CourseCourseConceptConceptDocumentDocument

IB Chemistry SL 1.1 Measuring Enthalpy Changes Questions

Use IB Chemistry SL questions to classify energy changes, interpret enthalpy profiles and calculate q and ΔH from calorimetry data under stated conditions.

Syllabus
First assessment 2025
Course
Chemistry SL
Level
SL

Exam points

  • Classify heat transfer and endothermic or exothermic changes from temperature evidence and the sign of ΔH.
  • Read or draw enthalpy profiles to compare levels, determine ΔH, identify activation energy and infer stability.
  • Calculate heat with q = mcΔT using mass, specific heat capacity, temperature change and consistent units.
  • Convert calorimetry heat to molar enthalpy using ΔH = −q/n, stoichiometry, sign and kJ mol⁻¹ units.
  • Evaluate calorimetry using heat-loss evidence, extrapolated temperatures and solution-property assumptions.

Covered syllabus points

1.1.1—Energy transfer1.1.2—Endothermic vs. exothermic1.1.3—Stability and energy1.1.4—Standard enthalpy change (ΔH⦵)

Question 1

[Maximum number: 1]

The increased concentration of carbon dioxide in the atmosphere is thought to result from the increased combustion of fossil fuels such as petroleum.

Outline why the energy available from an engine will be less than these theoretical values.

Question 2

[Maximum number: 1]

Chlorine occurs in Group 7, the halogens.

Chloroethene, H2C=CHCl\mathrm{H}_{2} \mathrm{C}=\mathrm{CHCl}, the monomer used in the polymerization reaction in the manufacture of the polymer poly(chloroethene), PVC, can be synthesized in the following two-stage reaction pathway.

Stage 1: C2H4( g)+Cl2( g)→ClCH2CH2Cl(g)\quad \mathrm{C}_{2} \mathrm{H}_{4}(\mathrm{~g})+\mathrm{Cl}_{2}(\mathrm{~g}) \rightarrow \mathrm{ClCH}_{2} \mathrm{CH}_{2} \mathrm{Cl}(\mathrm{g})

Stage 2: ClCH2CH2Cl(g)→H2C=CHCl(g)+HCl(g)\quad \mathrm{ClCH}_{2} \mathrm{CH}_{2} \mathrm{Cl}(\mathrm{g}) \rightarrow \mathrm{H}_{2} \mathrm{C}=\mathrm{CHCl}(\mathrm{g})+\mathrm{HCl}(\mathrm{g})

State whether the reaction given in stage 1 is exothermic or endothermic.

Question 3

[Maximum number: 3]

Phenylethene (styrene) is produced from ethylbenzene in a gas-phase equilibrium.

Figure for Question 3 — IB Chemistry SL

The forward reaction is endothermic, uses iron(III) oxide as a catalyst, and takes place at 900 K .

Sketch the energy profile for the reaction, both with and without the catalyst, labelling ΔH\Delta H and the activation energies.

Figure for Question 3 — IB Chemistry SL
All question bank results loaded