Chemistry HL Paper 1A, May 2025, TZ2

A beaker contains a clear, colourless solution of potassium nitrate in water. What is the type of mixture and the best method of obtaining the solid salt from it? A. heterogeneous, by filtration B. heterogeneous, by evaporation C. homogeneous, by filtration D.…

Which property is the same for ammonia molecules containing deuterium, $\ce{ND3}$, and ordinary ammonia molecules, $\ce{NH3}$? A. Molar mass B. Molecular geometry C. Density of the gas at STP D. Rate of diffusion

What is the maximum number of electrons that can occupy the n = 4 main energy level? A. 8 B. 16 C. 18 D. 32

The successive ionization energies of an element are plotted against the number of the ionization. What is the group number of the element? A. 2 B. 3 C. 13 D. 14

What is the empirical formula of a compound with the following composition by mass? Element C H O Percentage by mass 54.5 % 9.1 % 36.4 % A. $\ce{C6HO4}$ B. $\ce{C4H8O}$ C. $\ce{C2H4O}$ D. $\ce{C4H8O2}$

What is the charge of the monatomic ion usually formed by the element with the following electron configuration? $\ce{[Ne] 3s^2 3p^4}$ A. 2+ B. 2− C. 4+ D. 6+

Which molecule is polar? A. $\ce{BF3}$ B. $\ce{NF3}$ C. $\ce{CCl4}$ D. $\ce{C2H4}$

A paper chromatogram is shown. The distances marked were measured along the paper. What is the retardation factor, $R_F$, of compound Y? A. 0.40 B. 0.60 C. 0.70 D. 1.67

What are the electron domain and molecular geometries of $\ce{ClF3}$? In each option the electron domain geometry is given first and the molecular geometry second. A. trigonal bipyramidal, trigonal planar B. trigonal bipyramidal, T-shaped C. trigonal planar,…

Methanoic acid, $\ce{HCOOH}$, has the structure shown. What are the hybridizations of the carbon atom, the oxygen atom of the C=O bond and the oxygen atom of the O–H bond? In each option the hybridizations are listed in that order. A. $\mathrm{sp^2}$,…

Which monomer produces this addition polymer? A. $\ce{CH2=CHCH2CH3}$ B. $\ce{CH3CH=CHCH3}$ C. $\ce{CH2=C(CH3)2}$ D. $\ce{CH2=CHCH=CH2}$

Why is the first ionization energy of sulfur greater than that of magnesium? A. The outer electrons of sulfur are further from the nucleus. B. Sulfur atoms have more occupied main energy levels. C. Sulfur atoms have a greater nuclear charge, while the…

The diagram shows an outline of the periodic table in which four elements of period 3 are labelled A, B, C and D. Which element forms an amphoteric oxide? A. Element A B. Element B C. Element C D. Element D

What is the oxidation state of chlorine in $\ce{Cl2O7}$? A. $-7$ B. $+3.5$ C. $+7$ D. $+14$

Which properties are typical of transition elements? I. Catalytic activity II. Formation of complex ions with ligands III. A single oxidation state in all their compounds A. I and II only B. I and III only C. II and III only D. I, II and III

What is the electron configuration of the $\ce{Co^2+}$ ion? A. $\ce{[Ar] 3d^7}$ B. $\ce{[Ar] 4s^2 3d^5}$ C. $\ce{[Ar] 4s^1 3d^6}$ D. $\ce{[Ar] 4s^2 3d^7}$

Which compound shows cis-trans isomerism? A. Compound A B. Compound B C. $\ce{CH2=C(CH3)2}$ D. $\ce{CH3CH=CH2}$

The energy profile below was recorded for a reaction. Which pair of statements is consistent with it? In each option the first statement compares the enthalpy of the products with that of the reactants and the second gives the sign of $\Delta H$. A. products…

A liquid fuel was burned in a spirit burner and the heat released was used to warm water in a metal calorimeter, as shown. Quantity Value Amount of fuel burned 0.0250 mol Mass of water 150 g Initial temperature of water 19.5 °C Final temperature of water 31.5…

What is the coefficient of oxygen when the equation for the complete combustion of butan-1-ol is balanced using the smallest whole numbers? The unbalanced equation is $\ce{C4H9OH + O2 -> CO2 + H2O}$. A. 4 B. 6 C. 7 D. 13

Which change results in a decrease in entropy? A. $\ce{2NaHCO3(s) -> Na2CO3(s) + H2O(g) + CO2(g)}$ B. $\ce{I2(s) -> I2(g)}$ C. $\ce{CO(g) + 2H2(g) -> CH3OH(l)}$ D. $\ce{KNO3(s) -> KNO3(aq)}$

Which condition applies to a reaction mixture that has reached equilibrium at constant temperature and pressure? A. $\Delta H = 0$ B. $\Delta G = 0$ C. $K = 1$ D. $\Delta S_\text{system} = 0$

What are the limiting reactant and the theoretical yield of hydrogen when 0.30 mol of aluminium reacts with 0.60 mol of hydrochloric acid? $\ce{2Al(s) + 6HCl(aq) -> 2AlCl3(aq) + 3H2(g)}$ In each option the limiting reactant is given first and the theoretical…

Which are units for rate of reaction? A. $\mathrm{s\,mol^{-1}\,dm^{3}}$ B. $\mathrm{mol\,dm^{-3}\,min}$ C. $\mathrm{mol\,dm^{-3}\,min^{-1}}$ D. $\mathrm{mol\,min^{-1}}$

Which changes increase the rate of the reaction? $\ce{CaCO3(s) + 2HCl(aq) -> CaCl2(aq) + H2O(l) + CO2(g)}$ I. Grinding the calcium carbonate into a fine powder II. Using a larger volume of hydrochloric acid of the same concentration III. Warming the…

Which species is an intermediate in the following reaction mechanism? $\ce{NO2(g) + NO2(g) -> NO3(g) + NO(g)}$ $\ce{NO3(g) + CO(g) -> NO2(g) + CO2(g)}$ A. $\ce{NO2}$ B. $\ce{NO3}$ C. $\ce{NO}$ D. $\ce{CO2}$

The rate of the reaction between propanone and iodine in acidic solution was measured at a fixed concentration of the acid catalyst. $\ce{CH3COCH3(aq) + I2(aq) -> CH3COCH2I(aq) + HI(aq)}$ $[\ce{CH3COCH3}]$ / $\mathrm{mol\,dm^{-3}}$ $[\ce{I2}]$ /…

Which statement about the rate constant, k, of an elementary reaction is correct? A. k increases when the temperature is raised, whether the reaction is exothermic or endothermic. B. k decreases when the temperature is raised for exothermic reactions. C. k…

The following system is at equilibrium. $\ce{H2(g) + I2(g) <=> 2HI(g)}$ $K = 54$ What is the value of the equilibrium constant, K, for the reaction $\ce{2HI(g) <=> H2(g) + I2(g)}$? A. $-54$ B. $\dfrac{1}{54}$ C. $\sqrt{54}$ D. $\dfrac{1}{\sqrt{54}}$

The container holding the equilibrium mixture below is compressed to half its volume while the temperature is kept constant. Which row gives the change in the amount of $\ce{PCl5}$ and the effect on the equilibrium constant, $K$?…

What is the conjugate acid of the hydrogen phosphate ion, $\ce{HPO4^2-}$? A. $\ce{PO4^3-}$ B. $\ce{H2PO4-}$ C. $\ce{H3PO4}$ D. $\ce{HPO3^2-}$

Which solution has a pH of 11.0 at 298 K? A. $10^{-3}\ \mathrm{mol\,dm^{-3}}$ $\ce{KOH(aq)}$ B. $10^{-11}\ \mathrm{mol\,dm^{-3}}$ $\ce{KOH(aq)}$ C. $10^{-3}\ \mathrm{mol\,dm^{-3}}$ $\ce{NH3(aq)}$ D. $10^{-3}\ \mathrm{mol\,dm^{-3}}$ $\ce{HCl(aq)}$

What is the main reason why nitric acid has a lower pH than ethanoic acid of the same concentration? A. Nitric acid is an oxidizing agent. B. Nitric acid ionizes to a greater extent in water. C. The conjugate base of nitric acid is stronger than that of…

Which salt forms a basic solution when dissolved in water? A. $\ce{KNO3}$ B. $\ce{NH4Br}$ C. $\ce{CH3COOK}$ D. $\ce{NaHSO4}$

What is the best indicator to use in the titration of propanoic acid with potassium hydroxide? A. Methyl orange, $\mathrm{p}K_\mathrm{a} = 3.7$ B. Bromocresol green, $\mathrm{p}K_\mathrm{a} = 4.7$ C. Bromothymol blue, $\mathrm{p}K_\mathrm{a} = 7.0$ D.…

In which compound does nitrogen have an oxidation state of +3? A. $\ce{NH3}$ B. $\ce{HNO2}$ C. $\ce{NO2}$ D. $\ce{HNO3}$

What is the standard cell potential, $E^\ominus_\text{cell}$, of the following cell? $\ce{Pb^2+(aq) + 2e- <=> Pb(s)}$ $E^\ominus = -0.13\ \mathrm{V}$ $\ce{Zn^2+(aq) + 2e- <=> Zn(s)}$ $E^\ominus = -0.76\ \mathrm{V}$ A. $-0.89\ \mathrm{V}$ B. $-0.63\ \mathrm{V}$…

Which change represents oxidation of the functional group? A. $\ce{CH3COCH3 -> CH3CH(OH)CH3}$ B. $\ce{CH3CH(OH)CH3 -> CH3COCH3}$ C. $\ce{CH3CH2COOH -> CH3CH2CHO}$ D. $\ce{CH3CH=CH2 -> CH3CH2CH3}$

What are the products of the electrolysis of concentrated aqueous sodium chloride using inert electrodes? In each option the product at the anode is given first and the product at the cathode second. A. chlorine gas, hydrogen gas B. chlorine gas, sodium metal…

Which equation represents a propagation step in the radical substitution of ethane by bromine? A. $\ce{Br2 -> 2Br•}$ B. $\ce{•C2H5 + Br• -> C2H5Br}$ C. $\ce{C2H6 + Br• -> C2H5Br + H•}$ D. $\ce{•C2H5 + Br2 -> C2H5Br + Br•}$