Chemistry HL Paper 2, November 2025, TZ3

Outline one reason why $\ce{SO2}$ is considered a pollutant.

A sample of flue gas has a volume of $2.5 \times 10^{-3}\ \mathrm{m^3}$ at 150 °C and $1.2 \times 10^5$ Pa, and contains 0.20 % $\ce{SO2}$ by volume. Using sections 1 and 2 of the data booklet, calculate the amount, in moles, of $\ce{SO2}$ present.

Outline why $\ce{SO2}$ shows a greater deviation from the ideal gas model than carbon dioxide, $\ce{CO2}$, does.

In the Claus process, used to recover sulfur from refinery gases, sulfur dioxide reacts with hydrogen sulfide, $\ce{H2S}$, to form sulfur. (i) State the oxidation state of sulfur in $\ce{SO2}$ and in the sulfur produced. (ii) Deduce the balanced equation for…

(i) In aqueous solution sulfuric acid transfers a proton to a water molecule, forming the hydroxonium ion, $\ce{H3O+}$. Annotate the structure of the hydroxonium ion to indicate the coordination bond. (ii) Write an equation for the reaction between excess…

(i) For the carbonate ion, draw its Lewis formula. (ii) Write the chemical formula of ammonium carbonate. (iii) State why all three C–O bonds in the carbonate ion are identical. (iv) Using section 11 of the data booklet, predict the length of the C–O bonds in…

Using section 19 of the data booklet, predict and explain what would be observed if zinc and silver metals were each added to a separate sample of blue copper(II) sulfate solution. Metal added Zn Ag Observations

Sulfurous acid has the formula $\ce{H2SO3}$. (i) Using the concept of formal charge, outline why Lewis formula 2 is the more stable, preferred structure. (ii) Write the formula for the conjugate base formed from sulfurous acid.

(i) If the reaction has a percentage yield of 80 %, calculate the mass, in g, of benzene that would be produced from 2.0 kg of cyclohexane. (ii) Calculate the atom economy for this reaction, as a percentage.

The forward reaction is endothermic, uses platinum as a catalyst, and takes place at 800 K. Sketch the reaction's energy profile both with and without the catalyst present, labelling the activation energies and $\Delta H$.

(i) Sketch the Maxwell–Boltzmann distribution curve for 298 K on the same axes as the 800 K curve. (ii) On the graph, annotate the position corresponding to the activation energy, $E_\mathrm{a}$. (iii) With reference to the graph, explain why a lower…

The forward reaction is first order with respect to cyclohexane. $\ce{C6H12(g) <=> C6H6(g) + 3H2(g)}$ (i) Sketch a graph showing how the rate varies with the concentration of cyclohexane. (ii) Deduce the reaction's rate equation, and state the units of the…

A compound used to make polymers, hexanedioic acid, can be produced by a series of reactions starting from cyclohexane. (i) Deduce how reactant A is related to hex-1-ene. (ii) For the C=O functional group present in intermediate C, state its structural…

Hexanoic acid, $\ce{CH3(CH2)4COOH}$, is a weak acid. The graph shows how the pH changes during the titration of a 20.0 $\mathrm{cm^3}$ aqueous solution of hexanoic acid with aqueous sodium hydroxide. (i) Deduce an expression for the equilibrium constant, $K$,…

(i) Describe how aqueous hexanoic acid and aqueous sodium hydroxide could be used to make a buffer solution. (ii) Predict the effect on the buffer's pH of adding a small amount of water.

(i) Hexanedioic acid reacts with hexane-1,6-diamine, $\ce{H2N(CH2)6NH2}$. State the type of polymer that is formed. (ii) Draw one repeating unit of the polymer's structure.

(i) State the type of reaction taking place, and identify the role played by $\ce{HI}$. (ii) Outline why molecules such as $\ce{HI}$ are able to attack ethene.

(i) Using section 12 of the data booklet, determine the standard enthalpy change of the reaction, in $\mathrm{kJ\,mol^{-1}}$. (ii) A value obtained from bond enthalpies is less accurate than one obtained from enthalpies of formation. State two reasons why.…

Iodoethane can react with aqueous hydroxide ions to produce ethanol. $\ce{CH3CH2I(l) + OH-(aq) -> CH3CH2OH(aq) + I-(aq)}$ (i) State what type of reaction this is. (ii) Using curly arrows to show the movement of electron pairs, sketch the mechanism of this…

Contrast the two isotopes in terms of atomic structure.

The sample produces the following mass spectrum. (i) Explain why the three peaks around $m/z$ 72 have different relative heights. (ii) From the sample, calculate the relative atomic mass of chlorine, giving your answer to two decimal places.

(i) Using sections 9 and 17 of the data booklet, and showing your working, deduce the type of bonding present in magnesium chloride, $\ce{MgCl2}$, and its percentage covalent character. (ii) Assuming purely ionic bonding, and using sections 9 and 12 of the…

Anhydrous nickel(II) chloride is yellow, whereas magnesium chloride is white. (i) State nickel's condensed electron configuration. (ii) In terms of electron configuration, state why nickel(II) chloride is a coloured compound. (iii) Nickel(II) chloride absorbs…

A steel object is electroplated with nickel, using an aqueous nickel(II) chloride electrolyte. (i) Deduce the half-equation for the reaction occurring at each electrode. Anode: Cathode: (ii) For the reaction between chlorine gas and aqueous potassium iodide…