Chemistry HL Paper 1A, November 2025, TZ3

Which term describes the change of state shown in the equation below? $\ce{I2(s) -> I2(g)}$ A. Deposition B. Melting C. Evaporation D. Sublimation

Which feature of the hydrogen emission spectrum shows that the spacing between the electron energy levels decreases as the energy of the levels increases? A. The lines within each series get closer together towards the high-frequency end B. The spectrum…

What is the total number of ions in 0.30 mol of iron(III) nitrate, $\ce{Fe(NO3)3}$? A. $0.30 \times 1 \times 6.02 \times 10^{23}$ B. $0.30 \times 3 \times 6.02 \times 10^{23}$ C. $0.30 \times 4 \times 6.02 \times 10^{23}$ D.…

0.30 $\mathrm{dm^3}$ of nitrogen is mixed with 0.60 $\mathrm{dm^3}$ of hydrogen and the mixture reacts as completely as possible. All gas volumes are measured at the same temperature and pressure. $\ce{N2(g) + 3H2(g) -> 2NH3(g)}$ What volume of ammonia, in…

An ideal gas is held in a rigid, sealed container at 27 °C, where its pressure is $P$ Pa. The container is then cooled to −3 °C. Which expression best describes the new pressure of the gas? A. Slightly less than $P$ B. Slightly more than $P$ C. One ninth of…

Which row correctly gives the electron domain geometry and the molecular geometry of sulfur dichloride, $\ce{SCl2}$? A. Trigonal planar electron domain geometry; bent molecular geometry B. Linear electron domain geometry; linear molecular geometry C.…

Which molecule has the largest net dipole moment? A. $\ce{SiF4}$ B. $\ce{CS2}$ C. $\ce{H2S}$ D. $\ce{H2O}$

Which statements about the allotropes of carbon are correct? I. Graphite conducts electricity because each carbon atom contributes one electron to a delocalized system. II. Diamond conducts electricity because it has a covalent network structure. III.…

What is the hybridization of the atoms labelled I, II and III in the molecule shown? A. I: $\mathrm{sp}$, II: $\mathrm{sp^3}$, III: $\mathrm{sp^3}$ B. I: $\mathrm{sp}$, II: $\mathrm{sp^2}$, III: $\mathrm{sp^3}$ C. I: $\mathrm{sp^2}$, II: $\mathrm{sp^3}$, III:…

A solid has a very high melting point, does not conduct electricity when solid or when molten, and is insoluble in water and in non-polar solvents. Which type of structure does the solid have? A. Ionic lattice B. Metallic lattice C. Covalent molecular D.…

What are the numbers of σ (sigma) and π (pi) bonds in one molecule of prop-2-ynal, $\ce{HC#CCHO}$? A. 5 σ and 3 π B. 3 σ and 3 π C. 3 σ and 5 π D. 6 σ and 2 π

Which of these elements is a non-metal found in the p-block of the periodic table? A. Bi B. Se C. Sc D. Cs

In which compound is the electrostatic attraction between the ions weakest? A. $\ce{MgO}$ B. $\ce{CaO}$ C. $\ce{CaS}$ D. $\ce{MgS}$

Which oxide reacts with water to give a solution with a pH greater than 7? A. $\ce{SO2}$ B. $\ce{P4O10}$ C. $\ce{Al2O3}$ D. $\ce{Na2O}$

Aqueous nickel(II) ions, $\ce{[Ni(H2O)6]^2+}$, appear green. Which statements correctly account for this colour? I. Red light is absorbed when an electron is promoted from the lower to the higher set of split d-orbitals. II. Green light is emitted when…

Which of these alkanes boils at the lowest temperature? A. $\ce{CH3CH2CH2CH2CH3}$ B. $\ce{C(CH3)4}$ C. $\ce{(CH3)2CHCH2CH3}$ D. $\ce{CH3CH2CH2CH2CH2CH3}$

Which of the following compounds show stereoisomerism? I. $\ce{CH3CH=CHCH3}$ II. $\ce{CH3CH(OH)CH2CH3}$ III. $\ce{(CH3)2C=CH2}$ A. I and II only B. I and III only C. II and III only D. I, II and III

Which is the correct IUPAC name for the compound shown? A. 2-methylpent-3-enoic acid B. 4-methylpent-2-enoic acid C. 4-methylpent-3-enoic acid D. 3-methylbut-1-enoic acid

When the equation for the complete combustion of 1 mol of pentan-1-ol, $\ce{C5H11OH}$, is balanced, what is the sum of all the coefficients? Unbalanced equation: $\ce{C5H11OH(l) + O2(g) -> CO2(g) + H2O(l)}$ A. 19 B. 19.5 C. 20 D. 39

The standard enthalpy changes of two reactions are given below. $\ce{N2(g) + O2(g) -> 2NO(g)}$ $\Delta H^\ominus = x\ \mathrm{kJ\,mol^{-1}}$ $\ce{2NO(g) + O2(g) -> 2NO2(g)}$ $\Delta H^\ominus = y\ \mathrm{kJ\,mol^{-1}}$ What is $\Delta H^\ominus$, in…

Which statement describes a disadvantage of using bioethanol rather than petrol (gasoline) as a fuel for cars? A. The carbon dioxide released when bioethanol burns was recently removed from the atmosphere by the crop B. Bioethanol releases less energy per…

Which set of products can be formed by the incomplete combustion of butane, $\ce{C4H10}$? A. $\ce{C}$, $\ce{CO}$ and $\ce{H2O}$ B. $\ce{CO2}$ and $\ce{H2O}$ only C. $\ce{CO}$ and $\ce{H2}$ only D. $\ce{C}$ and $\ce{H2}$ only

A sealed glass tube contains solid iodine in equilibrium with iodine vapour at constant temperature. Which of the following could be observed? A. The purple colour of the vapour gradually becomes more intense B. The total mass of the solid decreases steadily…

Sucrose, $\ce{C12H22O11}$, is hydrolysed with excess water and the glucose formed is then fermented. $\ce{C12H22O11(aq) + H2O(l) -> 2C6H12O6(aq)}$ $\ce{C6H12O6(aq) -> 2C2H5OH(aq) + 2CO2(g)}$ $M_\mathrm{r}$ of $\ce{C12H22O11}$ = 342.34 $M_\mathrm{r}$ of…

Equal volumes of nitrogen and hydrogen are mixed and react according to the equation below. The volumes of the two reactants are measured at intervals. $\ce{N2(g) + 3H2(g) -> 2NH3(g)}$ Which graph shows how the volumes of the two reactants change with time? A.…

The following mechanism has been proposed for the reaction between nitrogen(II) oxide and hydrogen. $\ce{2NO(g) <=> N2O2(g)}$ fast $\ce{N2O2(g) + H2(g) -> N2O(g) + H2O(g)}$ slow Which rate equation is consistent with this mechanism? A.…

Which of the following correctly describes the effect of a catalyst on a reaction? A. It increases the frequency of collisions between reactant particles B. It increases the proportion of collisions with energy greater than or equal to the activation energy C.…

Carbon monoxide reacts with chlorine to form phosgene, $\ce{COCl2}$. $\ce{CO(g) + Cl2(g) <=> COCl2(g)}$ $K = 2.75 \times 10^{3}$ at 45 °C $\Delta G = -RT\ln K$ $R = 8.31\ \mathrm{J\,K^{-1}\,mol^{-1}}$ What is the Gibbs energy change, $\Delta G$, in…

A mixture of 1 mol of nitrogen and 1 mol of oxygen is left to reach equilibrium at 25 °C. $\ce{N2(g) + O2(g) <=> 2NO(g)}$ $K = 4.5 \times 10^{-31}$ at 25 °C Which relationship holds in the equilibrium mixture? A. $[\ce{NO}] \ll [\ce{N2}]$ B.…

Sulfur dioxide and oxygen react reversibly: $\ce{2SO2(g) + O2(g) <=> 2SO3(g)}$ At a certain temperature the equilibrium constant is $K = 4.0$. A mixture at this temperature has the following concentrations, in $\mathrm{mol\,dm^{-3}}$: $[\ce{SO2}] = 0.50$,…

An aqueous solution at 298 K has a pH of 9.20. $K_\mathrm{w} = [\ce{H+}][\ce{OH-}] = 1.00 \times 10^{-14}$ at 298 K What is the hydroxide ion concentration of the solution, in $\mathrm{mol\,dm^{-3}}$? A. $6.31 \times 10^{-10}$ B. $1.58 \times 10^{-9}$ C.…

Which of these aqueous solutions has the highest pH? A. $0.10\ \mathrm{mol\,dm^{-3}}$ $\ce{HCl}$ B. $1.0\ \mathrm{mol\,dm^{-3}}$ $\ce{NH3}$ C. $0.10\ \mathrm{mol\,dm^{-3}}$ $\ce{KOH}$ D. $1.0\ \mathrm{mol\,dm^{-3}}$ $\ce{KOH}$

Which row identifies the oxidizing agent and the reducing agent in the reaction below? $\ce{3Cu(s) + 2NO3^-(aq) + 8H+(aq) -> 3Cu^2+(aq) + 2NO(g) + 4H2O(l)}$ A. Oxidizing agent: $\ce{Cu}$, reducing agent: $\ce{NO3^-}$ B. Oxidizing agent: $\ce{NO3^-}$, reducing…

Which statement correctly describes a type of electrochemical cell? A. A secondary cell operates as a voltaic cell when discharging and as an electrolytic cell when it is recharged B. A primary (voltaic) cell converts electrical energy into chemical energy C.…

A voltaic cell is made by connecting a manganese half-cell ($\ce{Mn(s)}$ in $\ce{Mn^2+(aq)}$) and a tin half-cell ($\ce{Sn(s)}$ in $\ce{Sn^2+(aq)}$) under standard conditions. $\ce{Mn^2+(aq) + 2e- <=> Mn(s)}$ $E^\ominus = -1.18\ \mathrm{V}$…

Which of the following is a correct description of the standard hydrogen electrode (SHE)? A. Hydrogen gas at 100 kPa is bubbled through a $1.0\ \mathrm{mol\,dm^{-3}}$ solution of sodium hydroxide B. Its electrode potential of 0.00 V is assigned by convention,…

A concentrated aqueous solution of potassium bromide is electrolysed between inert electrodes. Which products are mainly formed at the anode and at the cathode? A. Anode: $\ce{O2}$, cathode: $\ce{H2}$ B. Anode: $\ce{O2}$, cathode: $\ce{K}$ C. Anode:…

Which compound is formed when pentan-2-one, $\ce{CH3COCH2CH2CH3}$, is reduced? A. $\ce{CH3CH2CH2CH2CH2OH}$ B. $\ce{CH3CH2CH2CH2COOH}$ C. $\ce{CH3CH2CH2CH2CHO}$ D. $\ce{CH3CH(OH)CH2CH2CH3}$

What is the oxidation state of chromium in the complex $\ce{[Cr(NH3)4Cl2]Cl}$? A. +1 B. +2 C. +3 D. +7

Which compound is the major product when 2-methylpropene, $\ce{(CH3)2C=CH2}$, reacts with hydrogen chloride, $\ce{HCl}$? A. $\ce{(CH3)3CCl}$ B. $\ce{(CH3)2CHCH2Cl}$ C. $\ce{CH3CHClCH2CH3}$ D. $\ce{(CH3)2CClCH2Cl}$