Chemistry HL Paper 1A, May 2025, TZ3

What is the number of hydrogen atoms in 0.0500 mol of hydrated magnesium sulfate, $\ce{MgSO4 * 7H2O}$? A. $3.01 \times 10^{22}$ B. $4.21 \times 10^{23}$ C. $2.11 \times 10^{23}$ D. $4.21 \times 10^{22}$

Which of the following could be the empirical formula of a compound with $M_\mathrm{r} = 70$? I. $\ce{CH2}$ II. $\ce{C4H6O}$ III. $\ce{C5H10}$ A. I and II only B. I and III only C. II and III only D. I, II and III

What volume of propane gas, in $\mathrm{cm^3}$, must be burned completely in oxygen to give 90 $\mathrm{cm^3}$ of carbon dioxide, all volumes being measured at the same temperature and pressure? $\ce{C3H8(g) + 5O2(g) -> 3CO2(g) + 4H2O(g)}$ A. 18 B. 30 C. 90 D.…

The mass spectrum of a sample of an element shows two peaks. What is the relative atomic mass of the element? A. 6.1 B. 6.5 C. 6.9 D. 7.0

How many electrons, at most, can be held in the fifth main energy level ($n = 5$) of an atom? A. 10 B. 25 C. 32 D. 50

Calcium ions and phosphate(V) ions combine to form an ionic compound. What is its formula? A. $\ce{CaPO4}$ B. $\ce{Ca2(PO4)3}$ C. $\ce{Ca3(PO4)2}$ D. $\ce{Ca3(PO3)2}$

A white crystalline solid has the properties shown in the table. Property Observation Melting point 770 °C Electrical conductivity of the solid none Electrical conductivity when molten good Solubility in water soluble Which structure is consistent with these…

Hydrogen fluoride boils at 20 °C, whereas hydrogen chloride boils at −85 °C. Which type of intermolecular force accounts for the much higher boiling point of hydrogen fluoride? A. Hydrogen bonding B. Dipole-dipole forces C. London (dispersion) forces D.…

The Lewis formula of the chlorate(VII) ion, $\ce{ClO4-}$, can be drawn with four single Cl–O bonds, as shown. What is the formal charge of the chlorine atom in this Lewis formula? A. −1 B. +1 C. +3 D. +7

Which hybridization is shown by the carbon atom and by the nitrogen atom in hydrogen cyanide, $\ce{HCN}$? A. C: $\mathrm{sp}$, N: $\mathrm{sp}$ B. C: $\mathrm{sp}$, N: $\mathrm{sp^2}$ C. C: $\mathrm{sp^2}$, N: $\mathrm{sp}$ D. C: $\mathrm{sp^2}$, N:…

Which list arranges the metals in order of increasing strength of metallic bonding (weakest first)? A. Rb, Mg, Na, Al B. Al, Mg, Na, Rb C. Rb, Na, Mg, Al D. Na, Rb, Al, Mg

Which element belongs to the f-block of the periodic table? A. Nd B. Fr C. Ta D. Pb

Which electron configuration is correct for a chromium atom, Cr, in its ground state? A. $\mathrm{[Ar]\,4s^1\,3d^5}$ B. $\mathrm{[Ar]\,4s^2\,3d^4}$ C. $\mathrm{[Ar]\,3d^6}$ D. $\mathrm{[Ar]\,4s^2\,4d^4}$

Which pair of elements reacts together most vigorously? A. Sodium and bromine B. Potassium and bromine C. Sodium and chlorine D. Potassium and chlorine

In which species does an atom have the oxidation state +5? I. $\ce{IF5}$ II. $\ce{H3PO4}$ III. $\ce{N2O4}$ A. I and II only B. I and III only C. II and III only D. I, II and III

An aqueous solution of nickel(II) sulfate, which contains the $\ce{[Ni(H2O)6]^2+}$ ion, is green. Which statement explains the origin of this colour? A. Red light is absorbed when electrons are promoted between the split d orbitals of the nickel ion. B. Red…

Which two functional groups occur in both molecule P and molecule Q? A. Amino and a benzene ring B. Hydroxyl and ester C. Hydroxyl and a benzene ring D. Amino and hydroxyl

The $\ce{^1H}$ NMR spectrum of an alcohol with molecular formula $\ce{C5H11OH}$ shows four signals with relative areas 6 : 4 : 1 : 1. Which alcohol is it? A. Pentan-1-ol B. Pentan-3-ol C. 2-methylbutan-2-ol D. 2,2-dimethylpropan-1-ol

How many chiral centres does the molecule shown contain? A. 1 B. 2 C. 3 D. 4

Which row correctly describes an endothermic reaction? A. The temperature of the surroundings rises and the products are more stable than the reactants. B. The temperature of the surroundings falls and the products are more stable than the reactants. C. The…

When 0.601 g of propan-1-ol is burned, the heat released raises the temperature of 250 $\mathrm{cm^3}$ of water by 8.00 K. What is the enthalpy of combustion of propan-1-ol, in $\mathrm{kJ\,mol^{-1}}$, calculated from these results? Specific heat capacity of…

The diagram shows an energy cycle for the formation of solid potassium bromide from its elements. Which energy change in the cycle represents the first ionization energy of potassium? A. $\Delta H_2$ B. $\Delta H_4$ C. $\Delta H_5$ D. $\Delta H_6$

For which of these changes is $\Delta S$ negative? A. $\ce{2SO2(g) + O2(g) -> 2SO3(g)}$ B. $\ce{NaNO3(s) -> NaNO3(aq)}$ C. $\ce{Zn(s) + 2HCl(aq) -> ZnCl2(aq) + H2(g)}$ D. $\ce{CuCO3(s) -> CuO(s) + CO2(g)}$

A reaction is spontaneous at low temperatures but becomes non-spontaneous when the temperature is raised. Which combination of signs of $\Delta H$ and $\Delta S$ is consistent with this behaviour? A. $\Delta H > 0$ and $\Delta S > 0$ B. $\Delta H < 0$ and…

Which route to chloroethane has an atom economy of 100 %? A. $\ce{C2H5OH + PCl5 -> C2H5Cl + POCl3 + HCl}$ B. $\ce{C2H6 + Cl2 -> C2H5Cl + HCl}$ C. $\ce{C2H5OH + HCl -> C2H5Cl + H2O}$ D. $\ce{C2H4 + HCl -> C2H5Cl}$

Which of the following could be used to follow the progress of the reaction between calcium carbonate and dilute nitric acid? $\ce{CaCO3(s) + 2HNO3(aq) -> Ca(NO3)2(aq) + H2O(l) + CO2(g)}$ I. A balance recording the mass of the open flask and its contents II. A…

The table shows how the initial rate of the reaction between X and Y depends on the concentrations of the reactants. Experiment $[\ce{X}]$ / $\mathrm{mol\,dm^{-3}}$ $[\ce{Y}]$ / $\mathrm{mol\,dm^{-3}}$ Initial rate / $\mathrm{mol\,dm^{-3}\,s^{-1}}$ 1 0.10 0.20…

A reaction has the rate equation below. What are the units of the rate constant $k$? rate $= k[\ce{A}]^2[\ce{B}][\ce{C}]^0$ A. $\mathrm{s^{-1}}$ B. $\mathrm{mol^{-1}\,dm^{3}\,s^{-1}}$ C. $\mathrm{mol^{-2}\,dm^{6}\,s^{-1}}$ D.…

Iron(III) ions and thiocyanate ions form a deep red complex ion in aqueous solution. $\ce{Fe^3+(aq) + SCN^-(aq) <=> [Fe(SCN)]^2+(aq)}$ Which of the following correctly predicts the effect of a change on this equilibrium? A. Adding iron(III) nitrate solution…

What amount of oxygen, in mol, is required to burn 8.72 g of butane, $\ce{C4H10(g)}$, completely? $M$(butane) = 58.14 $\mathrm{g\,mol^{-1}}$ A. 0.0231 B. 0.150 C. 0.975 D. 1.95

What is the pH of a 0.020 $\mathrm{mol\,dm^{-3}}$ solution of nitric acid, $\ce{HNO3(aq)}$? A. 1.0 B. 1.7 C. 2.0 D. 12.3

Which of these solutions has a pH greater than 7 at 25 °C? A. $[\ce{H+}] = 1.0 \times 10^{-5}\ \mathrm{mol\,dm^{-3}}$ B. $[\ce{OH-}] = 1.0 \times 10^{-10}\ \mathrm{mol\,dm^{-3}}$ C. $[\ce{H3O+}] = 1.0 \times 10^{-11}\ \mathrm{mol\,dm^{-3}}$ D.…

Which equation correctly represents a reaction of dilute sulfuric acid? A. $\ce{H2SO4 + MgCO3 -> MgSO4 + CO2 + H2O}$ B. $\ce{H2SO4 + 2Ag -> Ag2SO4 + H2}$ C. $\ce{H2SO4 + 2KOH -> K2SO4 + H2}$ D. $\ce{H2SO4 + 2NaHCO3 -> Na2SO4 + 2H2O}$

The table gives data for four bases at 298 K. Base $K_\mathrm{b}$ p$K_\mathrm{b}$ $\ce{N2H4}$ 5.90 $\ce{C2H5NH2}$ $5.6 \times 10^{-4}$ $\ce{C6H5NH2}$ 9.37 $\ce{C5H5N}$ $1.7 \times 10^{-9}$ Which base has the weakest conjugate acid? A. $\ce{N2H4}$ B.…

A buffer solution contains propanoic acid at 0.300 $\mathrm{mol\,dm^{-3}}$ and sodium propanoate at 0.600 $\mathrm{mol\,dm^{-3}}$. What is its pH? p$K_\mathrm{a}$(propanoic acid) = 4.87 A. 4.57 B. 4.87 C. 5.17 D. 5.47

Cadmium was added to separate solutions of silver nitrate and chromium(III) nitrate. $\ce{Cd(s) + 2AgNO3(aq) -> Cd(NO3)2(aq) + 2Ag(s)}$ $\ce{Cd(s) + Cr(NO3)3(aq)}$: no reaction Which list places the three metals in order from most reactive to least reactive?…

Molten lead(II) bromide, $\ce{PbBr2(l)}$, is electrolysed using inert electrodes. Which products form at the electrodes? A. Anode: $\ce{Br2}$, cathode: $\ce{Pb}$ B. Anode: $\ce{O2}$, cathode: $\ce{Pb}$ C. Anode: $\ce{Pb}$, cathode: $\ce{Br2}$ D. Anode:…

Reduction of which compound gives pentan-2-ol? A. Pentan-2-one B. Pentan-3-one C. Pentanal D. Pentanoic acid

The table shows standard electrode potentials for three metals. Half-equation $E^\ominus$ / V $\ce{Mn^2+(aq) + 2e- <=> Mn(s)}$ −1.18 $\ce{Cr^3+(aq) + 3e- <=> Cr(s)}$ −0.74 $\ce{Cd^2+(aq) + 2e- <=> Cd(s)}$ −0.40 Which combination undergoes a spontaneous…

Which species can act as the electrophile in a substitution reaction with benzene? A. $\ce{Br-}$ B. $\ce{Na+}$ C. $\ce{OH-}$ D. $\ce{Br+}$