Chemistry HL Paper 2, May 2025, TZ3

Each indicator contains more than one benzene ring. (i) State one functional group, other than the phenyl group, that is present in all three indicators. (ii) Deduce the colour of light absorbed by bromothymol blue in acidic conditions and by bromophenol blue…

(i) Determine the molecular formula and the empirical formula of cresolphthalein. (ii) A simplified infrared (IR) spectrum of cresolphthalein is shown below. State the bonds responsible for the absorptions labelled P, Q and R. Use section 20 of the data…

Cresolphthalein is manufactured from 2-methylphenol, $\ce{CH3C6H4OH}$. State an equation that shows 2-methylphenol acting as a Brønsted–Lowry acid.

Cresolphthalein is a weak acid that can be represented as HIn. Using an equation, explain why the colour of a solution containing cresolphthalein depends on its pH.

The kinetic molecular theory describes matter as particles in constant motion. State and explain two physical properties of a gas using this model.

(i) An equilibrium mixture in a 25.0 $\mathrm{dm^3}$ reactor at 500 °C contains 15.0 mol $\ce{N2}$, 22.5 mol $\ce{H2}$ and 5.25 mol $\ce{NH3}$. Calculate the equilibrium constant, $K$, for the reaction. (ii) The volume of the reactor containing the equilibrium…

(i) Outline the way in which ammonia behaves as a Lewis base during the formation of the complex ion $\ce{[Ag(NH3)2]+(aq)}$. (ii) Determine the pH at 298 K of an aqueous ammonia solution of concentration 0.180 $\mathrm{mol\,dm^{-3}}$. Use section 1 of the data…

State the IUPAC name of compound Y.

Compound Y is chiral. Draw its two optical isomers, showing the three-dimensional arrangement of the groups around the chiral centre.

Calculate the percentage by mass of hydrogen in compound Y, giving your answer to four significant figures. Use section 7 of the data booklet.

The rate of the reaction between compound Y and aqueous sodium hydroxide depends on the concentrations of both reactants. (i) Explain the mechanism of this reaction, using curly arrows to show the movement of electron pairs. (ii) Explain why…

Draw the structural formula of one structural isomer of compound Y.

(i) Calculate, in $\mathrm{kJ\,mol^{-1}}$, the standard enthalpy change of this hydrogenation reaction using the enthalpy of combustion data in section 14 of the data booklet. (ii) The standard entropy change for this reaction is…

90.0 $\mathrm{cm^3}$ of buta-1,3-diene and 150.0 $\mathrm{cm^3}$ of hydrogen are mixed in a container at 450 K and 101 kPa and react to form butane only. Determine the maximum volume of butane that can be formed, measured at the same temperature and pressure.

(i) Draw the Lewis formula of buta-1,3-diene. (ii) State the hybridization of the carbon atoms in buta-1,3-diene.

During discharge, sodium atoms stored in the hard carbon are converted into sodium ions. (i) State the half-equation for the process taking place at the anode while the battery discharges. (ii) With reference to section 19 of the data booklet, comment on the…

The diagram below shows the battery connected to a charger. Annotate the diagram to show the direction in which electrons flow through the external wires while the battery is being recharged.

Suggest why banks of sodium-ion batteries are often installed alongside wind turbines.

A total charge of 1500.0 C flows through the external circuit during one discharge of the battery. Determine how many sodium ions are released at the anode. Use section 2 of the data booklet.

Kevlar is a condensation polymer. Deduce the structures of the two monomers from which Kevlar is made.

Kevlar owes its high strength to hydrogen bonds between neighbouring polymer chains. (i) Annotate the diagram below to show a hydrogen bond between the two chain sections, drawing the hydrogen bond as a dotted line. (ii) Outline how a hydrogen bond forms…

Discuss the melting points in the table below in terms of the bonding and/or intermolecular forces present in each substance. Substance Melting point / K Silicon dioxide (quartz) 1986 Poly(propene) 433

(i) State the products of the overall reaction. (ii) Sketch the energy profile for this reaction on the axes below. Label the reactants, the products, the transition states and the intermediate. (iii) Deduce the rate equation for the overall reaction.

Explain, using collision theory, why the rate of this reaction decreases when the temperature is lowered.

State the equation for the formation of glucose by photosynthesis.

(i) Outline two advantages of using biobutanol rather than petrol (gasoline) as a fuel for vehicles. (ii) Calculate, using the average bond enthalpies in section 12 of the data booklet, the enthalpy change in $\mathrm{kJ\,mol^{-1}}$ for the combustion of…

Calculate the rise in temperature of 400.0 $\mathrm{cm^3}$ of water heated by the complete combustion of 2.00 g of butan-1-ol, assuming that all the energy released is transferred to the water. Use sections 2 and 14 of the data booklet.

Explain the following trend in the atomic radii of three of the atoms in the urea molecule: H < N < C.

(i) State the electron configuration of a nitrogen atom. (ii) Draw the Lewis formula of ammonia. (iii) Deduce the electron domain geometry and the molecular geometry of the ammonia molecule. (iv) Explain why the ammonia molecule is polar.

In the atmosphere, nitrogen dioxide combines with rain water and oxygen to give nitric acid. State the equation for this reaction, including state symbols.