with oxygen to produce an amphoteric oxide? A carbon B copper C sulfur D zinc

Element X is in Period 2 of the Periodic Table. X reacts with magnesium to form an ionic compound with the formula $M g X_{2}$ . What is X? A chlorine B fluorine C oxygen D sulfur

Rubidium is an element in Group I of the Periodic Table. Which statement about rubidium is correct? A It has a higher melting point than potassium. B It reacts with water to produce an acidic solution. C It reacts with water to produce oxygen gas. D It is more reactive than potassium.

Which statement is correct? A Noble gases are unreactive because they all have eight electrons in their outer shells. B The Group VII element astatine, $A t_{2}$ , is expected to be a black solid at room temperature. C The reactivity of the elements in both Group I and Group VII increases down the group. D When aqueous chlorine is added to aqueous potassium bromide, there is no change in colour.

M is a metal that forms coloured compounds. M is extracted from its oxide either by heating with carbon or by electrolysis. M reacts with dilute hydrochloric acid. What is M? A copper or magnesium B copper only C iron or magnesium D iron only

Which statement about brass is correct? A It is a compound. B It is an alloy. C It is an isomer. D It is an isotope.

Iron is galvanised with zinc to prevent rusting. Which type of protection is provided by galvanising? A alloy formation B barrier and sacrificial C barrier only D sacrificial only

Iron is extracted from its ore hematite in a blast furnace. Which statement about this extraction process is correct? A Air is blown into the blast furnace to react with carbon. B At the bottom of the blast furnace, a layer of molten iron floats on top of a layer of molten slag. C Limestone is decomposed in the blast furnace to produce carbon monoxide. D Silicon dioxide, an impurity in the ore, is a basic oxide.

Chlorine and carbon are both used in the treatment of the domestic water supply. Which row describes one reason for the use of each substance?

	chlorine	carbon
A	causes the sedimentation of some solids	removes tastes from the water
B	causes the sedimentation of some solids	removes dissolved oxygen from the water
C	kills some microbes	removes tastes from the water
D	kills some microbes	removes dissolved oxygen from the water

Which row states an adverse effect for the named pollutant?

	air pollutant	adverse effect
A	carbon dioxide	increases plant growth
B	methane	causes cancer
C	oxides of nitrogen	photochemical smog
D	particulates	acid rain

Three statements about global warming and greenhouse gases are listed. 1 Global warming is occurring because more of the Earth's thermal energy is released to space. 2 Greenhouse gases both absorb and emit thermal energy. 3 Greenhouse gas levels in the atmosphere may be reduced by replacing fossil fuels with hydrogen. Which statements are correct? A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

Which compound is an alcohol? A B C D

An ester has the structural formula $C H_{3} C O O C H_{2} C H_{2} C H_{3}$ . What is the name of this ester? A ethyl propanoate B methyl propanoate C propyl ethanoate D propyl methanoate

Petroleum is separated into fractions in a fractionating column. Which property of the fractions increases from the bottom to the top of the column? A boiling point B chain length C viscosity D volatility

Three statements about alkanes are listed. 1 They contain carbon and hydrogen only. 2 They contain only single covalent bonds. 3 They are saturated hydrocarbons. Which statements are correct? A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 3 only

The flowchart shows some reactions of hydrocarbons. $saturated hydrocarbon with large molecules \overset{process 1}{\to} unsaturated hydrocarbons with small molecules \to_{+ H_{2}}^{condition 2} saturated hydrocarbons with small molecules$ Which row is correct?

	process 1	condition 2
A	cracking	heat with nickel catalyst
B	fractional distillation	heat with acid catalyst
C	cracking	heat with acid catalyst
D	fractional distillation	heat with nickel catalyst

The structure of a condensation polymer is shown. Which two monomers form this polymer? A $H_{2} N C H_{2} C H_{2} N H_{2}$ and $H O O C C H_{2} C O O H$ B $H_{2} N C H_{2} C H_{2} N H_{2}$ and $H O O C C H_{2} C H_{2} C O O H$ C $H_{2} N C H_{2} N H_{2}$ and $H O O C C H_{2} C H_{2} C O O H$ D $H_{2} N C H_{2} N H_{2}$ and $H O O C C H_{2} C O O H$

A titration is completed. $25.0 {cm}^{3}$ of aqueous sodium hydroxide is added to a conical flask. A few drops of methyl orange indicator are added. Dilute hydrochloric acid is added slowly to the mixture until the colour changes. Which row is correct?

	apparatus used to add alkali	apparatus used to add acid	colour change of indicator
A	volumetric pipette	burette	red to orange
B	measuring cylinder	burette	red to orange
C	volumetric pipette	burette	yellow to orange
D	volumetric pipette	measuring cylinder	yellow to orange

An impure sample of compound X has a melting point of $120^{\circ} C$ . X is purified and its melting point is measured again. Which row is correct?

	method of purifying X	melting point of pure X / $^{\circ} C$
A	crystallisation	125
B	crystallisation	115
C	distillation	125
D	distillation	115

Samples of two compounds, P and Q, are tested. The result of each test is shown.

test	P	Q
add dilute hydrochloric acid	gas given off that turns limewater milky	no observable change
acidify with dilute nitric acid then add aqueous barium nitrate	no precipitate forms	white precipitate
add aqueous sodium hydroxide	no observable change	green precipitate, soluble in excess
add aqueous ammonia	no observable change	green precipitate, insoluble in excess
flame test	lilac flame	not tested

Which row shows the identities of the ions present in P and Q?

	P	Q
A	$K^{+}$ and $S O_{4}^{2 -}$	$C r^{3 +}$ and $C O_{3}^{2 -}$
B	$K^{+}$ and $C O_{3}^{2 -}$	$F e^{2 +}$ and $S O_{4}^{2 -}$
C	$K^{+}$ and $C O_{3}^{2 -}$	$C r^{3 +}$ and $S O_{4}^{2 -}$
D	$L i^{+}$ and $C O_{3}^{2 -}$	$C r^{3 +}$ and $S O_{4}^{2 -}$

O Level Chemistry 5070 Paper 11, May/June 2025

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