Chemistry HL Paper 1A, November 2025, TZ1

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Zadanie 1

Which methods for separating the components of the given mixtures are correct? A. I and II only B. I and III only C. II and III only D. I, II and III

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Zadanie 2

Bromine is a diatomic element made up of two isotopes, $\ce{^{79}Br}$ and $\ce{^{81}Br}$, in an approximately 1 : 1 ratio. Which graph shows the full mass spectrum of bromine? A. Graph A B. Graph B C. Graph C D. Graph D

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Zadanie 3

The diagrams show the 3s and 3p sublevels of a sulfur atom; the inner sublevels are full. Which diagram represents the ground-state electron configuration, in agreement with the Pauli exclusion principle and Hund's rule? A. Diagram A B. Diagram B C. Diagram C…

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Zadanie 4

4.06 g of hydrated magnesium chloride, MgCl₂ ⋅ 6 H₂O (M_r = 203), is dissolved in water to make 0.250 dm³ of solution. What is the concentration of chloride ions, in mol dm⁻³, in this solution? A. 0.0400 B. 0.0800 C.…

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Zadanie 5

Under which conditions does the gas behave most like an ideal gas? A. Helium at 200 kPa and 300 K B. Helium at 20 kPa and 600 K C. Sulfur dioxide at 20 kPa and 600 K D. Sulfur dioxide at 200 kPa and 300 K

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Zadanie 6

Part of the lattice of potassium bromide, KBr, is shown in an expanded view. Which statement about the lattice of potassium bromide is correct? A. Each bromide ion is in contact with six potassium ions. B. Neighbouring ions are held together by shared pairs of…

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Zadanie 7

What are the electron domain geometry and the molecular geometry of the BrF₄⁻ ion? A. Electron domain geometry: tetrahedral; molecular geometry: tetrahedral B. Electron domain geometry: trigonal bipyramidal; molecular geometry: seesaw C. Electron domain…

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Zadanie 8

Which orbitals overlap to form the σ-bond and the two π-bonds between carbon and nitrogen in hydrogen cyanide, HCN? A. σ-bond: sp and sp³; π-bonds: p and p B. σ-bond: sp and sp; π-bonds: p and p C. σ-bond: sp…

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Zadanie 9

Which species contain a coordination bond? I. CO II. H₃O⁺ III. BF₃ A. I and II only B. I and III only C. II and III only D. I, II and III

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Zadanie 10

Which Lewis formula of the sulfate ion, SO₄²⁻, is preferred on the basis of formal charges? A. Formula A B. Formula B C. Formula C D. Formula D

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Zadanie 11

Which statement best explains why aluminium can be drawn into thin wires? A. The delocalized electrons carry charge through the metal. B. The layers of aluminium ions can slide over each other while the delocalized electrons keep the lattice bonded. C.…

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Zadanie 12

Which substance is a good conductor of electricity in the solid state? A. Graphene B. Diamond C. Silicon dioxide D. Silicon

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Zadanie 13

What is the IUPAC name of the compound shown? A. 3-methylhexan-4-one B. 4-methylhexan-3-one C. 4-ethylpentan-3-one D. 2-ethylpentan-3-one

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Zadanie 14

What are the oxidation states of the elements in K₂MnO₄? A. K: +1, Mn: +6, O: −2 B. K: +1, Mn: +7, O: −2 C. K: +2, Mn: +4, O: −2 D. K: +1, Mn: +6, O: −1

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Zadanie 15

Which statement is correct for the group 17 elements from chlorine to iodine? A. The first ionization energy of the elements decreases. B. The elements become stronger oxidizing agents. C. The elements become more volatile. D. The radius of the halide ion…

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Zadanie 16

Which ion is likely to form a coloured aqueous solution, based on its electron configuration? A. Ag⁺ B. Ti⁴⁺ C. Cd²⁺ D. Cr³⁺

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Zadanie 17

Which molecule contains a chiral centre? A. CH₃CH(NH₂)COOH B. (CH₃)₂CHCOOH C. CH₃CH₂CH(CH₃)CH₂CH₃ D. ClCH₂CH(OH)CH₂Cl

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Zadanie 18

Which is the low-resolution $\ce{^1H}$ NMR spectrum of methyl methanoate, HCOOCH₃? A. Spectrum A B. Spectrum B C. Spectrum C D. Spectrum D

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Zadanie 19

Which pair of compounds correctly illustrates the stated type of isomerism? A. Positional isomerism: CH₃CH₂CHO and CH₃COCH₃ B. Functional group isomerism: CH₃CH₂CH₂CH₂OH and CH₃CH(OH)CH₂CH₃ C. Cis-trans isomerism: the two compounds…

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Zadanie 20

The potential energy profile of a reaction is shown. Which reaction has this energy profile? A. Cl₂(g) → 2 Cl(g) B. CaCO₃(s) → CaO(s) + CO₂(g) C. N₂O₄(g) → 2 NO₂(g) D. 2 Mg(s) + O₂(g) → 2 MgO(s)

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Zadanie 21

What is the enthalpy change, in kJ mol⁻¹, for the formation of methanol from carbon monoxide and hydrogen? CO(g) + 2 H₂(g) → CH₃OH(l) A. −726 + 2(−286) − 283 B. −283 + 2(−286) + 726 C. −283 − 2(−286) + 726 D. −726 − 2(−286) − 283

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Zadanie 22

Which equation represents the enthalpy change of atomization, ΔH_at, of iodine? A. I₂(s) → I₂(g) B. I₂(g) → 2 I(g) C. $\ce{1/2I2(g) -> I(g)}$ D. $\ce{1/2I2(s) -> I(g)}$

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Zadanie 23

Which statement best describes an environmental consequence of using fossil fuels? A. The carbon dioxide released is completely absorbed by the oceans, so its concentration in the atmosphere does not change. B. Coal has a higher hydrogen to carbon ratio than…

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Zadanie 24

Which reaction is expected to have the largest decrease in entropy? A. 2 H₂S(g) + SO₂(g) → 3 S(s) + 2 H₂O(l) B. 2 C₄H₁₀(g) + 13 O₂(g) → 8 CO₂(g) + 10 H₂O(l) C. 4 NH₃(g) + 5 O₂(g) → 4 NO(g) + 6 H₂O(g) D. 2 CO(g) + O₂(g) → 2 CO₂(g)

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Zadanie 25

Equal volumes of the gases Q₂ and R₂ are mixed in a sealed container and react until one of them is used up, forming the gas QR₂. The volume of QR₂ formed, measured under the same conditions, is 50 cm³.…

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Zadanie 26

What volume of hydrogen, in cm³, is produced at STP when 0.810 g of aluminium reacts with an excess of hydrochloric acid? 2 Al(s) + 6 HCl(aq) → 2 AlCl₃(aq) + 3 H₂(g) Molar volume of an ideal gas at STP = 22.7 dm³ mol⁻¹ A. 341 B.…

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Zadanie 27

The dotted line shows the volume of hydrogen produced when an excess of magnesium ribbon is added to 50 cm³ of 2.0 mol dm⁻³ hydrochloric acid. Which curve shows the volume of hydrogen produced when the same excess of magnesium ribbon…

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Zadanie 28

Which reaction has the lowest activation energy? A. HBr(g) → H(g) + Br(g) B. 2 Cl(g) → Cl₂(g) C. CH₄(g) + Cl(g) → CH₃(g) + HCl(g) D. HBr(g) → H⁺(g) + Br⁻(g)

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Zadanie 29

The reaction 2 P → S + T was studied by measuring the initial rate at different initial concentrations of P. Which graph shows that the reaction is first order with respect to P? A. Graph A B. Graph B C. Graph C D. Graph D

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Zadanie 30

Which statement explains why a chemical equilibrium is described as dynamic? A. The forward and reverse reactions continue to take place at equal rates. B. The concentrations of the reactants and products keep changing until the reaction stops. C. The position…

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Zadanie 31

Nitrogen reacts with hydrogen to form ammonia. N₂(g) + 3 H₂(g) ⇌ 2 NH₃(g) A mixture of 1.50 mol of N₂(g) and 4.20 mol of H₂(g) was placed in a 1.00 dm³ container at a certain temperature. At equilibrium the mixture contained…

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Zadanie 32

In which reaction does water behave as a Brønsted–Lowry acid? A. H₂O(l) + HCl(g) → H₃O⁺(aq) + Cl⁻(aq) B. H₂O(g) + SO₃(g) → H₂SO₄(l) C. 2 H₂O(l) → 2 H₂(g) + O₂(g) D. H₂O(l) + NH₃(aq) → NH₄⁺(aq) + OH⁻(aq)

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Zadanie 33

Which aqueous solution has the highest pH? A. 0.010 mol dm⁻³ KNO₃ B. 0.010 mol dm⁻³ NH₄NO₃ C. 0.010 mol dm⁻³ CH₃COONa D. 0.010 mol dm⁻³ NaHSO₄

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Zadanie 34

Which half-equation represents the reduction of sulfuric acid to sulfur dioxide in acidic solution? A. H₂SO₄ + 2 H⁺ + 2 e⁻ → SO₂ + 2 H₂O B. H₂SO₄ + 4 H⁺ + 4 e⁻ → SO₂ + 2 H₂O C. H₂SO₄ + 2 H₂O → SO₂ + 6 H⁺ + 2 e⁻ D.…

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Zadanie 35

Which compounds are oxidized when heated with acidified potassium dichromate(VI) solution? I. CH₃CH₂C(CH₃)₂OH II. (CH₃)₂CHCH₂OH III. CH₃CH(OH)CH₃ A. I and II only B. I and III only C. II and III only D. I, II and III

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Zadanie 36

A student placed strips of the metals L, M and N in aqueous solutions containing the ions M²⁺, N²⁺ and L²⁺ respectively, as shown. The observations are given under each beaker. What is the order of increasing reactivity of the three…

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Zadanie 37

Which radical is most likely to form when one covalent bond in bromochlorodifluoromethane, CBrClF₂, is broken by ultraviolet light in the upper atmosphere? A. •CBrF₂ B. •CClF₂ C. •CBrClF D. •CBrClF₂

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Zadanie 38

Pent-2-ene undergoes a range of addition reactions. Which reagent and product are correctly matched? A. Reagent H₂, product pent-1-ene B. Reagent Br₂, product 2,3-dibromopentane C. Reagent H₂O, product pentan-1-ol D. Reagent HBr,…

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Zadanie 39

Which statements are correct for the complex ion [CoCl₄]²⁻? I. The oxidation state of cobalt is +4. II. The chloride ions act as Lewis bases. III. The coordination number of cobalt is 4. A. I and II only B. I and III only C. II and III only D. I, II…

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Zadanie 40

Which statement is correct about an S_N1 mechanism? A. The rate of reaction depends on the concentrations of both the halogenoalkane and the nucleophile. B. The rate-determining step forms a carbocation intermediate from a single molecule. C. The…